Merge branch 'release' of github.com:aspnet/Razor into release

build.cmd

@@ -19,10 +19,10 @@ IF EXIST packages\KoreBuild goto run
 .nuget\NuGet.exe install KoreBuild -ExcludeVersion -o packages -nocache -pre
 .nuget\NuGet.exe install Sake -version 0.2 -o packages -ExcludeVersion
 
-IF "%SKIP_KRE_INSTALL%"=="1" goto run
-CALL packages\KoreBuild\build\kvm upgrade -runtime CLR -x86
-CALL packages\KoreBuild\build\kvm install default -runtime CoreCLR -x86
+IF "%SKIP_DOTNET_INSTALL%"=="1" goto run
+CALL packages\KoreBuild\build\dotnetsdk upgrade -runtime CLR -x86
+CALL packages\KoreBuild\build\dotnetsdk install default -runtime CoreCLR -x86
 
 :run
-CALL packages\KoreBuild\build\kvm use default -runtime CLR -x86
+CALL packages\KoreBuild\build\dotnetsdk use default -runtime CLR -x86
 packages\Sake\tools\Sake.exe -I packages\KoreBuild\build -f makefile.shade %*

build.sh

@@ -28,11 +28,11 @@ if test ! -d packages/KoreBuild; then
 fi
 
 if ! type k > /dev/null 2>&1; then
-    source packages/KoreBuild/build/kvm.sh
+    source packages/KoreBuild/build/dotnetsdk.sh
 fi
 
 if ! type k > /dev/null 2>&1; then
-    kvm upgrade
+    dotnetsdk upgrade
 fi
 
 mono packages/Sake/tools/Sake.exe -I packages/KoreBuild/build -f makefile.shade "$@"

src/Microsoft.AspNet.Razor.Runtime/Properties/Resources.Designer.cs

@@ -81,17 +81,17 @@ namespace Microsoft.AspNet.Razor.Runtime
         /// <summary>
         /// Parameter {0} must not contain null tag names.
         /// </summary>
-        internal static string TagNameAttribute_AdditionalTagsCannotContainNull
+        internal static string HtmlElementNameAttribute_AdditionalTagsCannotContainNull
         {
-            get { return GetString("TagNameAttribute_AdditionalTagsCannotContainNull"); }
+            get { return GetString("HtmlElementNameAttribute_AdditionalTagsCannotContainNull"); }
         }
 
         /// <summary>
         /// Parameter {0} must not contain null tag names.
         /// </summary>
-        internal static string FormatTagNameAttribute_AdditionalTagsCannotContainNull(object p0)
+        internal static string FormatHtmlElementNameAttribute_AdditionalTagsCannotContainNull(object p0)
         {
-            return string.Format(CultureInfo.CurrentCulture, GetString("TagNameAttribute_AdditionalTagsCannotContainNull"), p0);
+            return string.Format(CultureInfo.CurrentCulture, GetString("HtmlElementNameAttribute_AdditionalTagsCannotContainNull"), p0);
         }
 
         /// <summary>

src/Microsoft.AspNet.Razor.Runtime/Resources.resx

@@ -131,7 +131,7 @@
   <data name="ScopeManager_EndCannotBeCalledWithoutACallToBegin" xml:space="preserve">
     <value>Must call '{2}.{1}' before calling '{2}.{0}'.</value>
   </data>
-  <data name="TagNameAttribute_AdditionalTagsCannotContainNull" xml:space="preserve">
+  <data name="HtmlElementNameAttribute_AdditionalTagsCannotContainNull" xml:space="preserve">
     <value>Parameter {0} must not contain null tag names.</value>
   </data>
   <data name="ArgumentCannotBeNullOrEmpty" xml:space="preserve">

src/Microsoft.AspNet.Razor.Runtime/TagHelpers/ContentBehaviorAttribute.cs

@@ -1,31 +0,0 @@
-// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
-// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
-
-using System;
-using Microsoft.AspNet.Razor.TagHelpers;
-
-namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
-{
-    /// <summary>
-    /// Used to override <see cref="ITagHelper"/>'s behavior when its
-    /// <see cref="ITagHelper.ProcessAsync"/> is invoked.
-    /// </summary>
-    [AttributeUsage(AttributeTargets.Class, AllowMultiple = false, Inherited = false)]
-    public sealed class ContentBehaviorAttribute : Attribute
-    {
-        /// <summary>
-        /// Instantiates a new instance of the <see cref="ContentBehaviorAttribute"/> class.
-        /// </summary>
-        /// <param name="contentBehavior">The <see cref="Razor.TagHelpers.ContentBehavior"/> for the
-        /// <see cref="ITagHelper"/>.</param>
-        public ContentBehaviorAttribute(ContentBehavior contentBehavior)
-        {
-            ContentBehavior = contentBehavior;
-        }
-
-        /// <summary>
-        /// <see cref="Razor.TagHelpers.ContentBehavior"/> for the <see cref="ITagHelper"/>.
-        /// </summary>
-        public ContentBehavior ContentBehavior { get; private set; }
-    }
-}

src/Microsoft.AspNet.Razor.Runtime/TagHelpers/HtmlElementNameAttribute.cs

@@ -11,29 +11,29 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
     /// Used to override a <see cref="ITagHelper"/>'s default tag name target.
     /// </summary>
     [AttributeUsage(AttributeTargets.Class, AllowMultiple = true, Inherited = false)]
-    public sealed class TagNameAttribute : Attribute
+    public sealed class HtmlElementNameAttribute : Attribute
     {
         /// <summary>
-        /// Instantiates a new instance of the <see cref="TagNameAttribute"/> class.
+        /// Instantiates a new instance of the <see cref="HtmlElementNameAttribute"/> class.
         /// </summary>
         /// <param name="tag">The HTML tag name for the <see cref="TagHelper"/> to target.</param>
-        public TagNameAttribute([NotNull] string tag)
+        public HtmlElementNameAttribute([NotNull] string tag)
         {
             Tags = new[] { tag };
         }
 
         /// <summary>
-        /// Instantiates a new instance of the <see cref="TagNameAttribute"/> class.
+        /// Instantiates a new instance of the <see cref="HtmlElementNameAttribute"/> class.
         /// </summary>
         /// <param name="tag">The HTML tag name for the <see cref="TagHelper"/> to target.</param>
         /// <param name="additionalTags">Additional HTML tag names for the <see cref="TagHelper"/> to target.</param>
-        public TagNameAttribute([NotNull] string tag, [NotNull] params string[] additionalTags)
+        public HtmlElementNameAttribute([NotNull] string tag, [NotNull] params string[] additionalTags)
         {
             if (additionalTags.Contains(null))
             {
                 throw new ArgumentNullException(
                     nameof(additionalTags),
-                    Resources.FormatTagNameAttribute_AdditionalTagsCannotContainNull(nameof(additionalTags)));
+                    Resources.FormatHtmlElementNameAttribute_AdditionalTagsCannotContainNull(nameof(additionalTags)));
             };
 
             var allTags = new List<string>(additionalTags);

src/Microsoft.AspNet.Razor.Runtime/TagHelpers/TagHelperContext.cs

@@ -1,7 +1,9 @@
 // Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using System.Collections.Generic;
+using System.Threading.Tasks;
 
 namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
 {
@@ -10,18 +12,42 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
     /// </summary>
     public class TagHelperContext
     {
+        private readonly Func<Task<string>> _getChildContentAsync;
+
         /// <summary>
         /// Instantiates a new <see cref="TagHelperContext"/>.
         /// </summary>
         /// <param name="allAttributes">Every attribute associated with the current HTML element.</param>
-        public TagHelperContext([NotNull] IDictionary<string, object> allAttributes)
+        /// <param name="uniqueId">The unique identifier for the source element this <see cref="TagHelperContext" /> 
+        /// applies to.</param>
+        /// <param name="getChildContentAsync">A delegate used to execute and retrieve the rendered child content 
+        /// asynchronously.</param>
+        public TagHelperContext([NotNull] IDictionary<string, object> allAttributes,
+                                [NotNull] string uniqueId,
+                                [NotNull] Func<Task<string>> getChildContentAsync)
         {
             AllAttributes = allAttributes;
+            UniqueId = uniqueId;
+            _getChildContentAsync = getChildContentAsync;
         }
 
         /// <summary>
         /// Every attribute associated with the current HTML element.
         /// </summary>
-        public IDictionary<string, object> AllAttributes { get; private set; }
+        public IDictionary<string, object> AllAttributes { get; }
+
+        /// <summary>
+        /// An identifier unique to the HTML element this context is for.
+        /// </summary>
+        public string UniqueId { get; }
+
+        /// <summary>
+        /// A delegate used to execute and retrieve the rendered child content asynchronously.
+        /// </summary>
+        /// <returns>A <see cref="Task"/> that when executed returns content rendered by children.</returns>
+        public Task<string> GetChildContentAsync()
+        {
+            return _getChildContentAsync();
+        }
     }
 }

src/Microsoft.AspNet.Razor.Runtime/TagHelpers/TagHelperDescriptorFactory.cs

@@ -5,6 +5,7 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Reflection;
+using System.Text.RegularExpressions;
 using Microsoft.AspNet.Razor.TagHelpers;
 
 namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
@@ -15,6 +16,14 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
     public static class TagHelperDescriptorFactory
     {
         private const string TagHelperNameEnding = "TagHelper";
+        private const string HtmlCaseRegexReplacement = "-$1$2";
+
+        // This matches the following AFTER the start of the input string (MATCH).
+        // Any letter/number followed by an uppercase letter then lowercase letter: 1(Aa), a(Aa), A(Aa)
+        // Any lowercase letter followed by an uppercase letter: a(A)
+        // Each match is then prefixed by a "-" via the ToHtmlCase method.
+        private static readonly Regex HtmlCaseRegex =
+            new Regex("(?<!^)((?<=[a-zA-Z0-9])[A-Z][a-z])|((?<=[a-z])[A-Z])", RegexOptions.None);
 
         // TODO: Investigate if we should cache TagHelperDescriptors for types:
         // https://github.com/aspnet/Razor/issues/165
@@ -29,21 +38,19 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             var tagNames = GetTagNames(type);
             var typeName = type.FullName;
             var attributeDescriptors = GetAttributeDescriptors(type);
-            var contentBehavior = GetContentBehavior(type);
             var assemblyName = type.GetTypeInfo().Assembly.GetName().Name;
 
             return tagNames.Select(tagName =>
                 new TagHelperDescriptor(tagName,
                                         typeName,
                                         assemblyName,
-                                        contentBehavior,
                                         attributeDescriptors));
         }
 
         private static IEnumerable<string> GetTagNames(Type tagHelperType)
         {
             var typeInfo = tagHelperType.GetTypeInfo();
-            var attributes = typeInfo.GetCustomAttributes<TagNameAttribute>(inherit: false);
+            var attributes = typeInfo.GetCustomAttributes<HtmlElementNameAttribute>(inherit: false);
 
             // If there isn't an attribute specifying the tag name derive it from the name
             if (!attributes.Any())
@@ -55,7 +62,7 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
                     name = name.Substring(0, name.Length - TagHelperNameEnding.Length);
                 }
 
-                return new[] { name };
+                return new[] { ToHtmlCase(name) };
             }
 
             // Remove duplicate tag names.
@@ -75,21 +82,11 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             var attributeNameAttribute = property.GetCustomAttribute<HtmlAttributeNameAttribute>(inherit: false);
             var attributeName = attributeNameAttribute != null ?
                                 attributeNameAttribute.Name :
-                                property.Name;
+                                ToHtmlCase(property.Name);
 
             return new TagHelperAttributeDescriptor(attributeName, property.Name, property.PropertyType.FullName);
         }
 
-        private static ContentBehavior GetContentBehavior(Type type)
-        {
-            var typeInfo = type.GetTypeInfo();
-            var contentBehaviorAttribute = typeInfo.GetCustomAttribute<ContentBehaviorAttribute>(inherit: false);
-
-            return contentBehaviorAttribute != null ?
-                contentBehaviorAttribute.ContentBehavior :
-                ContentBehavior.None;
-        }
-
         private static bool IsValidProperty(PropertyInfo property)
         {
             return property.GetMethod != null &&
@@ -97,5 +94,22 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
                    property.SetMethod != null &&
                    property.SetMethod.IsPublic;
         }
+
+        /// <summary>
+        /// Converts from pascal/camel case to lower kebab-case.
+        /// </summary>
+        /// <example>
+        /// SomeThing => some-thing
+        /// capsONInside => caps-on-inside
+        /// CAPSOnOUTSIDE => caps-on-outside
+        /// ALLCAPS => allcaps
+        /// One1Two2Three3 => one1-two2-three3
+        /// ONE1TWO2THREE3 => one1two2three3
+        /// First_Second_ThirdHi => first_second_third-hi
+        /// </example>
+        private static string ToHtmlCase(string name)
+        {
+            return HtmlCaseRegex.Replace(name, HtmlCaseRegexReplacement).ToLowerInvariant();
+        }
     }
 }

src/Microsoft.AspNet.Razor.Runtime/TagHelpers/TagHelperExecutionContext.cs

@@ -3,6 +3,8 @@
 
 using System;
 using System.Collections.Generic;
+using System.IO;
+using System.Threading.Tasks;
 
 namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
 {
@@ -12,28 +14,73 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
     public class TagHelperExecutionContext
     {
         private readonly List<ITagHelper> _tagHelpers;
+        private readonly Func<Task> _executeChildContentAsync;
+        private readonly Action _startWritingScope;
+        private readonly Func<TextWriter> _endWritingScope;
+        private string _childContent;
+
+        /// <summary>
+        /// Internal for testing purposes only.
+        /// </summary>
+        internal TagHelperExecutionContext(string tagName)
+            : this(tagName,
+                   uniqueId: string.Empty,
+                   executeChildContentAsync: async () => await Task.FromResult(result: true),
+                   startWritingScope: () => { },
+                   endWritingScope: () => new StringWriter())
+        {
+        }
 
         /// <summary>
         /// Instantiates a new <see cref="TagHelperExecutionContext"/>.
         /// </summary>
         /// <param name="tagName">The HTML tag name in the Razor source.</param>
-        public TagHelperExecutionContext([NotNull] string tagName)
+        /// <param name="uniqueId">An identifier unique to the HTML element this context is for.</param>
+        /// <param name="executeChildContentAsync">A delegate used to execute the child content asynchronously.</param>
+        /// <param name="startWritingScope">A delegate used to start a writing scope in a Razor page.</param>
+        /// <param name="endWritingScope">A delegate used to end a writing scope in a Razor page.</param>
+        public TagHelperExecutionContext([NotNull] string tagName,
+                                         [NotNull] string uniqueId,
+                                         [NotNull] Func<Task> executeChildContentAsync,
+                                         [NotNull] Action startWritingScope,
+                                         [NotNull] Func<TextWriter> endWritingScope)
         {
+            _tagHelpers = new List<ITagHelper>();
+            _executeChildContentAsync = executeChildContentAsync;
+            _startWritingScope = startWritingScope;
+            _endWritingScope = endWritingScope;
+
             AllAttributes = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
             HTMLAttributes = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
-            _tagHelpers = new List<ITagHelper>();
             TagName = tagName;
+            UniqueId = uniqueId;
+        }
+
+        /// <summary>
+        /// Indicates if <see cref="GetChildContentAsync"/> has been called.
+        /// </summary>
+        public bool ChildContentRetrieved
+        {
+            get
+            {
+                return _childContent != null;
+            }
         }
 
         /// <summary>
         /// HTML attributes.
         /// </summary>
-        public IDictionary<string, string> HTMLAttributes { get; private set; }
+        public IDictionary<string, string> HTMLAttributes { get; }
 
         /// <summary>
         /// <see cref="ITagHelper"/> bound attributes and HTML attributes.
         /// </summary>
-        public IDictionary<string, object> AllAttributes { get; private set; }
+        public IDictionary<string, object> AllAttributes { get; }
+
+        /// <summary>
+        /// An identifier unique to the HTML element this context is for.
+        /// </summary>
+        public string UniqueId { get; }
 
         /// <summary>
         /// <see cref="ITagHelper"/>s that should be run.
@@ -49,7 +96,7 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
         /// <summary>
         /// The HTML tag name in the Razor source.
         /// </summary>
-        public string TagName { get; private set; }
+        public string TagName { get; }
 
         /// <summary>
         /// The <see cref="ITagHelper"/>s' output.
@@ -85,5 +132,34 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
         {
             AllAttributes.Add(name, value);
         }
+
+        /// <summary>
+        /// Executes the child content asynchronously.
+        /// </summary>
+        /// <returns>A <see cref="Task"/> which on completion executes all child content.</returns>
+        public Task ExecuteChildContentAsync()
+        {
+            return _executeChildContentAsync();
+        }
+
+        /// <summary>
+        /// Execute and retrieve the rendered child content asynchronously.
+        /// </summary>
+        /// <returns>A <see cref="Task"/> that on completion returns the rendered child content.</returns>
+        /// <remarks>
+        /// Child content is only executed once. Successive calls to this method or successive executions of the 
+        /// returned <see cref="Task{string}"/> return a cached result.
+        /// </remarks>
+        public async Task<string> GetChildContentAsync()
+        {
+            if (_childContent == null)
+            {
+                _startWritingScope();
+                await _executeChildContentAsync();
+                _childContent = _endWritingScope().ToString();
+            }
+
+            return _childContent;
+        }
     }
 }

src/Microsoft.AspNet.Razor.Runtime/TagHelpers/TagHelperOutput.cs

@@ -15,7 +15,7 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
     public class TagHelperOutput
     {
         private string _content;
-        private string _tagName;
+        private bool _contentSet;
 
         // Internal for testing
         internal TagHelperOutput(string tagName)
@@ -24,48 +24,39 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             Attributes = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
         }
 
-        // Internal for testing
-        internal TagHelperOutput(string tagName, [NotNull] IDictionary<string, string> attributes)
-            : this(tagName, attributes, string.Empty)
-        {
-        }
-
         /// <summary>
         /// Instantiates a new instance of <see cref="TagHelperOutput"/>.
         /// </summary>
         /// <param name="tagName">The HTML element's tag name.</param>
         /// <param name="attributes">The HTML attributes.</param>
-        /// <param name="content">The HTML element's content.</param>
-        public TagHelperOutput(string tagName,
-                               [NotNull] IDictionary<string, string> attributes,
-                               string content)
+        public TagHelperOutput(string tagName, [NotNull] IDictionary<string, string> attributes)
         {
             TagName = tagName;
-            Content = content;
             Attributes = new Dictionary<string, string>(attributes, StringComparer.OrdinalIgnoreCase);
+            PreContent = string.Empty;
+            _content = string.Empty;
+            PostContent = string.Empty;
         }
 
         /// <summary>
         /// The HTML element's tag name.
         /// </summary>
         /// <remarks>
-        /// A whitespace value results in no start or end tag being rendered.
+        /// A whitespace or <c>null</c> value results in no start or end tag being rendered.
         /// </remarks>
-        public string TagName
-        {
-            get
-            {
-                return _tagName;
-            }
-            set
-            {
-                _tagName = value ?? string.Empty;
-            }
-        }
+        public string TagName { get; set; }
 
         /// <summary>
-        /// The HTML element's content.
+        /// The HTML element's pre content.
         /// </summary>
+        /// <remarks>Value is prepended to the <see cref="ITagHelper"/>'s final output.</remarks>
+        public string PreContent { get; set; }
+
+        /// <summary>
+        /// The HTML element's main content.
+        /// </summary>
+        /// <remarks>Value occurs in the <see cref="ITagHelper"/>'s final output after <see cref="PreContent"/> and 
+        /// before <see cref="PostContent"/></remarks>
         public string Content
         {
             get
@@ -74,7 +65,25 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             }
             set
             {
-                _content = value ?? string.Empty;
+                _contentSet = true;
+                _content = value;
+            }
+        }
+
+        /// <summary>
+        /// The HTML element's post content.
+        /// </summary>
+        /// <remarks>Value is appended to the <see cref="ITagHelper"/>'s final output.</remarks>
+        public string PostContent { get; set; }
+
+        /// <summary>
+        /// <c>true</c> if <see cref="Content"/> has been set, <c>false</c> otherwise.
+        /// </summary>
+        public bool ContentSet
+        {
+            get
+            {
+                return _contentSet;
             }
         }
 
@@ -86,7 +95,7 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
         /// <summary>
         /// The HTML element's attributes.
         /// </summary>
-        public IDictionary<string, string> Attributes { get; private set; }
+        public IDictionary<string, string> Attributes { get; }
 
         /// <summary>
         /// Generates the <see cref="TagHelperOutput"/>'s start tag.
@@ -126,6 +135,22 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             return sb.ToString();
         }
 
+        /// <summary>
+        /// Generates the <see cref="TagHelperOutput"/>'s <see cref="PreContent"/>.
+        /// </summary>
+        /// <returns><c>string.Empty</c> if <see cref="SelfClosing"/> is <c>true</c>. <see cref="PreContent"/> 
+        /// otherwise.
+        /// </returns>
+        public string GeneratePreContent()
+        {
+            if (SelfClosing)
+            {
+                return string.Empty;
+            }
+
+            return PreContent;
+        }
+
         /// <summary>
         /// Generates the <see cref="TagHelperOutput"/>'s body.
         /// </summary>
@@ -141,6 +166,22 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             return Content;
         }
 
+        /// <summary>
+        /// Generates the <see cref="TagHelperOutput"/>'s <see cref="PostContent"/>.
+        /// </summary>
+        /// <returns><c>string.Empty</c> if <see cref="SelfClosing"/> is <c>true</c>. <see cref="PostContent"/> 
+        /// otherwise.
+        /// </returns>
+        public string GeneratePostContent()
+        {
+            if (SelfClosing)
+            {
+                return string.Empty;
+            }
+
+            return PostContent;
+        }
+
         /// <summary>
         /// Generates the <see cref="TagHelperOutput"/>'s end tag.
         /// </summary>
@@ -155,5 +196,20 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
 
             return string.Format(CultureInfo.InvariantCulture, "</{0}>", TagName);
         }
+
+        /// <summary>
+        /// Changes <see cref="TagHelperOutput"/> to generate nothing.
+        /// </summary>
+        /// <remarks>
+        /// Sets <see cref="TagName"/>, <see cref="PreContent"/>, <see cref="Content"/>, and <see cref="PostContent"/> 
+        /// to <c>null</c> to suppress output.
+        /// </remarks>
+        public void SuppressOutput()
+        {
+            TagName = null;
+            PreContent = null;
+            Content = null;
+            PostContent = null;
+        }
     }
 }

src/Microsoft.AspNet.Razor.Runtime/TagHelpers/TagHelperRunner.cs

@@ -1,7 +1,6 @@
 // Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-using System.IO;
 using System.Threading.Tasks;
 
 namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
@@ -14,33 +13,17 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
         /// <summary>
         /// Calls the <see cref="ITagHelper.ProcessAsync"/> method on <see cref="ITagHelper"/>s.
         /// </summary>
-        /// <param name="context">Contains information associated with running <see cref="ITagHelper"/>s.</param>
+        /// <param name="executionContext">Contains information associated with running <see cref="ITagHelper"/>s.
+        /// </param>
         /// <returns>Resulting <see cref="TagHelperOutput"/> from processing all of the
-        /// <paramref name="context"/>'s <see cref="ITagHelper"/>s.</returns>
-        public async Task<TagHelperOutput> RunAsync([NotNull] TagHelperExecutionContext context)
+        /// <paramref name="executionContext"/>'s <see cref="ITagHelper"/>s.</returns>
+        public async Task<TagHelperOutput> RunAsync([NotNull] TagHelperExecutionContext executionContext)
         {
-            return await RunAsyncCore(context, string.Empty);
-        }
-
-        /// <summary>
-        /// Calls the <see cref="ITagHelper.ProcessAsync"/> method on <see cref="ITagHelper"/>s.
-        /// </summary>
-        /// <param name="context">Contains information associated with running <see cref="ITagHelper"/>s.</param>
-        /// <param name="bufferedBody">Contains the buffered content of the current HTML tag.</param>
-        /// <returns>Resulting <see cref="TagHelperOutput"/> from processing all of the
-        /// <paramref name="context"/>'s <see cref="ITagHelper"/>s.</returns>
-        public async Task<TagHelperOutput> RunAsync([NotNull] TagHelperExecutionContext context,
-                                                    [NotNull] TextWriter bufferedBody)
-        {
-            return await RunAsyncCore(context, bufferedBody.ToString());
-        }
-
-        private async Task<TagHelperOutput> RunAsyncCore(TagHelperExecutionContext executionContext, string outputContent)
-        {
-            var tagHelperContext = new TagHelperContext(executionContext.AllAttributes);
-            var tagHelperOutput = new TagHelperOutput(executionContext.TagName,
-                                                      executionContext.HTMLAttributes,
-                                                      outputContent);
+            var tagHelperContext = new TagHelperContext(
+                executionContext.AllAttributes,
+                executionContext.UniqueId,
+                executionContext.GetChildContentAsync);
+            var tagHelperOutput = new TagHelperOutput(executionContext.TagName, executionContext.HTMLAttributes);
 
             foreach (var tagHelper in executionContext.TagHelpers)
             {

src/Microsoft.AspNet.Razor.Runtime/TagHelpers/TagHelperScopeManager.cs

@@ -3,6 +3,8 @@
 
 using System;
 using System.Collections.Generic;
+using System.IO;
+using System.Threading.Tasks;
 
 namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
 {
@@ -25,10 +27,22 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
         /// Starts a <see cref="TagHelperExecutionContext"/> scope.
         /// </summary>
         /// <param name="tagName">The HTML tag name that the scope is associated with.</param>
+        /// <param name="uniqueId">An identifier unique to the HTML element this scope is for.</param>
+        /// <param name="executeChildContentAsync">A delegate used to execute the child content asynchronously.</param>
+        /// <param name="startWritingScope">A delegate used to start a writing scope in a Razor page.</param>
+        /// <param name="endWritingScope">A delegate used to end a writing scope in a Razor page.</param>
         /// <returns>A <see cref="TagHelperExecutionContext"/> to use.</returns>
-        public TagHelperExecutionContext Begin(string tagName)
+        public TagHelperExecutionContext Begin([NotNull] string tagName,
+                                               [NotNull] string uniqueId,
+                                               [NotNull] Func<Task> executeChildContentAsync,
+                                               [NotNull] Action startWritingScope,
+                                               [NotNull] Func<TextWriter> endWritingScope)
         {
-            var executionContext = new TagHelperExecutionContext(tagName);
+            var executionContext = new TagHelperExecutionContext(tagName,
+                                                                 uniqueId,
+                                                                 executeChildContentAsync,
+                                                                 startWritingScope,
+                                                                 endWritingScope);
 
             _executionScopes.Push(executionContext);
 

src/Microsoft.AspNet.Razor.Runtime/TagHelpers/TagHelperTypeResolver.cs

@@ -53,7 +53,7 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             IEnumerable<TypeInfo> libraryTypes;
             try
             {
-                libraryTypes = GetLibraryDefinedTypes(assemblyName);
+                libraryTypes = GetExportedTypes(assemblyName);
             }
             catch (Exception ex)
             {
@@ -72,8 +72,14 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             return validTagHelpers.Select(type => type.AsType());
         }
 
-        // Internal for testing, don't want to be loading assemblies during a test.
-        internal virtual IEnumerable<TypeInfo> GetLibraryDefinedTypes(AssemblyName assemblyName)
+        /// <summary>
+        /// Returns all exported types from the given <paramref name="assemblyName"/>
+        /// </summary>
+        /// <param name="assemblyName">The <see cref="AssemblyName"/> to get <see cref="TypeInfo"/>s from.</param>
+        /// <returns>
+        /// An <see cref="IEnumerable{TypeInfo}"/> of types exported from the given <paramref name="assemblyName"/>.
+        /// </returns>
+        protected virtual IEnumerable<TypeInfo> GetExportedTypes(AssemblyName assemblyName)
         {
             var assembly = Assembly.Load(assemblyName);
 

src/Microsoft.AspNet.Razor.Runtime/project.json

@@ -9,7 +9,8 @@
         "aspnet50": { },
         "aspnetcore50": {
             "dependencies": {
-                "System.Reflection.Extensions": "4.0.0-beta-*"
+                "System.Reflection.Extensions": "4.0.0-beta-*",
+                "System.Text.RegularExpressions": "4.0.10-beta-*"
             }
         }
     }

src/Microsoft.AspNet.Razor/Generator/CodeBuilderContext.cs

@@ -1,6 +1,8 @@
 // Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using Microsoft.AspNet.Razor.Parser;
+
 namespace Microsoft.AspNet.Razor.Generator
 {
     /// <summary>
@@ -12,9 +14,14 @@ namespace Microsoft.AspNet.Razor.Generator
         /// Instantiates a new instance of the <see cref="CodeBuilderContext"/> object.
         /// </summary>
         /// <param name="generatorContext">A <see cref="CodeGeneratorContext"/> to copy information from.</param>
-        public CodeBuilderContext(CodeGeneratorContext generatorContext)
+        /// <param name="errorSink">
+        /// The <see cref="ParserErrorSink"/> used to collect <see cref="Parser.SyntaxTree.RazorError"/>s encountered
+        /// when parsing the current Razor document.
+        /// </param>
+        public CodeBuilderContext(CodeGeneratorContext generatorContext, ParserErrorSink errorSink)
             : base(generatorContext)
         {
+            ErrorSink = errorSink;
             ExpressionRenderingMode = ExpressionRenderingMode.WriteToOutput;
         }
 
@@ -23,9 +30,11 @@ namespace Microsoft.AspNet.Razor.Generator
                                     string className,
                                     string rootNamespace,
                                     string sourceFile,
-                                    bool shouldGenerateLinePragmas)
+                                    bool shouldGenerateLinePragmas,
+                                    ParserErrorSink errorSink)
             : base(host, className, rootNamespace, sourceFile, shouldGenerateLinePragmas)
         {
+            ErrorSink = errorSink;
             ExpressionRenderingMode = ExpressionRenderingMode.WriteToOutput;
         }
 
@@ -56,5 +65,10 @@ namespace Microsoft.AspNet.Razor.Generator
         /// <see cref="CodeGeneratorContext.SourceFile"/>.
         /// </summary>
         public string Checksum { get; set; }
+
+        /// <summary>
+        /// Used to aggregate <see cref="Parser.SyntaxTree.RazorError"/>s.
+        /// </summary>
+        public ParserErrorSink ErrorSink { get; }
     }
 }

src/Microsoft.AspNet.Razor/Generator/Compiler/CodeBuilder/CSharp/CSharpCodeBuilder.cs

@@ -43,8 +43,6 @@ namespace Microsoft.AspNet.Razor.Generator.Compiler.CSharp
                 // Separate the usings and the class
                 writer.WriteLine();
 
-                new CSharpClassAttributeVisitor(writer, Context).Accept(Tree.Chunks);
-
                 using (BuildClassDeclaration(writer))
                 {
                     if (Host.DesignTimeMode)

src/Microsoft.AspNet.Razor/Generator/Compiler/CodeBuilder/CSharp/CSharpTagHelperCodeRenderer.cs

@@ -5,6 +5,7 @@ using System;
 using System.Collections.Generic;
 using System.Globalization;
 using System.Linq;
+using Microsoft.AspNet.Razor.Parser.SyntaxTree;
 using Microsoft.AspNet.Razor.TagHelpers;
 
 namespace Microsoft.AspNet.Razor.Generator.Compiler.CSharp
@@ -57,14 +58,7 @@ namespace Microsoft.AspNet.Razor.Generator.Compiler.CSharp
         {
             var tagHelperDescriptors = chunk.Descriptors;
 
-            // Find the first content behavior that doesn't have a content behavior of None.
-            // The resolver restricts content behavior collisions so the first one that's not None will be
-            // the content behavior we need to abide by. None can work in unison with other ContentBehaviors.
-            var contentBehavior = tagHelperDescriptors.Select(descriptor => descriptor.ContentBehavior)
-                                                      .FirstOrDefault(
-                                                            behavior => behavior != ContentBehavior.None);
-
-            RenderBeginTagHelperScope(chunk.TagName);
+            RenderBeginTagHelperScope(chunk.TagName, chunk.Children);
 
             RenderTagHelpersCreation(chunk);
 
@@ -77,42 +71,15 @@ namespace Microsoft.AspNet.Razor.Generator.Compiler.CSharp
 
             RenderUnboundHTMLAttributes(unboundHTMLAttributes);
 
-            switch (contentBehavior)
-            {
-                case ContentBehavior.None:
-                    RenderRunTagHelpers(bufferedBody: false);
-                    RenderTagOutput(_tagHelperContext.OutputGenerateStartTagMethodName);
-                    RenderTagHelperBody(chunk.Children, bufferBody: false);
-                    RenderTagOutput(_tagHelperContext.OutputGenerateEndTagMethodName);
-                    break;
-                case ContentBehavior.Append:
-                    RenderRunTagHelpers(bufferedBody: false);
-                    RenderTagOutput(_tagHelperContext.OutputGenerateStartTagMethodName);
-                    RenderTagHelperBody(chunk.Children, bufferBody: false);
-                    RenderTagOutput(_tagHelperContext.OutputGenerateContentMethodName);
-                    RenderTagOutput(_tagHelperContext.OutputGenerateEndTagMethodName);
-                    break;
-                case ContentBehavior.Prepend:
-                    RenderRunTagHelpers(bufferedBody: false);
-                    RenderTagOutput(_tagHelperContext.OutputGenerateStartTagMethodName);
-                    RenderTagOutput(_tagHelperContext.OutputGenerateContentMethodName);
-                    RenderTagHelperBody(chunk.Children, bufferBody: false);
-                    RenderTagOutput(_tagHelperContext.OutputGenerateEndTagMethodName);
-                    break;
-                case ContentBehavior.Replace:
-                    RenderRunTagHelpers(bufferedBody: false);
-                    RenderTagOutput(_tagHelperContext.OutputGenerateStartTagMethodName);
-                    RenderTagOutput(_tagHelperContext.OutputGenerateContentMethodName);
-                    RenderTagOutput(_tagHelperContext.OutputGenerateEndTagMethodName);
-                    break;
-                case ContentBehavior.Modify:
-                    RenderTagHelperBody(chunk.Children, bufferBody: true);
-                    RenderRunTagHelpers(bufferedBody: true);
-                    RenderTagOutput(_tagHelperContext.OutputGenerateStartTagMethodName);
-                    RenderTagOutput(_tagHelperContext.OutputGenerateContentMethodName);
-                    RenderTagOutput(_tagHelperContext.OutputGenerateEndTagMethodName);
-                    break;
-            }
+            RenderRunTagHelpers();
+
+            RenderTagOutput(_tagHelperContext.OutputGenerateStartTagMethodName);
+            RenderTagOutput(_tagHelperContext.OutputGeneratePreContentMethodName);
+
+            RenderTagHelperContent();
+
+            RenderTagOutput(_tagHelperContext.OutputGeneratePostContentMethodName);
+            RenderTagOutput(_tagHelperContext.OutputGenerateEndTagMethodName);
 
             RenderEndTagHelpersScope();
         }
@@ -122,11 +89,13 @@ namespace Microsoft.AspNet.Razor.Generator.Compiler.CSharp
             return "__" + descriptor.TypeName.Replace('.', '_');
         }
 
-        private void RenderBeginTagHelperScope(string tagName)
+        private void RenderBeginTagHelperScope(string tagName, IList<Chunk> children)
         {
             // Scopes/execution contexts are a runtime feature.
             if (_designTimeMode)
             {
+                // Render all of the tag helper children inline for IntelliSense.
+                _bodyVisitor.Accept(children);
                 return;
             }
 
@@ -135,10 +104,50 @@ namespace Microsoft.AspNet.Razor.Generator.Compiler.CSharp
             _writer.WriteStartAssignment(ExecutionContextVariableName)
                    .WriteStartInstanceMethodInvocation(ScopeManagerVariableName,
                                                        _tagHelperContext.ScopeManagerBeginMethodName);
+
+            // Assign a unique ID for this instance of the source HTML tag. This must be unique
+            // per call site, e.g. if the tag is on the view twice, there should be two IDs.
             _writer.WriteStringLiteral(tagName)
+                   .WriteParameterSeparator()
+                   .WriteStringLiteral(GenerateUniqueId())
+                   .WriteParameterSeparator();
+
+            // We remove the target writer so TagHelper authors can retrieve content.
+            var oldWriter = _context.TargetWriterName;
+            _context.TargetWriterName = null;
+
+            // Disabling instrumentation inside TagHelper bodies since we never know if it's accurate
+            var oldInstrumentation = _context.Host.EnableInstrumentation;
+            _context.Host.EnableInstrumentation = false;
+
+            using (_writer.BuildAsyncLambda(endLine: false))
+            {
+                // Render all of the tag helper children.
+                _bodyVisitor.Accept(children);
+            }
+
+            _context.Host.EnableInstrumentation = oldInstrumentation;
+
+            _context.TargetWriterName = oldWriter;
+
+            _writer.WriteParameterSeparator()
+                   .Write(_tagHelperContext.StartWritingScopeMethodName)
+                   .WriteParameterSeparator()
+                   .Write(_tagHelperContext.EndWritingScopeMethodName)
                    .WriteEndMethodInvocation();
         }
 
+        /// <summary>
+        /// Generates a unique ID for an HTML element.
+        /// </summary>
+        /// <returns>
+        /// A globally unique ID.
+        /// </returns>
+        protected virtual string GenerateUniqueId()
+        {
+            return Guid.NewGuid().ToString("N");
+        }
+
         private void RenderTagHelpersCreation(TagHelperChunk chunk)
         {
             var tagHelperDescriptors = chunk.Descriptors;
@@ -213,48 +222,67 @@ namespace Microsoft.AspNet.Razor.Generator.Compiler.CSharp
                                                       tagHelperVariableName,
                                                       attributeDescriptor.PropertyName);
 
-                    _writer.WriteStartAssignment(valueAccessor);
-
                     // If we haven't recorded this attribute value before then we need to record its value.
                     if (!attributeValueRecorded)
                     {
                         // We only need to create attribute values once per HTML element (not once per tag helper).
-                        // We're saving the value accessor so we can retrieve it later if there are more tag helpers that
-                        // need the value.
+                        // We're saving the value accessor so we can retrieve it later if there are more tag
+                        // helpers that need the value.
                         htmlAttributeValues.Add(attributeDescriptor.Name, valueAccessor);
 
                         if (bufferableAttribute)
                         {
-                            // If the attribute is bufferable but has a plain text value that means the value
-                            // is a string which needs to be surrounded in quotes.
+                            _writer.WriteStartAssignment(valueAccessor);
+
                             if (isPlainTextValue)
                             {
+                                // If the attribute is bufferable but has a plain text value that means the value
+                                // is a string which needs to be surrounded in quotes.
                                 RenderQuotedAttributeValue(textValue, attributeDescriptor);
                             }
                             else
                             {
-                                // The value contains more than plain text. e.g. someAttribute="Time: @DateTime.Now"
+                                // The value contains more than plain text e.g.
+                                // stringAttribute ="Time: @DateTime.Now"
                                 RenderBufferedAttributeValue(attributeDescriptor);
                             }
+
+                            _writer.WriteLine(";");
                         }
                         else
                         {
-                            // TODO: Make complex types in non-bufferable attributes work in
-                            // https://github.com/aspnet/Razor/issues/129
-                            if (!isPlainTextValue)
+                            // Write out simple assignment for non-string property value. Try to keep the whole
+                            // statement together and the #line pragma correct to make debugging possible.
+                            using (var lineMapper = new CSharpLineMappingWriter(
+                                _writer,
+                                attributeValueChunk.Association.Start,
+                                _context.SourceFile))
                             {
+                                // Place the assignment LHS to align RHS with original attribute value's indentation.
+                                // Unfortunately originalIndent is incorrect if original line contains tabs. Unable to
+                                // use a CSharpPaddingBuilder because the Association has no Previous node; lost the
+                                // original Span sequence when the parse tree was rewritten.
+                                var originalIndent = attributeValueChunk.Start.CharacterIndex;
+                                var generatedLength = valueAccessor.Length + " = ".Length;
+                                var newIndent = originalIndent - generatedLength;
+                                if (newIndent > 0)
+                                {
+                                    _writer.Indent(newIndent);
+                                }
+
+                                _writer.WriteStartAssignment(valueAccessor);
+                                lineMapper.MarkLineMappingStart();
+
+                                // Write out bare expression for this attribute value. Property is not a string.
+                                // So quoting or buffering are not helpful.
+                                RenderRawAttributeValue(attributeValueChunk, attributeDescriptor, isPlainTextValue);
+
+                                // End the assignment to the attribute.
+                                lineMapper.MarkLineMappingEnd();
                                 _writer.WriteLine(";");
-                                return;
                             }
-
-                            // We aren't a bufferable attribute which means we have no Razor code in our value.
-                            // Therefore we can just use the "textValue" as the attribute value.
-                            RenderRawAttributeValue(textValue, attributeDescriptor);
                         }
 
-                        // End the assignment to the attribute.
-                        _writer.WriteLine(";");
-
                         // Execution contexts are a runtime feature.
                         if (_designTimeMode)
                         {
@@ -262,20 +290,23 @@ namespace Microsoft.AspNet.Razor.Generator.Compiler.CSharp
                         }
 
                         // We need to inform the context of the attribute value.
-                        _writer.WriteStartInstanceMethodInvocation(
-                            ExecutionContextVariableName,
-                            _tagHelperContext.ExecutionContextAddTagHelperAttributeMethodName);
-
-                        _writer.WriteStringLiteral(attributeDescriptor.Name)
-                               .WriteParameterSeparator()
-                               .Write(valueAccessor)
-                               .WriteEndMethodInvocation();
+                        _writer
+                            .WriteStartInstanceMethodInvocation(
+                                ExecutionContextVariableName,
+                                _tagHelperContext.ExecutionContextAddTagHelperAttributeMethodName)
+                            .WriteStringLiteral(attributeDescriptor.Name)
+                            .WriteParameterSeparator()
+                            .Write(valueAccessor)
+                            .WriteEndMethodInvocation();
                     }
                     else
                     {
-                        // The attribute value has already been recorded, lets retrieve it from the stored value accessors.
-                        _writer.Write(htmlAttributeValues[attributeDescriptor.Name])
-                               .WriteLine(";");
+                        // The attribute value has already been recorded, lets retrieve it from the stored value
+                        // accessors.
+                        _writer
+                            .WriteStartAssignment(valueAccessor)
+                            .Write(htmlAttributeValues[attributeDescriptor.Name])
+                            .WriteLine(";");
                     }
                 }
             }
@@ -323,18 +354,74 @@ namespace Microsoft.AspNet.Razor.Generator.Compiler.CSharp
             }
         }
 
-        private void RenderTagHelperBody(IList<Chunk> children, bool bufferBody)
+        private void RenderTagHelperContent()
         {
-            // If we want to buffer the body we need to create a writing scope to capture the body content.
-            if (bufferBody)
+            // Rendering output is a runtime feature.
+            if (_designTimeMode)
             {
-                // Render all of the tag helper children in a buffered writing scope.
-                BuildBufferedWritingScope(children);
+                return;
             }
-            else
+
+            _writer.Write("if (")
+                   .Write(ExecutionContextVariableName)
+                   .Write(".")
+                   .Write(_tagHelperContext.ExecutionContextOutputPropertyName)
+                   .Write(".")
+                   .Write(_tagHelperContext.OutputContentSetPropertyName)
+                   .WriteLine(")");
+
+            // At this point in the codegen, TagHelperOutput.Content is set. We need to use this to render the Content 
+            // instead of executing the child content
+            using (_writer.BuildScope())
             {
-                // Render all of the tag helper children.
-                _bodyVisitor.Accept(children);
+                RenderTagOutput(_tagHelperContext.OutputGenerateContentMethodName);
+            }
+
+            _writer.Write("else if (")
+                   .Write(ExecutionContextVariableName)
+                   .Write(".")
+                   .Write(_tagHelperContext.ExecutionContextChildContentRetrievedPropertyName)
+                   .WriteLine(")");
+
+            // Render the body of the else if statement, at this point in the codegen the GetChildContentAsync method 
+            // was invoked but the TagHelperOutput's Content was not set. Call into GetChildContentAsync to retrieve
+            // the cached value of the content so we don't execute the child content twice.
+            using (_writer.BuildScope())
+            {
+                CSharpCodeVisitor.RenderPreWriteStart(_writer, _context);
+
+                _writer.WriteInstanceMethodInvocation(ExecutionContextVariableName,
+                                                      _tagHelperContext.ExecutionContextGetChildContentAsyncMethodName,
+                                                      endLine: false);
+
+                _writer.Write(".Result")
+                       .WriteEndMethodInvocation();
+            }
+
+            _writer.WriteLine("else");
+
+            // Render the body of the else statement, at this point in the codegen the GetChildContentAsync method 
+            // was not invoked and the TagHelperOutput's Content was not set. Call into ExecuteChildContentAsync to
+            // to execute and render child content.
+            using (_writer.BuildScope())
+            {
+                if (!string.IsNullOrEmpty(_context.TargetWriterName))
+                {
+                    _writer.WriteMethodInvocation(
+                        _tagHelperContext.StartWritingScopeMethodName,
+                        _context.TargetWriterName);
+                }
+
+                _writer.WriteInstanceMethodInvocation(
+                    ExecutionContextVariableName,
+                    _tagHelperContext.ExecutionContextExecuteChildContentAsyncMethodName,
+                    endLine: false);
+                _writer.WriteLine(".Wait();");
+
+                if (!string.IsNullOrEmpty(_context.TargetWriterName))
+                {
+                    _writer.WriteMethodInvocation(_tagHelperContext.EndWritingScopeMethodName);
+                }
             }
         }
 
@@ -369,7 +456,7 @@ namespace Microsoft.AspNet.Razor.Generator.Compiler.CSharp
                    .WriteEndMethodInvocation();
         }
 
-        private void RenderRunTagHelpers(bool bufferedBody)
+        private void RenderRunTagHelpers()
         {
             // No need to run anything in design time mode.
             if (_designTimeMode)
@@ -383,36 +470,38 @@ namespace Microsoft.AspNet.Razor.Generator.Compiler.CSharp
                    .Write(" = ")
                    .WriteStartInstanceMethodInvocation(RunnerVariableName,
                                                        _tagHelperContext.RunnerRunAsyncMethodName);
-            _writer.Write(ExecutionContextVariableName);
 
-            if (bufferedBody)
-            {
-                _writer.WriteParameterSeparator()
-                       .Write(StringValueBufferVariableName);
-            }
-
-            _writer.WriteEndMethodInvocation(endLine: false)
+            _writer.Write(ExecutionContextVariableName)
+                   .WriteEndMethodInvocation(endLine: false)
                    .WriteLine(".Result;");
         }
 
         private void RenderBufferedAttributeValue(TagHelperAttributeDescriptor attributeDescriptor)
         {
+            // Pass complexValue: false because variable.ToString() replaces any original complexity in the expression.
             RenderAttributeValue(
                 attributeDescriptor,
                 valueRenderer: (writer) =>
                 {
                     RenderBufferedAttributeValueAccessor(writer);
-                });
+                },
+                complexValue: false);
         }
 
-        private void RenderRawAttributeValue(string value, TagHelperAttributeDescriptor attributeDescriptor)
+        private void RenderRawAttributeValue(
+            Chunk attributeValueChunk,
+            TagHelperAttributeDescriptor attributeDescriptor,
+            bool isPlainTextValue)
         {
             RenderAttributeValue(
                 attributeDescriptor,
                 valueRenderer: (writer) =>
                 {
-                    writer.Write(value);
-                });
+                    var visitor =
+                        new CSharpTagHelperAttributeValueVisitor(writer, _context, attributeDescriptor.TypeName);
+                    visitor.Accept(attributeValueChunk);
+                },
+                complexValue: !isPlainTextValue);
         }
 
         private void RenderQuotedAttributeValue(string value, TagHelperAttributeDescriptor attributeDescriptor)
@@ -422,7 +511,8 @@ namespace Microsoft.AspNet.Razor.Generator.Compiler.CSharp
                 valueRenderer: (writer) =>
                 {
                     writer.WriteStringLiteral(value);
-                });
+                },
+                complexValue: false);
         }
 
         private void BuildBufferedWritingScope(Chunk htmlAttributeChunk)
@@ -473,9 +563,15 @@ namespace Microsoft.AspNet.Razor.Generator.Compiler.CSharp
         }
 
         private void RenderAttributeValue(TagHelperAttributeDescriptor attributeDescriptor,
-                                          Action<CSharpCodeWriter> valueRenderer)
+                                          Action<CSharpCodeWriter> valueRenderer,
+                                          bool complexValue)
         {
-            AttributeValueCodeRenderer.RenderAttributeValue(attributeDescriptor, _writer, _context, valueRenderer);
+            AttributeValueCodeRenderer.RenderAttributeValue(
+                attributeDescriptor,
+                _writer,
+                _context,
+                valueRenderer,
+                complexValue);
         }
 
         private void RenderBufferedAttributeValueAccessor(CSharpCodeWriter writer)

src/Microsoft.AspNet.Razor/Generator/Compiler/CodeBuilder/CSharp/Visitors/CSharpClassAttributeVisitor.cs

@@ -1,25 +0,0 @@
-// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
-// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
-
-using Microsoft.AspNet.Razor.Parser;
-
-namespace Microsoft.AspNet.Razor.Generator.Compiler.CSharp
-{
-    public class CSharpClassAttributeVisitor : CodeVisitor<CSharpCodeWriter>
-    {
-        public CSharpClassAttributeVisitor(CSharpCodeWriter writer, CodeBuilderContext context)
-            : base(writer, context)
-        { }
-
-        protected override void Visit(SessionStateChunk chunk)
-        {
-            Writer.Write("[")
-                  .Write(typeof(RazorDirectiveAttribute).FullName)
-                  .Write("(")
-                  .WriteStringLiteral(SyntaxConstants.CSharp.SessionStateKeyword)
-                  .WriteParameterSeparator()
-                  .WriteStringLiteral(chunk.Value)
-                  .WriteLine(")]");
-        }
-    }
-}

src/Microsoft.AspNet.Razor/Generator/Compiler/CodeBuilder/CSharp/Visitors/CSharpTagHelperAttributeValueVisitor.cs

@@ -0,0 +1,179 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.AspNet.Razor.Parser;
+using Microsoft.AspNet.Razor.Parser.SyntaxTree;
+
+namespace Microsoft.AspNet.Razor.Generator.Compiler.CSharp
+{
+    /// <summary>
+    /// <see cref="CodeVisitor{CSharpCodeWriter}"/> that writes code for a non-<see langword="string"/> tag helper
+    /// bound attribute value.
+    /// </summary>
+    /// <remarks>
+    /// Since attribute value is not written out as HTML, does not emit instrumentation. Further this
+    /// <see cref="CodeVisitor{CSharpCodeWriter}"/> writes identical code at design- and runtime.
+    /// </remarks>
+    public class CSharpTagHelperAttributeValueVisitor : CodeVisitor<CSharpCodeWriter>
+    {
+        private string _attributeTypeName;
+        private bool _firstChild;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="CSharpTagHelperAttributeValueVisitor"/> class.
+        /// </summary>
+        /// <param name="writer">The <see cref="CSharpCodeWriter"/> used to write code.</param>
+        /// <param name="context">
+        /// A <see cref="CodeBuilderContext"/> instance that contains information about the current code generation
+        /// process.
+        /// </param>
+        /// <param name="attributeTypeName">
+        /// Full name of the property <see cref="System.Type"/> for which this
+        /// <see cref="CSharpTagHelperAttributeValueVisitor"/> is writing the value.
+        /// </param>
+        public CSharpTagHelperAttributeValueVisitor(
+            CSharpCodeWriter writer,
+            CodeBuilderContext context,
+            string attributeTypeName)
+            : base(writer, context)
+        {
+            _attributeTypeName = attributeTypeName;
+        }
+
+        /// <summary>
+        /// Writes code for the given <paramref name="chunk"/>.
+        /// </summary>
+        /// <param name="chunk">The <see cref="ChunkBlock"/> to render.</param>
+        /// <remarks>
+        /// Tracks code mappings for all children while writing.
+        /// </remarks>
+        protected override void Visit(ChunkBlock chunk)
+        {
+            // Line mappings are captured in RenderCode(), not this method.
+            _firstChild = true;
+            Accept(chunk.Children);
+
+            if (_firstChild)
+            {
+                // Attribute value was empty.
+                Context.ErrorSink.OnError(
+                    chunk.Association.Start,
+                    RazorResources.TagHelpers_AttributeExpressionRequired,
+                    chunk.Association.Length);
+            }
+        }
+
+        /// <summary>
+        /// Writes code for the given <paramref name="chunk"/>.
+        /// </summary>
+        /// <param name="chunk">The <see cref="ExpressionBlockChunk"/> to render.</param>
+        protected override void Visit(ExpressionBlockChunk chunk)
+        {
+            Accept(chunk.Children);
+        }
+
+        /// <summary>
+        /// Writes code for the given <paramref name="chunk"/>.
+        /// </summary>
+        /// <param name="chunk">The <see cref="ExpressionChunk"/> to render.</param>
+        protected override void Visit(ExpressionChunk chunk)
+        {
+            RenderCode(chunk.Code, (Span)chunk.Association);
+        }
+
+        /// <summary>
+        /// Writes code for the given <paramref name="chunk"/>.
+        /// </summary>
+        /// <param name="chunk">The <see cref="LiteralChunk"/> to render.</param>
+        protected override void Visit(LiteralChunk chunk)
+        {
+            RenderCode(chunk.Text, (Span)chunk.Association);
+        }
+
+        /// <summary>
+        /// Writes code for the given <paramref name="chunk"/>.
+        /// </summary>
+        /// <param name="chunk">The <see cref="ResolveUrlChunk"/> to render.</param>
+        /// <remarks>
+        /// Allowed to support future C# extensions. Likely "~/..." will lead to a C# compilation error but that is up
+        /// to the compiler.
+        /// </remarks>
+        protected override void Visit(ResolveUrlChunk chunk)
+        {
+            RenderCode(chunk.Url, (Span)chunk.Association);
+        }
+
+        /// <summary>
+        /// Writes code for the given <paramref name="chunk"/>.
+        /// </summary>
+        /// <param name="chunk">The <see cref="SectionChunk"/> to render.</param>
+        /// <remarks>
+        /// Unconditionally adds a <see cref="RazorError"/> to inform user of unexpected <c>@section</c> directive.
+        /// </remarks>
+        protected override void Visit(SectionChunk chunk)
+        {
+            Context.ErrorSink.OnError(
+                chunk.Association.Start,
+                RazorResources.FormatTagHelpers_Directives_NotSupported_InAttributes(
+                    SyntaxConstants.CSharp.SectionKeyword),
+                chunk.Association.Length);
+        }
+
+        /// <summary>
+        /// Writes code for the given <paramref name="chunk"/>.
+        /// </summary>
+        /// <param name="chunk">The <see cref="SetLayoutChunk"/> to render.</param>
+        /// <remarks>
+        /// Unconditionally adds a <see cref="RazorError"/> to inform user of unexpected <c>@layout</c> directive.
+        /// </remarks>
+        protected override void Visit(SetLayoutChunk chunk)
+        {
+            Context.ErrorSink.OnError(
+                chunk.Association.Start,
+                RazorResources.FormatTagHelpers_Directives_NotSupported_InAttributes(
+                    SyntaxConstants.CSharp.LayoutKeyword),
+                chunk.Association.Length);
+        }
+
+        /// <summary>
+        /// Writes code for the given <paramref name="chunk"/>.
+        /// </summary>
+        /// <param name="chunk">The <see cref="StatementChunk"/> to render.</param>
+        /// <remarks>
+        /// Unconditionally adds a <see cref="RazorError"/> to inform user of unexpected code block.
+        /// </remarks>
+        protected override void Visit(StatementChunk chunk)
+        {
+            Context.ErrorSink.OnError(
+                chunk.Association.Start,
+                RazorResources.TagHelpers_CodeBlocks_NotSupported_InAttributes,
+                chunk.Association.Length);
+        }
+
+        /// <summary>
+        /// Writes code for the given <paramref name="chunk"/>.
+        /// </summary>
+        /// <param name="chunk">The <see cref="TemplateChunk"/> to render.</param>
+        /// <remarks>
+        /// Unconditionally adds a <see cref="RazorError"/> to inform user of unexpected template e.g.
+        /// <c>@&lt;p&gt;paragraph@&lt;/p&gt;</c>.
+        /// </remarks>
+        protected override void Visit(TemplateChunk chunk)
+        {
+            Context.ErrorSink.OnError(
+                chunk.Association.Start,
+                RazorResources.FormatTagHelpers_InlineMarkupBlocks_NotSupported_InAttributes(_attributeTypeName),
+                chunk.Association.Length);
+        }
+
+        // Tracks the code mapping and writes code for a leaf node in the attribute value Chunk tree.
+        private void RenderCode(string code, Span association)
+        {
+            _firstChild = false;
+            using (new CSharpLineMappingWriter(Writer, association.Start, code.Length))
+            {
+                Writer.Write(code);
+            }
+        }
+    }
+}

src/Microsoft.AspNet.Razor/Generator/Compiler/CodeBuilder/CSharp/Visitors/CSharpTagHelperFieldDeclarationVisitor.cs

@@ -34,9 +34,13 @@ namespace Microsoft.AspNet.Razor.Generator.Compiler.CSharp
                 // Runtime fields aren't useful during design time.
                 if (!Context.Host.DesignTimeMode)
                 {
+                    // Need to disable the warning "X is assigned to but never used." for the value buffer since
+                    // whether it's used depends on how a TagHelper is used.
+                    Writer.WritePragma("warning disable 0414");
                     WritePrivateField(typeof(TextWriter).FullName,
                                       CSharpTagHelperCodeRenderer.StringValueBufferVariableName,
                                       value: null);
+                    Writer.WritePragma("warning restore 0414");
 
                     WritePrivateField(_tagHelperContext.ExecutionContextTypeName,
                                       CSharpTagHelperCodeRenderer.ExecutionContextVariableName,

src/Microsoft.AspNet.Razor/Generator/Compiler/CodeBuilder/ChunkVisitor.cs

@@ -113,10 +113,6 @@ namespace Microsoft.AspNet.Razor.Generator.Compiler
             {
                 Visit((ChunkBlock)chunk);
             }
-            else if (chunk is SessionStateChunk)
-            {
-                Visit((SessionStateChunk)chunk);
-            }
         }
 
         protected abstract void Visit(LiteralChunk chunk);
@@ -138,6 +134,5 @@ namespace Microsoft.AspNet.Razor.Generator.Compiler
         protected abstract void Visit(TemplateChunk chunk);
         protected abstract void Visit(SetLayoutChunk chunk);
         protected abstract void Visit(ExpressionBlockChunk chunk);
-        protected abstract void Visit(SessionStateChunk chunk);
     }
 }

src/Microsoft.AspNet.Razor/Generator/Compiler/CodeBuilder/CodeVisitor.cs

@@ -66,8 +66,5 @@ namespace Microsoft.AspNet.Razor.Generator.Compiler
         protected override void Visit(SetLayoutChunk chunk)
         {
         }
-        protected override void Visit(SessionStateChunk chunk)
-        {
-        }
     }
 }

src/Microsoft.AspNet.Razor/Generator/Compiler/CodeTree/Chunks/SessionStateChunk.cs

@@ -1,10 +0,0 @@
-// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
-// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
-
-namespace Microsoft.AspNet.Razor.Generator.Compiler
-{
-    public class SessionStateChunk : Chunk
-    {
-        public string Value { get; set; }
-    }
-}

src/Microsoft.AspNet.Razor/Generator/Compiler/CodeTree/CodeTreeBuilder.cs

@@ -145,14 +145,6 @@ namespace Microsoft.AspNet.Razor.Generator.Compiler
             }, association, topLevel: true);
         }
 
-        public void AddSessionStateChunk(string value, SyntaxTreeNode association)
-        {
-            AddChunk(new SessionStateChunk
-            {
-                Value = value
-            }, association, topLevel: true);
-        }
-
         public T StartChunkBlock<T>(SyntaxTreeNode association) where T : ChunkBlock, new()
         {
             return StartChunkBlock<T>(association, topLevel: false);

src/Microsoft.AspNet.Razor/Generator/Compiler/LineMappings/LineMapping.cs

@@ -1,6 +1,8 @@
 // Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System.Globalization;
+
 namespace Microsoft.AspNet.Razor.Generator.Compiler
 {
     public class LineMapping
@@ -40,5 +42,10 @@ namespace Microsoft.AspNet.Razor.Generator.Compiler
         {
             return !left.Equals(right);
         }
+
+        public override string ToString()
+        {
+            return string.Format(CultureInfo.CurrentUICulture, "{0} -> {1}", DocumentLocation, GeneratedLocation);
+        }
     }
 }

src/Microsoft.AspNet.Razor/Generator/Compiler/LineMappings/MappingLocation.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System.Globalization;
 using Microsoft.AspNet.Razor.Text;
 
 namespace Microsoft.AspNet.Razor.Generator.Compiler
@@ -37,6 +38,16 @@ namespace Microsoft.AspNet.Razor.Generator.Compiler
             return base.GetHashCode();
         }
 
+        public override string ToString()
+        {
+            return string.Format(
+                CultureInfo.CurrentCulture, "({0}:{1},{2} [{3}])",
+                AbsoluteIndex,
+                LineIndex,
+                CharacterIndex,
+                ContentLength);
+        }
+
         public static bool operator ==(MappingLocation left, MappingLocation right)
         {
             return left.Equals(right);

src/Microsoft.AspNet.Razor/Generator/GeneratedTagHelperContext.cs

@@ -17,9 +17,15 @@ namespace Microsoft.AspNet.Razor.Generator
             RunnerRunAsyncMethodName = "RunAsync";
             ScopeManagerBeginMethodName = "Begin";
             ScopeManagerEndMethodName = "End";
+            OutputContentSetPropertyName = "ContentSet";
             OutputGenerateStartTagMethodName = "GenerateStartTag";
+            OutputGeneratePreContentMethodName = "GeneratePreContent";
             OutputGenerateContentMethodName = "GenerateContent";
+            OutputGeneratePostContentMethodName = "GeneratePostContent";
             OutputGenerateEndTagMethodName = "GenerateEndTag";
+            ExecutionContextChildContentRetrievedPropertyName = "ChildContentRetrieved";
+            ExecutionContextExecuteChildContentAsyncMethodName = "ExecuteChildContentAsync";
+            ExecutionContextGetChildContentAsyncMethodName = "GetChildContentAsync";
             ExecutionContextAddMethodName = "Add";
             ExecutionContextAddTagHelperAttributeMethodName = "AddTagHelperAttribute";
             ExecutionContextAddHtmlAttributeMethodName = "AddHtmlAttribute";
@@ -51,21 +57,52 @@ namespace Microsoft.AspNet.Razor.Generator
         /// </summary>
         public string ScopeManagerEndMethodName { get; set; }
 
+        /// <summary>
+        /// The name of the property used to determine if a tag helper output's content was set.
+        /// </summary>
+        public string OutputContentSetPropertyName { get; set; }
+
         /// <summary>
         /// The name of the method used to generate a tag helper output's start tag.
         /// </summary>
         public string OutputGenerateStartTagMethodName { get; set; }
 
+        /// <summary>
+        /// The name of the method used to generate a tag helper output's pre content.
+        /// </summary>
+        public string OutputGeneratePreContentMethodName { get; set; }
+
         /// <summary>
         /// The name of the method used to generate a tag helper output's content.
         /// </summary>
         public string OutputGenerateContentMethodName { get; set; }
 
+        /// <summary>
+        /// The name of the method used to generate a tag helper output's post-content.
+        /// </summary>
+        public string OutputGeneratePostContentMethodName { get; set; }
+
         /// <summary>
         /// The name of the method used to generate a tag helper output's end tag.
         /// </summary>
         public string OutputGenerateEndTagMethodName { get; set; }
 
+        /// <summary>
+        /// The name of the <see cref="ExecutionContextTypeName"/> method used to get a 
+        /// <see cref="System.Threading.Tasks.Task"/> that executes tag helper child content.
+        /// </summary>
+        public string ExecutionContextChildContentRetrievedPropertyName { get; set; }
+
+        /// <summary>
+        /// </summary>
+        public string ExecutionContextExecuteChildContentAsyncMethodName { get; set; }
+
+        /// <summary>
+        /// The name of the <see cref="ExecutionContextTypeName"/> method used to execute and retrieve tag helper 
+        /// child content.
+        /// </summary>
+        public string ExecutionContextGetChildContentAsyncMethodName { get; set; }
+
         /// <summary>
         /// The name of the <see cref="ExecutionContextTypeName"/> method used to add tag helper attributes.
         /// </summary>

src/Microsoft.AspNet.Razor/Generator/RazorDirectiveAttributeCodeGenerator.cs

@@ -1,53 +0,0 @@
-// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
-// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
-
-using System;
-using Microsoft.AspNet.Razor.Parser;
-using Microsoft.AspNet.Razor.Parser.SyntaxTree;
-
-namespace Microsoft.AspNet.Razor.Generator
-{
-    public class RazorDirectiveAttributeCodeGenerator : SpanCodeGenerator
-    {
-        public RazorDirectiveAttributeCodeGenerator(string name, string value)
-        {
-            if (String.IsNullOrEmpty(name))
-            {
-                throw new ArgumentException(CommonResources.Argument_Cannot_Be_Null_Or_Empty, "name");
-            }
-            Name = name;
-            Value = value ?? String.Empty; // Coerce to empty string if it was null.
-        }
-
-        public string Name { get; private set; }
-
-        public string Value { get; private set; }
-
-        public override void GenerateCode(Span target, CodeGeneratorContext context)
-        {
-            if (Name == SyntaxConstants.CSharp.SessionStateKeyword)
-            {
-                context.CodeTreeBuilder.AddSessionStateChunk(Value, target);
-            }
-        }
-
-        public override string ToString()
-        {
-            return "Directive: " + Name + ", Value: " + Value;
-        }
-
-        public override bool Equals(object obj)
-        {
-            var other = obj as RazorDirectiveAttributeCodeGenerator;
-            return other != null &&
-                   Name.Equals(other.Name, StringComparison.OrdinalIgnoreCase) &&
-                   Value.Equals(other.Value, StringComparison.OrdinalIgnoreCase);
-        }
-
-        public override int GetHashCode()
-        {
-            return Tuple.Create(Name.ToUpperInvariant(), Value.ToUpperInvariant())
-                .GetHashCode();
-        }
-    }
-}

src/Microsoft.AspNet.Razor/Generator/TagHelperCodeGenerator.cs

@@ -3,10 +3,12 @@
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using Microsoft.AspNet.Razor.Generator.Compiler;
 using Microsoft.AspNet.Razor.Parser.SyntaxTree;
 using Microsoft.AspNet.Razor.Parser.TagHelpers;
 using Microsoft.AspNet.Razor.TagHelpers;
+using Microsoft.AspNet.Razor.Text;
 
 namespace Microsoft.AspNet.Razor.Generator
 {
@@ -60,10 +62,13 @@ namespace Microsoft.AspNet.Razor.Generator
                 attribute.Value.Accept(codeGenerator);
 
                 var chunks = codeGenerator.Context.CodeTreeBuilder.CodeTree.Chunks;
+                var first = chunks.FirstOrDefault();
 
                 attributes[attribute.Key] = new ChunkBlock
                 {
-                    Children = chunks
+                    Association = first?.Association,
+                    Children = chunks,
+                    Start = first == null ? SourceLocation.Zero : first.Start
                 };
 
                 // Reset the code tree builder so we can build a new one for the next attribute

src/Microsoft.AspNet.Razor/GeneratorResults.cs

@@ -3,6 +3,7 @@
 
 using System.Collections.Generic;
 using Microsoft.AspNet.Razor.Generator.Compiler;
+using Microsoft.AspNet.Razor.Parser;
 using Microsoft.AspNet.Razor.Parser.SyntaxTree;
 using Microsoft.AspNet.Razor.TagHelpers;
 
@@ -24,7 +25,7 @@ namespace Microsoft.AspNet.Razor
                                 [NotNull] CodeTree codeTree)
             : this(parserResults.Document,
                    parserResults.TagHelperDescriptors,
-                   parserResults.ParserErrors,
+                   parserResults.ErrorSink,
                    codeBuilderResult,
                    codeTree)
         {
@@ -34,35 +35,21 @@ namespace Microsoft.AspNet.Razor
         /// Instantiates a new <see cref="GeneratorResults"/> instance.
         /// </summary>
         /// <param name="document">The <see cref="Block"/> for the syntax tree.</param>
-        /// <param name="tagHelperDescriptors"><see cref="TagHelperDescriptor"/>s for the document.</param>
-        /// <param name="parserErrors"><see cref="RazorError"/>s encountered when parsing the document.</param>
+        /// <param name="tagHelperDescriptors">
+        /// The <see cref="TagHelperDescriptor"/>s that apply to the current Razor document.
+        /// </param>
+        /// <param name="errorSink">
+        /// The <see cref="ParserErrorSink"/> used to collect <see cref="RazorError"/>s encountered when parsing the
+        /// current Razor document.
+        /// </param>
         /// <param name="codeBuilderResult">The results of generating code for the document.</param>
         /// <param name="codeTree">A <see cref="CodeTree"/> for the document.</param>
         public GeneratorResults([NotNull] Block document,
                                 [NotNull] IEnumerable<TagHelperDescriptor> tagHelperDescriptors,
-                                [NotNull] IList<RazorError> parserErrors,
+                                [NotNull] ParserErrorSink errorSink,
                                 [NotNull] CodeBuilderResult codeBuilderResult,
                                 [NotNull] CodeTree codeTree)
-            : this(parserErrors.Count == 0, document, tagHelperDescriptors, parserErrors, codeBuilderResult, codeTree)
-        {
-        }
-
-        /// <summary>
-        /// Instantiates a new <see cref="GeneratorResults"/> instance.
-        /// </summary>
-        /// <param name="success"><c>true</c> if parsing was successful, <c>false</c> otherwise.</param>
-        /// <param name="document">The <see cref="Block"/> for the syntax tree.</param>
-        /// <param name="tagHelperDescriptors"><see cref="TagHelperDescriptor"/>s for the document.</param>
-        /// <param name="parserErrors"><see cref="RazorError"/>s encountered when parsing the document.</param>
-        /// <param name="codeBuilderResult">The results of generating code for the document.</param>
-        /// <param name="codeTree">A <see cref="CodeTree"/> for the document.</param>
-        protected GeneratorResults(bool success,
-                                   [NotNull] Block document,
-                                   [NotNull] IEnumerable<TagHelperDescriptor> tagHelperDescriptors,
-                                   [NotNull] IList<RazorError> parserErrors,
-                                   [NotNull] CodeBuilderResult codeBuilderResult,
-                                   [NotNull] CodeTree codeTree)
-            : base(success, document, tagHelperDescriptors, parserErrors)
+            : base(document, tagHelperDescriptors, errorSink)
         {
             GeneratedCode = codeBuilderResult.Code;
             DesignTimeLineMappings = codeBuilderResult.DesignTimeLineMappings;

src/Microsoft.AspNet.Razor/Parser/CSharpCodeParser.Directives.cs

@@ -25,7 +25,6 @@ namespace Microsoft.AspNet.Razor.Parser
             MapDirectives(SectionDirective, SyntaxConstants.CSharp.SectionKeyword);
             MapDirectives(HelperDirective, SyntaxConstants.CSharp.HelperKeyword);
             MapDirectives(LayoutDirective, SyntaxConstants.CSharp.LayoutKeyword);
-            MapDirectives(SessionStateDirective, SyntaxConstants.CSharp.SessionStateKeyword);
         }
 
         protected virtual void AddTagHelperDirective()
@@ -58,65 +57,6 @@ namespace Microsoft.AspNet.Razor.Parser
             Output(SpanKind.MetaCode, foundNewline ? AcceptedCharacters.None : AcceptedCharacters.Any);
         }
 
-        protected virtual void SessionStateDirective()
-        {
-            AssertDirective(SyntaxConstants.CSharp.SessionStateKeyword);
-            AcceptAndMoveNext();
-
-            SessionStateDirectiveCore();
-        }
-
-        protected void SessionStateDirectiveCore()
-        {
-            SessionStateTypeDirective(RazorResources.ParserEror_SessionDirectiveMissingValue, (key, value) => new RazorDirectiveAttributeCodeGenerator(key, value));
-        }
-
-        protected void SessionStateTypeDirective(string noValueError, Func<string, string, SpanCodeGenerator> createCodeGenerator)
-        {
-            // Set the block type
-            Context.CurrentBlock.Type = BlockType.Directive;
-
-            // Accept whitespace
-            var remainingWs = AcceptSingleWhiteSpaceCharacter();
-
-            if (Span.Symbols.Count > 1)
-            {
-                Span.EditHandler.AcceptedCharacters = AcceptedCharacters.None;
-            }
-
-            Output(SpanKind.MetaCode);
-
-            if (remainingWs != null)
-            {
-                Accept(remainingWs);
-            }
-            AcceptWhile(IsSpacingToken(includeNewLines: false, includeComments: true));
-
-            // Parse a Type Name
-            if (!ValidSessionStateValue())
-            {
-                Context.OnError(CurrentLocation, noValueError);
-            }
-
-            // Pull out the type name
-            var sessionStateValue = String.Concat(
-                Span.Symbols
-                    .Cast<CSharpSymbol>()
-                    .Select(sym => sym.Content)).Trim();
-
-            // Set up code generation
-            Span.CodeGenerator = createCodeGenerator(SyntaxConstants.CSharp.SessionStateKeyword, sessionStateValue);
-
-            // Output the span and finish the block
-            CompleteBlock();
-            Output(SpanKind.Code);
-        }
-
-        protected virtual bool ValidSessionStateValue()
-        {
-            return Optional(CSharpSymbolType.Identifier);
-        }
-
         [SuppressMessage("Microsoft.Maintainability", "CA1506:AvoidExcessiveClassCoupling", Justification = "Coupling will be reviewed at a later date")]
         [SuppressMessage("Microsoft.Globalization", "CA1308:NormalizeStringsToUppercase", Justification = "C# Keywords are always lower-case")]
         protected virtual void HelperDirective()

src/Microsoft.AspNet.Razor/Parser/CSharpCodeParser.cs

@@ -37,7 +37,6 @@ namespace Microsoft.AspNet.Razor.Parser
             "namespace",
             "class",
             "layout",
-            "sessionstate"
         };
 
         private Dictionary<string, Action> _directiveParsers = new Dictionary<string, Action>();

src/Microsoft.AspNet.Razor/Parser/ParserContext.cs

@@ -230,7 +230,7 @@ namespace Microsoft.AspNet.Razor.Parser
                                      // TagHelperDescriptors are not found by default. The RazorParser is responsible 
                                      // for identifying TagHelperDescriptors and rebuilding ParserResults.
                                      tagHelperDescriptors: Enumerable.Empty<TagHelperDescriptor>(),
-                                     parserErrors: _errorSink.Errors.ToList());
+                                     errorSink: _errorSink);
         }
 
         [Conditional("DEBUG")]

src/Microsoft.AspNet.Razor/Parser/RazorParser.cs

@@ -197,7 +197,7 @@ namespace Microsoft.AspNet.Razor.Parser
             }
 
             // Return the new result
-            return new ParserResults(syntaxTree, descriptors, errorSink.Errors.ToList());
+            return new ParserResults(syntaxTree, descriptors, errorSink);
         }
 
         /// <summary>

src/Microsoft.AspNet.Razor/Parser/SyntaxConstants.cs

@@ -28,7 +28,6 @@ namespace Microsoft.AspNet.Razor.Parser
             public static readonly string NamespaceKeyword = "namespace";
             public static readonly string ClassKeyword = "class";
             public static readonly string LayoutKeyword = "layout";
-            public static readonly string SessionStateKeyword = "sessionstate";
         }
     }
 }

src/Microsoft.AspNet.Razor/Parser/TagHelpers/TagHelperBlock.cs

@@ -6,6 +6,7 @@ using System.Collections.Generic;
 using System.Globalization;
 using System.Linq;
 using Microsoft.AspNet.Razor.Parser.SyntaxTree;
+using Microsoft.AspNet.Razor.TagHelpers;
 using Microsoft.AspNet.Razor.Text;
 using Microsoft.Internal.Web.Utils;
 
@@ -27,6 +28,7 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers
             : base(source.Type, source.Children, source.CodeGenerator)
         {
             TagName = source.TagName;
+            Descriptors = source.Descriptors;
             Attributes = new Dictionary<string, SyntaxTreeNode>(source.Attributes);
             _start = source.Start;
 
@@ -38,6 +40,11 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers
             }
         }
 
+        /// <summary>
+        /// <see cref="TagHelperDescriptor"/>s for the HTML element.
+        /// </summary>
+        public IEnumerable<TagHelperDescriptor> Descriptors { get; }
+
         /// <summary>
         /// The HTML attributes.
         /// </summary>

src/Microsoft.AspNet.Razor/Parser/TagHelpers/TagHelperBlockBuilder.cs

@@ -1,14 +1,11 @@
 // Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-using System;
 using System.Collections.Generic;
-using System.Linq;
 using Microsoft.AspNet.Razor.Generator;
 using Microsoft.AspNet.Razor.Parser.SyntaxTree;
 using Microsoft.AspNet.Razor.TagHelpers;
 using Microsoft.AspNet.Razor.Text;
-using Microsoft.AspNet.Razor.Tokenizer.Symbols;
 
 namespace Microsoft.AspNet.Razor.Parser.TagHelpers
 {
@@ -18,7 +15,7 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers
     public class TagHelperBlockBuilder : BlockBuilder
     {
         /// <summary>
-        /// Instantiates a new <see cref="TagHelperBlockBuilder"/> instance based on given the
+        /// Instantiates a new <see cref="TagHelperBlockBuilder"/> instance based on the given
         /// <paramref name="original"/>.
         /// </summary>
         /// <param name="original">The original <see cref="TagHelperBlock"/> to copy data from.</param>
@@ -26,6 +23,7 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers
             : base(original)
         {
             TagName = original.TagName;
+            Descriptors = original.Descriptors;
             Attributes = new Dictionary<string, SyntaxTreeNode>(original.Attributes);
         }
 
@@ -35,19 +33,21 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers
         /// and <see cref="BlockBuilder.Type"/> from the <paramref name="startTag"/>.
         /// </summary>
         /// <param name="tagName">An HTML tag name.</param>
+        /// <param name="start">Starting location of the <see cref="TagHelperBlock"/>.</param>
+        /// <param name="attributes">Attributes of the <see cref="TagHelperBlock"/>.</param>
         /// <param name="descriptors">The <see cref="TagHelperDescriptor"/>s associated with the current HTML
         /// tag.</param>
-        /// <param name="startTag">The <see cref="Block"/> that contains all information about the start
-        /// of the HTML element.</param>
-        public TagHelperBlockBuilder(string tagName, IEnumerable<TagHelperDescriptor> descriptors, Block startTag)
+        public TagHelperBlockBuilder(string tagName,
+                                     SourceLocation start,
+                                     IDictionary<string, SyntaxTreeNode> attributes,
+                                     IEnumerable<TagHelperDescriptor> descriptors)
         {
             TagName = tagName;
+            Start = start;
+            Descriptors = descriptors;
+            Type = BlockType.Tag;
             CodeGenerator = new TagHelperCodeGenerator(descriptors);
-            Type = startTag.Type;
-            Attributes = GetTagAttributes(startTag, descriptors);
-
-            // There will always be at least one child for the '<'.
-            Start = startTag.Children.First().Start;
+            Attributes = new Dictionary<string, SyntaxTreeNode>(attributes);
         }
 
         // Internal for testing
@@ -67,6 +67,11 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers
             }
         }
 
+        /// <summary>
+        /// <see cref="TagHelperDescriptor"/>s for the HTML element.
+        /// </summary>
+        public IEnumerable<TagHelperDescriptor> Descriptors { get; }
+
         /// <summary>
         /// The HTML attributes.
         /// </summary>
@@ -106,280 +111,5 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers
         /// The starting <see cref="SourceLocation"/> of the tag helper.
         /// </summary>
         public SourceLocation Start { get; private set; }
-
-        private static IDictionary<string, SyntaxTreeNode> GetTagAttributes(
-            Block tagBlock,
-            IEnumerable<TagHelperDescriptor> descriptors)
-        {
-            var attributes = new Dictionary<string, SyntaxTreeNode>(StringComparer.OrdinalIgnoreCase);
-
-            // Build a dictionary so we can easily lookup expected attribute value lookups
-            IReadOnlyDictionary<string, string> attributeValueTypes = 
-                descriptors.SelectMany(descriptor => descriptor.Attributes)
-                           .Distinct(TagHelperAttributeDescriptorComparer.Default)
-                           .ToDictionary(descriptor => descriptor.Name,
-                                       descriptor => descriptor.TypeName,
-                                       StringComparer.OrdinalIgnoreCase);
-
-            // We skip the first child "<tagname" and take everything up to the "ending" portion of the tag ">" or "/>".
-            // The -2 accounts for both the start and end tags.
-            var attributeChildren = tagBlock.Children.Skip(1).Take(tagBlock.Children.Count() - 2);
-
-            foreach (var child in attributeChildren)
-            {
-                KeyValuePair<string, SyntaxTreeNode> attribute;
-
-                if (child.IsBlock)
-                {
-                    attribute = ParseBlock((Block)child, attributeValueTypes);
-                }
-                else
-                {
-                    attribute = ParseSpan((Span)child, attributeValueTypes);
-                }
-
-                attributes.Add(attribute.Key, attribute.Value);
-            }
-
-            return attributes;
-        }
-
-        // This method handles cases when the attribute is a simple span attribute such as
-        // class="something moresomething".  This does not handle complex attributes such as
-        // class="@myclass". Therefore the span.Content is equivalent to the entire attribute.
-        private static KeyValuePair<string, SyntaxTreeNode> ParseSpan(
-            Span span,
-            IReadOnlyDictionary<string, string> attributeValueTypes)
-        {
-            var afterEquals = false;
-            var builder = new SpanBuilder
-            {
-                CodeGenerator = span.CodeGenerator,
-                EditHandler = span.EditHandler,
-                Kind = span.Kind
-            };
-            var htmlSymbols = span.Symbols.OfType<HtmlSymbol>().ToArray();
-            var symbolOffset = 1;
-            string name = null;
-
-            // Iterate down through the symbols to find the name and the start of the value.
-            // We subtract the symbolOffset so we don't accept an ending quote of a span.
-            for (var i = 0; i < htmlSymbols.Length - symbolOffset; i++)
-            {
-                var symbol = htmlSymbols[i];
-
-                if (name == null && symbol.Type == HtmlSymbolType.Text)
-                {
-                    name = symbol.Content;
-                }
-                else if (afterEquals)
-                {
-                    builder.Accept(symbol);
-                }
-                else if (symbol.Type == HtmlSymbolType.Equals)
-                {
-                    // We've found an '=' symbol, this means that the coming symbols will either be a quote
-                    // or value (in the case that the value is unquoted).
-                    // Spaces after/before the equal symbol are not yet supported:
-                    // https://github.com/aspnet/Razor/issues/123
-
-                    // TODO: Handle malformed tags, if there's an '=' then there MUST be a value.
-                    // https://github.com/aspnet/Razor/issues/104
-
-                    // Check for attribute start values, aka single or double quote
-                    if (IsQuote(htmlSymbols[i + 1]))
-                    {
-                        // Move past the attribute start so we can accept the true value.
-                        i++;
-                    }
-                    else
-                    {
-                        // Set the symbol offset to 0 so we don't attempt to skip an end quote that doesn't exist.
-                        symbolOffset = 0;
-                    }
-
-                    afterEquals = true;
-                }
-            }
-
-            return CreateMarkupAttribute(name, builder, attributeValueTypes);
-        }
-
-        private static KeyValuePair<string, SyntaxTreeNode> ParseBlock(
-            Block block,
-            IReadOnlyDictionary<string, string> attributeValueTypes)
-        {
-            // TODO: Accept more than just spans: https://github.com/aspnet/Razor/issues/96.
-            // The first child will only ever NOT be a Span if a user is doing something like:
-            // <input @checked />
-
-            var childSpan = block.Children.First() as Span;
-
-            if (childSpan == null)
-            {
-                throw new InvalidOperationException(RazorResources.TagHelpers_CannotHaveCSharpInTagDeclaration);
-            }
-
-            var builder = new BlockBuilder(block);
-
-            // If there's only 1 child it means that it's plain text inside of the attribute.
-            // i.e. <div class="plain text in attribute">
-            if (builder.Children.Count == 1)
-            {
-                return ParseSpan(childSpan, attributeValueTypes);
-            }
-
-            var textSymbol = childSpan.Symbols.FirstHtmlSymbolAs(HtmlSymbolType.Text);
-            var name = textSymbol != null ? textSymbol.Content : null;
-
-            if (name == null)
-            {
-                throw new InvalidOperationException(RazorResources.TagHelpers_AttributesMustHaveAName);
-            }
-
-            // Remove first child i.e. foo="
-            builder.Children.RemoveAt(0);
-
-            // Grabbing last child to check if the attribute value is quoted.
-            var endNode = block.Children.Last();
-            if (!endNode.IsBlock)
-            {
-                var endSpan = (Span)endNode;
-                var endSymbol = (HtmlSymbol)endSpan.Symbols.Last();
-
-                // Checking to see if it's a quoted attribute, if so we should remove end quote
-                if (IsQuote(endSymbol))
-                {
-                    builder.Children.RemoveAt(builder.Children.Count - 1);
-                }
-            }
-
-            // We need to rebuild the code generators of the builder and its children (this is needed to
-            // ensure we don't do special attribute code generation since this is a tag helper).
-            block = RebuildCodeGenerators(builder.Build());
-
-            // If there's only 1 child at this point its value could be a simple markup span (treated differently than
-            // block level elements for attributes).
-            if (block.Children.Count() == 1)
-            {
-                var child = block.Children.First() as Span;
-
-                if (child != null)
-                {
-                    // After pulling apart the block we just have a value span.
-
-                    var spanBuilder = new SpanBuilder(child);
-
-                    return CreateMarkupAttribute(name, spanBuilder, attributeValueTypes);
-                }
-            }
-
-            return new KeyValuePair<string, SyntaxTreeNode>(name, block);
-        }
-
-        private static Block RebuildCodeGenerators(Block block)
-        {
-            var builder = new BlockBuilder(block);
-
-            var isDynamic = builder.CodeGenerator is DynamicAttributeBlockCodeGenerator;
-
-            // We don't want any attribute specific logic here, null out the block code generator.
-            if (isDynamic || builder.CodeGenerator is AttributeBlockCodeGenerator)
-            {
-                builder.CodeGenerator = BlockCodeGenerator.Null;
-            }
-
-            for (var i = 0; i < builder.Children.Count; i++)
-            {
-                var child = builder.Children[i];
-
-                if (child.IsBlock)
-                {
-                    // The child is a block, recurse down into the block to rebuild its children
-                    builder.Children[i] = RebuildCodeGenerators((Block)child);
-                }
-                else
-                {
-                    var childSpan = (Span)child;
-                    ISpanCodeGenerator newCodeGenerator = null;
-                    var literalGenerator = childSpan.CodeGenerator as LiteralAttributeCodeGenerator;
-
-                    if (literalGenerator != null)
-                    {
-                        if (literalGenerator.ValueGenerator == null || literalGenerator.ValueGenerator.Value == null)
-                        {
-                            newCodeGenerator = new MarkupCodeGenerator();
-                        }
-                        else
-                        {
-                            newCodeGenerator = literalGenerator.ValueGenerator.Value;
-                        }
-                    }
-                    else if (isDynamic && childSpan.CodeGenerator == SpanCodeGenerator.Null)
-                    {
-                        // Usually the dynamic code generator handles rendering the null code generators underneath
-                        // it. This doesn't make sense in terms of tag helpers though, we need to change null code
-                        // generators to markup code generators.
-
-                        newCodeGenerator = new MarkupCodeGenerator();
-                    }
-
-                    // If we have a new code generator we'll need to re-build the child
-                    if (newCodeGenerator != null)
-                    {
-                        var childSpanBuilder = new SpanBuilder(childSpan)
-                        {
-                            CodeGenerator = newCodeGenerator
-                        };
-
-                        builder.Children[i] = childSpanBuilder.Build();
-                    }
-                }
-            }
-
-            return builder.Build();
-        }
-
-        private static KeyValuePair<string, SyntaxTreeNode> CreateMarkupAttribute(
-            string name, 
-            SpanBuilder builder,
-            IReadOnlyDictionary<string, string> attributeValueTypes)
-        {
-            string attributeTypeName;
-
-            // If the attribute was requested by the tag helper and doesn't happen to be a string then we need to treat
-            // its value as code. Any non-string value can be any C# value so we need to ensure the SyntaxTreeNode
-            // reflects that.
-            if (attributeValueTypes.TryGetValue(name, out attributeTypeName) &&
-                !string.Equals(attributeTypeName, typeof(string).FullName, StringComparison.OrdinalIgnoreCase))
-            {
-                builder.Kind = SpanKind.Code;
-            }
-
-            return new KeyValuePair<string, SyntaxTreeNode>(name, builder.Build());
-        }
-
-        private static bool IsQuote(HtmlSymbol htmlSymbol)
-        {
-            return htmlSymbol.Type == HtmlSymbolType.DoubleQuote ||
-                   htmlSymbol.Type == HtmlSymbolType.SingleQuote;
-        }
-
-        // This class is used to compare tag helper attributes by comparing only the HTML attribute name.
-        private class TagHelperAttributeDescriptorComparer : IEqualityComparer<TagHelperAttributeDescriptor>
-        {
-            public static readonly TagHelperAttributeDescriptorComparer Default =
-                new TagHelperAttributeDescriptorComparer();
-
-            public bool Equals(TagHelperAttributeDescriptor descriptorX, TagHelperAttributeDescriptor descriptorY)
-            {
-                return string.Equals(descriptorX.Name, descriptorY.Name, StringComparison.OrdinalIgnoreCase);
-            }
-
-            public int GetHashCode(TagHelperAttributeDescriptor descriptor)
-            {
-                return StringComparer.OrdinalIgnoreCase.GetHashCode(descriptor.Name);
-            }
-        }
     }
 }

src/Microsoft.AspNet.Razor/Parser/TagHelpers/TagHelperBlockRewriter.cs

@@ -0,0 +1,375 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.AspNet.Razor.Generator;
+using Microsoft.AspNet.Razor.Parser.SyntaxTree;
+using Microsoft.AspNet.Razor.TagHelpers;
+using Microsoft.AspNet.Razor.Text;
+using Microsoft.AspNet.Razor.Tokenizer.Symbols;
+
+namespace Microsoft.AspNet.Razor.Parser.TagHelpers.Internal
+{
+    public static class TagHelperBlockRewriter
+    {
+        public static TagHelperBlockBuilder Rewrite(string tagName,
+                                                    bool validStructure,
+                                                    Block tag,
+                                                    IEnumerable<TagHelperDescriptor> descriptors,
+                                                    ParserErrorSink errorSink)
+        {
+            // There will always be at least one child for the '<'.
+            var start = tag.Children.First().Start;
+            var attributes = GetTagAttributes(tagName, validStructure, tag, descriptors, errorSink);
+
+            return new TagHelperBlockBuilder(tagName, start, attributes, descriptors);
+        }
+
+        private static IDictionary<string, SyntaxTreeNode> GetTagAttributes(
+            string tagName,
+            bool validStructure,
+            Block tagBlock,
+            IEnumerable<TagHelperDescriptor> descriptors,
+            ParserErrorSink errorSink)
+        {
+            var attributes = new Dictionary<string, SyntaxTreeNode>(StringComparer.OrdinalIgnoreCase);
+
+            // Build a dictionary so we can easily lookup expected attribute value lookups
+            IReadOnlyDictionary<string, string> attributeValueTypes =
+                descriptors.SelectMany(descriptor => descriptor.Attributes)
+                           .Distinct(TagHelperAttributeDescriptorComparer.Default)
+                           .ToDictionary(descriptor => descriptor.Name,
+                                       descriptor => descriptor.TypeName,
+                                       StringComparer.OrdinalIgnoreCase);
+
+            // We skip the first child "<tagname" and take everything up to the ending portion of the tag ">" or "/>".
+            // The -2 accounts for both the start and end tags. If the tag does not have a valid structure then there's
+            // no end tag to ignore.
+            var symbolOffset = validStructure ? 2 : 1;
+            var attributeChildren = tagBlock.Children.Skip(1).Take(tagBlock.Children.Count() - symbolOffset);
+
+            foreach (var child in attributeChildren)
+            {
+                KeyValuePair<string, SyntaxTreeNode> attribute;
+                bool succeeded = true;
+
+                if (child.IsBlock)
+                {
+                    succeeded = TryParseBlock(tagName, (Block)child, attributeValueTypes, errorSink, out attribute);
+                }
+                else
+                {
+                    succeeded = TryParseSpan((Span)child, attributeValueTypes, errorSink, out attribute);
+                }
+
+                // Only want to track the attribute if we succeeded in parsing its corresponding Block/Span.
+                if (succeeded)
+                {
+                    attributes[attribute.Key] = attribute.Value;
+                }
+            }
+
+            return attributes;
+        }
+
+        // This method handles cases when the attribute is a simple span attribute such as
+        // class="something moresomething".  This does not handle complex attributes such as
+        // class="@myclass". Therefore the span.Content is equivalent to the entire attribute.
+        private static bool TryParseSpan(
+            Span span,
+            IReadOnlyDictionary<string, string> attributeValueTypes,
+            ParserErrorSink errorSink,
+            out KeyValuePair<string, SyntaxTreeNode> attribute)
+        {
+            var afterEquals = false;
+            var builder = new SpanBuilder
+            {
+                CodeGenerator = span.CodeGenerator,
+                EditHandler = span.EditHandler,
+                Kind = span.Kind
+            };
+            var htmlSymbols = span.Symbols.OfType<HtmlSymbol>().ToArray();
+            var capturedAttributeValueStart = false;
+            var attributeValueStartLocation = span.Start;
+            var symbolOffset = 1;
+            string name = null;
+
+            // Iterate down through the symbols to find the name and the start of the value.
+            // We subtract the symbolOffset so we don't accept an ending quote of a span.
+            for (var i = 0; i < htmlSymbols.Length - symbolOffset; i++)
+            {
+                var symbol = htmlSymbols[i];
+
+                if (afterEquals)
+                {
+                    // When symbols are accepted into SpanBuilders, their locations get altered to be offset by the 
+                    // parent which is why we need to mark our start location prior to adding the symbol. 
+                    // This is needed to know the location of the attribute value start within the document.
+                    if (!capturedAttributeValueStart)
+                    {
+                        capturedAttributeValueStart = true;
+
+                        attributeValueStartLocation = span.Start + symbol.Start;
+                    }
+
+                    builder.Accept(symbol);
+                }
+                else if (name == null && symbol.Type == HtmlSymbolType.Text)
+                {
+                    name = symbol.Content;
+                    attributeValueStartLocation = SourceLocation.Advance(span.Start, name);
+                }
+                else if (symbol.Type == HtmlSymbolType.Equals)
+                {
+                    // We've found an '=' symbol, this means that the coming symbols will either be a quote
+                    // or value (in the case that the value is unquoted).
+                    // Spaces after/before the equal symbol are not yet supported:
+                    // https://github.com/aspnet/Razor/issues/123
+
+                    // TODO: Handle malformed tags, if there's an '=' then there MUST be a value.
+                    // https://github.com/aspnet/Razor/issues/104
+
+                    SourceLocation symbolStartLocation;
+
+                    // Check for attribute start values, aka single or double quote
+                    if (IsQuote(htmlSymbols[i + 1]))
+                    {
+                        // Move past the attribute start so we can accept the true value.
+                        i++;
+                        symbolStartLocation = htmlSymbols[i + 1].Start;
+                    }
+                    else
+                    {
+                        symbolStartLocation = symbol.Start;
+
+                        // Set the symbol offset to 0 so we don't attempt to skip an end quote that doesn't exist.
+                        symbolOffset = 0;
+                    }
+
+                    attributeValueStartLocation = symbolStartLocation +
+                                                  span.Start +
+                                                  new SourceLocation(absoluteIndex: 1,
+                                                                     lineIndex: 0,
+                                                                     characterIndex: 1);
+                    afterEquals = true;
+                }
+            }
+
+            // After all symbols have been added we need to set the builders start position so we do not indirectly
+            // modify each symbol's Start location.
+            builder.Start = attributeValueStartLocation;
+
+            if (name == null)
+            {
+                errorSink.OnError(span.Start,
+                                  RazorResources.TagHelperBlockRewriter_TagHelperAttributesMustBeWelformed,
+                                  span.Content.Length);
+
+                attribute = default(KeyValuePair<string, SyntaxTreeNode>);
+
+                return false;
+            }
+
+            attribute = CreateMarkupAttribute(name, builder, attributeValueTypes);
+
+            return true;
+        }
+
+        private static bool TryParseBlock(
+            string tagName,
+            Block block,
+            IReadOnlyDictionary<string, string> attributeValueTypes,
+            ParserErrorSink errorSink,
+            out KeyValuePair<string, SyntaxTreeNode> attribute)
+        {
+            // TODO: Accept more than just spans: https://github.com/aspnet/Razor/issues/96.
+            // The first child will only ever NOT be a Span if a user is doing something like:
+            // <input @checked />
+
+            var childSpan = block.Children.First() as Span;
+
+            if (childSpan == null || childSpan.Kind != SpanKind.Markup)
+            {
+                errorSink.OnError(block.Children.First().Start,
+                                  RazorResources.FormatTagHelpers_CannotHaveCSharpInTagDeclaration(tagName));
+
+                attribute = default(KeyValuePair<string, SyntaxTreeNode>);
+
+                return false;
+            }
+
+            var builder = new BlockBuilder(block);
+
+            // If there's only 1 child it means that it's plain text inside of the attribute.
+            // i.e. <div class="plain text in attribute">
+            if (builder.Children.Count == 1)
+            {
+                return TryParseSpan(childSpan, attributeValueTypes, errorSink, out attribute);
+            }
+
+            var textSymbol = childSpan.Symbols.FirstHtmlSymbolAs(HtmlSymbolType.Text);
+            var name = textSymbol != null ? textSymbol.Content : null;
+
+            if (name == null)
+            {
+                errorSink.OnError(childSpan.Start, RazorResources.FormatTagHelpers_AttributesMustHaveAName(tagName));
+
+                attribute = default(KeyValuePair<string, SyntaxTreeNode>);
+
+                return false;
+            }
+
+            // TODO: Support no attribute values: https://github.com/aspnet/Razor/issues/220
+
+            // Remove first child i.e. foo="
+            builder.Children.RemoveAt(0);
+
+            // Grabbing last child to check if the attribute value is quoted.
+            var endNode = block.Children.Last();
+            if (!endNode.IsBlock)
+            {
+                var endSpan = (Span)endNode;
+                var endSymbol = (HtmlSymbol)endSpan.Symbols.Last();
+
+                // Checking to see if it's a quoted attribute, if so we should remove end quote
+                if (IsQuote(endSymbol))
+                {
+                    builder.Children.RemoveAt(builder.Children.Count - 1);
+                }
+            }
+
+            // We need to rebuild the code generators of the builder and its children (this is needed to
+            // ensure we don't do special attribute code generation since this is a tag helper).
+            block = RebuildCodeGenerators(builder.Build());
+
+            // If there's only 1 child at this point its value could be a simple markup span (treated differently than
+            // block level elements for attributes).
+            if (block.Children.Count() == 1)
+            {
+                var child = block.Children.First() as Span;
+
+                if (child != null)
+                {
+                    // After pulling apart the block we just have a value span.
+
+                    var spanBuilder = new SpanBuilder(child);
+
+                    attribute = CreateMarkupAttribute(name, spanBuilder, attributeValueTypes);
+
+                    return true;
+                }
+            }
+
+            attribute = new KeyValuePair<string, SyntaxTreeNode>(name, block);
+
+            return true;
+        }
+
+        private static Block RebuildCodeGenerators(Block block)
+        {
+            var builder = new BlockBuilder(block);
+
+            var isDynamic = builder.CodeGenerator is DynamicAttributeBlockCodeGenerator;
+
+            // We don't want any attribute specific logic here, null out the block code generator.
+            if (isDynamic || builder.CodeGenerator is AttributeBlockCodeGenerator)
+            {
+                builder.CodeGenerator = BlockCodeGenerator.Null;
+            }
+
+            for (var i = 0; i < builder.Children.Count; i++)
+            {
+                var child = builder.Children[i];
+
+                if (child.IsBlock)
+                {
+                    // The child is a block, recurse down into the block to rebuild its children
+                    builder.Children[i] = RebuildCodeGenerators((Block)child);
+                }
+                else
+                {
+                    var childSpan = (Span)child;
+                    ISpanCodeGenerator newCodeGenerator = null;
+                    var literalGenerator = childSpan.CodeGenerator as LiteralAttributeCodeGenerator;
+
+                    if (literalGenerator != null)
+                    {
+                        if (literalGenerator.ValueGenerator == null || literalGenerator.ValueGenerator.Value == null)
+                        {
+                            newCodeGenerator = new MarkupCodeGenerator();
+                        }
+                        else
+                        {
+                            newCodeGenerator = literalGenerator.ValueGenerator.Value;
+                        }
+                    }
+                    else if (isDynamic && childSpan.CodeGenerator == SpanCodeGenerator.Null)
+                    {
+                        // Usually the dynamic code generator handles rendering the null code generators underneath
+                        // it. This doesn't make sense in terms of tag helpers though, we need to change null code 
+                        // generators to markup code generators.
+
+                        newCodeGenerator = new MarkupCodeGenerator();
+                    }
+
+                    // If we have a new code generator we'll need to re-build the child
+                    if (newCodeGenerator != null)
+                    {
+                        var childSpanBuilder = new SpanBuilder(childSpan)
+                        {
+                            CodeGenerator = newCodeGenerator
+                        };
+
+                        builder.Children[i] = childSpanBuilder.Build();
+                    }
+                }
+            }
+
+            return builder.Build();
+        }
+
+        private static KeyValuePair<string, SyntaxTreeNode> CreateMarkupAttribute(
+            string name,
+            SpanBuilder builder,
+            IReadOnlyDictionary<string, string> attributeValueTypes)
+        {
+            string attributeTypeName;
+
+            // If the attribute was requested by the tag helper and doesn't happen to be a string then we need to treat
+            // its value as code. Any non-string value can be any C# value so we need to ensure the SyntaxTreeNode
+            // reflects that.
+            if (attributeValueTypes.TryGetValue(name, out attributeTypeName) &&
+                !string.Equals(attributeTypeName, typeof(string).FullName, StringComparison.OrdinalIgnoreCase))
+            {
+                builder.Kind = SpanKind.Code;
+            }
+
+            return new KeyValuePair<string, SyntaxTreeNode>(name, builder.Build());
+        }
+
+        private static bool IsQuote(HtmlSymbol htmlSymbol)
+        {
+            return htmlSymbol.Type == HtmlSymbolType.DoubleQuote ||
+                   htmlSymbol.Type == HtmlSymbolType.SingleQuote;
+        }
+
+        // This class is used to compare tag helper attributes by comparing only the HTML attribute name.
+        private class TagHelperAttributeDescriptorComparer : IEqualityComparer<TagHelperAttributeDescriptor>
+        {
+            public static readonly TagHelperAttributeDescriptorComparer Default =
+                new TagHelperAttributeDescriptorComparer();
+
+            public bool Equals(TagHelperAttributeDescriptor descriptorX, TagHelperAttributeDescriptor descriptorY)
+            {
+                return string.Equals(descriptorX.Name, descriptorY.Name, StringComparison.OrdinalIgnoreCase);
+            }
+
+            public int GetHashCode(TagHelperAttributeDescriptor descriptor)
+            {
+                return StringComparer.OrdinalIgnoreCase.GetHashCode(descriptor.Name);
+            }
+        }
+    }
+}

src/Microsoft.AspNet.Razor/Parser/TagHelpers/TagHelperParseTreeRewriter.cs

@@ -27,14 +27,12 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers.Internal
 
         public void Rewrite(RewritingContext context)
         {
-            RewriteTags(context.SyntaxTree);
-
-            ValidateRewrittenSyntaxTree(context);
+            RewriteTags(context.SyntaxTree, context);
 
             context.SyntaxTree = _currentBlock.Build();
         }
 
-        private void RewriteTags(Block input)
+        private void RewriteTags(Block input, RewritingContext context)
         {
             // We want to start a new block without the children from existing (we rebuild them).
             TrackBlock(new BlockBuilder
@@ -43,6 +41,8 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers.Internal
                 CodeGenerator = input.CodeGenerator
             });
 
+            var activeTagHelpers = _tagStack.Count;
+
             foreach (var child in input.Children)
             {
                 if (child.IsBlock)
@@ -51,65 +51,18 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers.Internal
 
                     if (childBlock.Type == BlockType.Tag)
                     {
-                        // TODO: Fully handle malformed tags: https://github.com/aspnet/Razor/issues/104
-
-                        // Get tag name of the current block (doesn't matter if it's an end or start tag)
-                        var tagName = GetTagName(childBlock);
-
-                        // Could not determine tag name, it can't be a TagHelper, continue on and track the element.
-                        if (tagName == null)
+                        if (TryRewriteTagHelper(childBlock, context))
                         {
-                            _currentBlock.Children.Add(child);
                             continue;
                         }
 
-                        if (!IsEndTag(childBlock))
-                        {
-                            // We're in a begin tag block
-
-                            if (IsPotentialTagHelper(tagName, childBlock))
-                            {
-                                var descriptors = _provider.GetTagHelpers(tagName);
-
-                                // We could be a tag helper, but only if we have descriptors registered
-                                if (descriptors.Any())
-                                {
-                                    // Found a new tag helper block
-                                    TrackTagHelperBlock(new TagHelperBlockBuilder(tagName, descriptors, childBlock));
-
-                                    // If it's a self closing block then we don't have to worry about nested children
-                                    // within the tag... complete it.
-                                    if (IsSelfClosing(childBlock))
-                                    {
-                                        BuildCurrentlyTrackedTagHelperBlock();
-                                    }
-
-                                    continue;
-                                }
-                            }
-                        }
-                        else
-                        {
-                            var currentTagHelper = _tagStack.Count > 0 ? _tagStack.Peek() : null;
-
-                            // Check if it's an "end" tag helper that matches our current tag helper
-                            if (currentTagHelper != null &&
-                                string.Equals(currentTagHelper.TagName, tagName, StringComparison.OrdinalIgnoreCase))
-                            {
-                                BuildCurrentlyTrackedTagHelperBlock();
-                                continue;
-                            }
-
-                            // We're in an end tag, there won't be anymore tag helpers nested.
-                        }
-
-                        // If we get to here it means that we're a normal html tag.  No need to iterate
-                        // any deeper into the children of it because they wont be tag helpers.
+                        // If we get to here it means that we're a normal html tag.  No need to iterate any deeper into
+                        // the children of it because they wont be tag helpers.
                     }
                     else
                     {
                         // We're not an Html tag so iterate through children recursively.
-                        RewriteTags(childBlock);
+                        RewriteTags(childBlock, context);
                         continue;
                     }
                 }
@@ -117,42 +70,141 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers.Internal
                 // At this point the child is a Span or Block with Type BlockType.Tag that doesn't happen to be a
                 // tag helper.
 
-                // Add the child to current block.
+                // Add the child to current block. 
                 _currentBlock.Children.Add(child);
             }
 
+            // We captured the number of active tag helpers at the start of our logic, it should be the same. If not
+            // it means that there are malformed tag helpers at the top of our stack.
+            if (activeTagHelpers != _tagStack.Count)
+            {
+                // Malformed tag helpers built here will be tag helpers that do not have end tags in the current block 
+                // scope. Block scopes are special cases in Razor such as @<p> would cause an error because there's no
+                // matching end </p> tag in the template block scope and therefore doesn't make sense as a tag helper.
+                BuildMalformedTagHelpers(_tagStack.Count - activeTagHelpers, context);
+
+                Debug.Assert(activeTagHelpers == _tagStack.Count);
+            }
+
             BuildCurrentlyTrackedBlock();
         }
 
-        private void ValidateRewrittenSyntaxTree(RewritingContext context)
+        private bool TryRewriteTagHelper(Block tagBlock, RewritingContext context)
         {
-            // If the blockStack still has elements in it that means there's at least one malformed TagHelper block in
-            // the document, that's the only way we can have a non-zero _blockStack.Count.
-            if (_blockStack.Count != 0)
+            // TODO: Fully handle malformed tags: https://github.com/aspnet/Razor/issues/104
+
+            // Get tag name of the current block (doesn't matter if it's an end or start tag)
+            var tagName = GetTagName(tagBlock);
+
+            // Could not determine tag name, it can't be a TagHelper, continue on and track the element.
+            if (tagName == null)
             {
-                // We reverse the children so we can search from the back to the front for the TagHelper that is
-                // malformed.
-                var candidateChildren = _currentBlock.Children.Reverse();
-                var malformedTagHelper = candidateChildren.OfType<TagHelperBlock>().FirstOrDefault();
+                return false;
+            }
 
-                // If the malformed tag helper is null that means something other than a TagHelper caused the
-                // unbalancing of the syntax tree (should never happen).
-                Debug.Assert(malformedTagHelper != null);
+            var descriptors = Enumerable.Empty<TagHelperDescriptor>();
 
-                // We only create a single error because we can't reasonably determine other invalid tag helpers in the
-                // document; having one malformed tag helper puts the document into an invalid state.
-                context.ErrorSink.OnError(
-                    malformedTagHelper.Start,
-                    RazorResources.FormatTagHelpersParseTreeRewriter_FoundMalformedTagHelper(
-                        malformedTagHelper.TagName));
+            if (IsPotentialTagHelper(tagName, tagBlock))
+            {
+                descriptors = _provider.GetTagHelpers(tagName);
+            }
 
-                // We need to build the remaining blocks in the stack to ensure we don't return an invalid syntax tree.
-                do
+            // If there aren't any TagHelperDescriptors registered then we aren't a TagHelper
+            if (!descriptors.Any())
+            {
+                return false;
+            }
+
+            if (!IsEndTag(tagBlock))
+            {
+                // We're in a begin tag helper block
+
+                var validTagStructure = ValidTagStructure(tagName, tagBlock, context);
+
+                var builder = TagHelperBlockRewriter.Rewrite(tagName,
+                                                             validTagStructure,
+                                                             tagBlock,
+                                                             descriptors,
+                                                             context.ErrorSink);
+
+                // Found a new tag helper block
+                TrackTagHelperBlock(builder);
+
+                // If it's a self closing block then we don't have to worry about nested children 
+                // within the tag... complete it.
+                if (IsSelfClosing(tagBlock))
                 {
                     BuildCurrentlyTrackedTagHelperBlock();
                 }
-                while (_blockStack.Count != 0);
             }
+            else
+            {
+                // We're in an end tag helper block.
+
+                var tagNameScope = _tagStack.Count > 0 ? _tagStack.Peek().TagName : string.Empty;
+
+                // Validate that our end tag helper matches the currently scoped tag helper, if not we
+                // need to error.
+                if (tagNameScope.Equals(tagName, StringComparison.OrdinalIgnoreCase))
+                {
+                    ValidTagStructure(tagName, tagBlock, context);
+
+                    BuildCurrentlyTrackedTagHelperBlock();
+                }
+                else
+                {
+                    // Current tag helper scope does not match the end tag. Attempt to recover the tag 
+                    // helper by looking up the previous tag helper scopes for a matching tag. If we 
+                    // can't recover it means there was no corresponding tag helper begin tag.
+                    if (TryRecoverTagHelper(tagName, context))
+                    {
+                        ValidTagStructure(tagName, tagBlock, context);
+
+                        // Successfully recovered, move onto the next element.
+                    }
+                    else
+                    {
+                        // Could not recover, the end tag helper has no corresponding begin tag, create
+                        // an error based on the current childBlock.
+                        context.ErrorSink.OnError(
+                            tagBlock.Start,
+                            RazorResources.FormatTagHelpersParseTreeRewriter_FoundMalformedTagHelper(tagName));
+
+                        return false;
+                    }
+                }
+            }
+
+            return true;
+        }
+
+        private static bool ValidTagStructure(string tagName, Block tag, RewritingContext context)
+        {
+            // We assume an invalid structure until we verify that the tag meets all of our "valid structure" criteria.
+            var invalidStructure = true;
+
+            // No need to validate the tag end because in order to be a tag block it must start with '<'.
+            var tagEnd = tag.Children.Last() as Span;
+
+            // If our tag end is not a markup span it means it's some sort of code SyntaxTreeNode (not a valid format)
+            if (tagEnd != null && tagEnd.Kind == SpanKind.Markup)
+            {
+                var endSymbol = tagEnd.Symbols.LastOrDefault() as HtmlSymbol;
+
+                if (endSymbol != null && endSymbol.Type == HtmlSymbolType.CloseAngle)
+                {
+                    invalidStructure = false;
+                }
+            }
+
+            if (invalidStructure)
+            {
+                context.ErrorSink.OnError(
+                    tag.Start,
+                    RazorResources.FormatTagHelpersParseTreeRewriter_MissingCloseAngle(tagName));
+            }
+
+            return !invalidStructure;
         }
 
         private void BuildCurrentlyTrackedBlock()
@@ -216,6 +268,52 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers.Internal
             TrackBlock(builder);
         }
 
+        private bool TryRecoverTagHelper(string tagName, RewritingContext context)
+        {
+            var malformedTagHelperCount = 0;
+
+            foreach (var tag in _tagStack)
+            {
+                if (tag.TagName.Equals(tagName, StringComparison.OrdinalIgnoreCase))
+                {
+                    break;
+                }
+
+                malformedTagHelperCount++;
+            }
+
+            // If the malformedTagHelperCount == _tagStack.Count it means we couldn't find a begin tag for the tag 
+            // helper, can't recover.
+            if (malformedTagHelperCount != _tagStack.Count)
+            {
+                BuildMalformedTagHelpers(malformedTagHelperCount, context);
+
+                // One final build, this is the build that completes our target tag helper block which is not malformed.
+                BuildCurrentlyTrackedTagHelperBlock();
+
+                // We were able to recover
+                return true;
+            }
+
+            // Could not recover tag helper. Aka we found a tag helper end tag without a corresponding begin tag.
+            return false;
+        }
+
+        private void BuildMalformedTagHelpers(int count, RewritingContext context)
+        {
+            for (var i = 0; i < count; i++)
+            {
+                var malformedTagHelper = _tagStack.Peek();
+
+                context.ErrorSink.OnError(
+                    malformedTagHelper.Start,
+                    RazorResources.FormatTagHelpersParseTreeRewriter_FoundMalformedTagHelper(
+                        malformedTagHelper.TagName));
+
+                BuildCurrentlyTrackedTagHelperBlock();
+            }
+        }
+
         private static string GetTagName(Block tagBlock)
         {
             var child = tagBlock.Children.First();
@@ -240,9 +338,9 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers.Internal
         {
             EnsureTagBlock(beginTagBlock);
 
-            var childSpan = (Span)beginTagBlock.Children.Last();
+            var childSpan = beginTagBlock.Children.Last() as Span;
 
-            return childSpan.Content.EndsWith("/>");
+            return childSpan?.Content.EndsWith("/>") ?? false;
         }
 
         private static bool IsEndTag(Block tagBlock)

src/Microsoft.AspNet.Razor/ParserResults.cs

@@ -2,6 +2,8 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System.Collections.Generic;
+using System.Linq;
+using Microsoft.AspNet.Razor.Parser;
 using Microsoft.AspNet.Razor.Parser.SyntaxTree;
 using Microsoft.AspNet.Razor.TagHelpers;
 
@@ -15,15 +17,18 @@ namespace Microsoft.AspNet.Razor
         /// <summary>
         /// Instantiates a new <see cref="ParserResults"/> instance.
         /// </summary>
-        /// <param name="document">The Razor syntax tree.</param>
-        /// <param name="tagHelperDescriptors"><see cref="TagHelperDescriptor"/>s that apply to the current Razor 
-        /// document.</param>
-        /// <param name="parserErrors"><see cref="RazorError"/>s encountered when parsing the current Razor
-        /// document.</param>
+        /// <param name="document">The <see cref="Block"/> for the syntax tree.</param>
+        /// <param name="tagHelperDescriptors">
+        /// The <see cref="TagHelperDescriptor"/>s that apply to the current Razor document.
+        /// </param>
+        /// <param name="errorSink">
+        /// The <see cref="ParserErrorSink"/> used to collect <see cref="RazorError"/>s encountered when parsing the
+        /// current Razor document.
+        /// </param>
         public ParserResults([NotNull] Block document,
                              [NotNull] IEnumerable<TagHelperDescriptor> tagHelperDescriptors,
-                             [NotNull] IList<RazorError> parserErrors)
-            : this(parserErrors == null || parserErrors.Count == 0, document, tagHelperDescriptors, parserErrors)
+                             [NotNull] ParserErrorSink errorSink)
+            : this(!errorSink.Errors.Any(), document, tagHelperDescriptors, errorSink)
         {
         }
 
@@ -31,40 +36,50 @@ namespace Microsoft.AspNet.Razor
         /// Instantiates a new <see cref="ParserResults"/> instance.
         /// </summary>
         /// <param name="success"><c>true</c> if parsing was successful, <c>false</c> otherwise.</param>
-        /// <param name="document">The Razor syntax tree.</param>
-        /// <param name="tagHelperDescriptors"><see cref="TagHelperDescriptor"/>s that apply to the current Razor 
-        /// document.</param>
-        /// <param name="errors"><see cref="RazorError"/>s encountered when parsing the current Razor
-        /// document.</param>
+        /// <param name="document">The <see cref="Block"/> for the syntax tree.</param>
+        /// <param name="tagHelperDescriptors">
+        /// The <see cref="TagHelperDescriptor"/>s that apply to the current Razor document.
+        /// </param>
+        /// <param name="errorSink">
+        /// The <see cref="ParserErrorSink"/> used to collect <see cref="RazorError"/>s encountered when parsing the
+        /// current Razor document.
+        /// </param>
         protected ParserResults(bool success,
                                 [NotNull] Block document,
                                 [NotNull] IEnumerable<TagHelperDescriptor> tagHelperDescriptors,
-                                [NotNull] IList<RazorError> errors)
+                                [NotNull] ParserErrorSink errorSink)
         {
             Success = success;
             Document = document;
             TagHelperDescriptors = tagHelperDescriptors;
-            ParserErrors = errors ?? new List<RazorError>();
+            ErrorSink = errorSink;
+            ParserErrors = errorSink.Errors;
         }
 
         /// <summary>
-        /// Indicates if parsing was successful (no errors)
+        /// Indicates if parsing was successful (no errors).
         /// </summary>
-        public bool Success { get; private set; }
+        /// <value><c>true</c> if parsing was successful, <c>false</c> otherwise.</value>
+        public bool Success { get; }
 
         /// <summary>
-        /// The root node in the document's syntax tree
+        /// The root node in the document's syntax tree.
         /// </summary>
-        public Block Document { get; private set; }
+        public Block Document { get; }
+
+        /// <summary>
+        /// Used to aggregate <see cref="RazorError"/>s.
+        /// </summary>
+        public ParserErrorSink ErrorSink { get; }
 
         /// <summary>
         /// The list of errors which occurred during parsing.
         /// </summary>
-        public IList<RazorError> ParserErrors { get; private set; }
+        public IEnumerable<RazorError> ParserErrors { get; }
 
         /// <summary>
         /// The <see cref="TagHelperDescriptor"/>s found for the current Razor document.
         /// </summary>
-        public IEnumerable<TagHelperDescriptor> TagHelperDescriptors { get; private set; }
+        public IEnumerable<TagHelperDescriptor> TagHelperDescriptors { get; }
     }
 }

src/Microsoft.AspNet.Razor/Properties/RazorResources.Designer.cs

@@ -92,7 +92,7 @@ namespace Microsoft.AspNet.Razor
 
         /// <summary>
         /// The "@" character must be followed by a ":", "(", or a C# identifier.  If you intended to switch to markup, use an HTML start tag, for example:
-        ///
+        /// 
         /// @if(isLoggedIn) {
         ///     &lt;p&gt;Hello, @user!&lt;/p&gt;
         /// }
@@ -104,7 +104,7 @@ namespace Microsoft.AspNet.Razor
 
         /// <summary>
         /// The "@" character must be followed by a ":", "(", or a C# identifier.  If you intended to switch to markup, use an HTML start tag, for example:
-        ///
+        /// 
         /// @if(isLoggedIn) {
         ///     &lt;p&gt;Hello, @user!&lt;/p&gt;
         /// }
@@ -228,7 +228,7 @@ namespace Microsoft.AspNet.Razor
 
         /// <summary>
         /// Sections cannot be empty.  The "@section" keyword must be followed by a block of markup surrounded by "{}".  For example:
-        ///
+        /// 
         /// @section Sidebar {
         ///    &lt;!-- Markup and text goes here --&gt;
         /// }
@@ -240,7 +240,7 @@ namespace Microsoft.AspNet.Razor
 
         /// <summary>
         /// Sections cannot be empty.  The "@section" keyword must be followed by a block of markup surrounded by "{}".  For example:
-        ///
+        /// 
         /// @section Sidebar {
         ///    &lt;!-- Markup and text goes here --&gt;
         /// }
@@ -252,7 +252,7 @@ namespace Microsoft.AspNet.Razor
 
         /// <summary>
         /// Namespace imports and type aliases cannot be placed within code blocks.  They must immediately follow an "@" character in markup.  It is recommended that you put them at the top of the page, as in the following example:
-        ///
+        /// 
         /// @using System.Drawing;
         /// @{
         ///     // OK here to use types from System.Drawing in the page.
@@ -265,7 +265,7 @@ namespace Microsoft.AspNet.Razor
 
         /// <summary>
         /// Namespace imports and type aliases cannot be placed within code blocks.  They must immediately follow an "@" character in markup.  It is recommended that you put them at the top of the page, as in the following example:
-        ///
+        /// 
         /// @using System.Drawing;
         /// @{
         ///     // OK here to use types from System.Drawing in the page.
@@ -278,12 +278,12 @@ namespace Microsoft.AspNet.Razor
 
         /// <summary>
         /// Expected a "{0}" but found a "{1}".  Block statements must be enclosed in "{{" and "}}".  You cannot use single-statement control-flow statements in CSHTML pages. For example, the following is not allowed:
-        ///
+        /// 
         /// @if(isLoggedIn)
         ///     &lt;p&gt;Hello, @user&lt;/p&gt;
-        ///
+        /// 
         /// Instead, wrap the contents of the block in "{{}}":
-        ///
+        /// 
         /// @if(isLoggedIn) {{
         ///     &lt;p&gt;Hello, @user&lt;/p&gt;
         /// }}
@@ -295,12 +295,12 @@ namespace Microsoft.AspNet.Razor
 
         /// <summary>
         /// Expected a "{0}" but found a "{1}".  Block statements must be enclosed in "{{" and "}}".  You cannot use single-statement control-flow statements in CSHTML pages. For example, the following is not allowed:
-        ///
+        /// 
         /// @if(isLoggedIn)
         ///     &lt;p&gt;Hello, @user&lt;/p&gt;
-        ///
+        /// 
         /// Instead, wrap the contents of the block in "{{}}":
-        ///
+        /// 
         /// @if(isLoggedIn) {{
         ///     &lt;p&gt;Hello, @user&lt;/p&gt;
         /// }}
@@ -390,38 +390,6 @@ namespace Microsoft.AspNet.Razor
             return GetString("ParseError_Unterminated_String_Literal");
         }
 
-        /// <summary>
-        /// Unknown option: "{0}".
-        /// </summary>
-        internal static string ParseError_UnknownOption
-        {
-            get { return GetString("ParseError_UnknownOption"); }
-        }
-
-        /// <summary>
-        /// Unknown option: "{0}".
-        /// </summary>
-        internal static string FormatParseError_UnknownOption(object p0)
-        {
-            return string.Format(CultureInfo.CurrentCulture, GetString("ParseError_UnknownOption"), p0);
-        }
-
-        /// <summary>
-        /// The "{0}" block was not terminated.  All "{0}" statements must be terminated with a matching "{1}".
-        /// </summary>
-        internal static string ParseError_BlockNotTerminated
-        {
-            get { return GetString("ParseError_BlockNotTerminated"); }
-        }
-
-        /// <summary>
-        /// The "{0}" block was not terminated.  All "{0}" statements must be terminated with a matching "{1}".
-        /// </summary>
-        internal static string FormatParseError_BlockNotTerminated(object p0, object p1)
-        {
-            return string.Format(CultureInfo.CurrentCulture, GetString("ParseError_BlockNotTerminated"), p0, p1);
-        }
-
         /// <summary>
         /// @section Header { ... }
         /// </summary>
@@ -454,22 +422,6 @@ namespace Microsoft.AspNet.Razor
             return GetString("ParseError_TextTagCannotContainAttributes");
         }
 
-        /// <summary>
-        /// The "Imports" keyword must be followed by a namespace or a type alias on the same line.
-        /// </summary>
-        internal static string ParseError_NamespaceOrTypeAliasExpected
-        {
-            get { return GetString("ParseError_NamespaceOrTypeAliasExpected"); }
-        }
-
-        /// <summary>
-        /// The "Imports" keyword must be followed by a namespace or a type alias on the same line.
-        /// </summary>
-        internal static string FormatParseError_NamespaceOrTypeAliasExpected()
-        {
-            return GetString("ParseError_NamespaceOrTypeAliasExpected");
-        }
-
         /// <summary>
         /// A space or line break was encountered after the "@" character.  Only valid identifiers, keywords, comments, "(" and "{" are valid at the start of a code block and they must occur immediately following "@" with no space in between.
         /// </summary>
@@ -998,22 +950,6 @@ namespace Microsoft.AspNet.Razor
             return string.Format(CultureInfo.CurrentCulture, GetString("TokenizerView_CannotPutBack"), p0, p1);
         }
 
-        /// <summary>
-        /// Unexpected "{0}"
-        /// </summary>
-        internal static string ParseError_Unexpected
-        {
-            get { return GetString("ParseError_Unexpected"); }
-        }
-
-        /// <summary>
-        /// Unexpected "{0}"
-        /// </summary>
-        internal static string FormatParseError_Unexpected(object p0)
-        {
-            return string.Format(CultureInfo.CurrentCulture, GetString("ParseError_Unexpected"), p0);
-        }
-
         /// <summary>
         /// Unexpected "{" after "@" character. Once inside the body of a code block (@if {}, @{}, etc.) you do not need to use "@{" to switch to code.
         /// </summary>
@@ -1142,38 +1078,6 @@ namespace Microsoft.AspNet.Razor
             return GetString("Language_Does_Not_Support_RazorComment");
         }
 
-        /// <summary>
-        /// Missing value for session state directive.
-        /// </summary>
-        internal static string ParserEror_SessionDirectiveMissingValue
-        {
-            get { return GetString("ParserEror_SessionDirectiveMissingValue"); }
-        }
-
-        /// <summary>
-        /// Missing value for session state directive.
-        /// </summary>
-        internal static string FormatParserEror_SessionDirectiveMissingValue()
-        {
-            return GetString("ParserEror_SessionDirectiveMissingValue");
-        }
-
-        /// <summary>
-        /// Cannot call CreateCodeWriter, a CodeWriter was not provided to the Create method
-        /// </summary>
-        internal static string CreateCodeWriter_NoCodeWriter
-        {
-            get { return GetString("CreateCodeWriter_NoCodeWriter"); }
-        }
-
-        /// <summary>
-        /// Cannot call CreateCodeWriter, a CodeWriter was not provided to the Create method
-        /// </summary>
-        internal static string FormatCreateCodeWriter_NoCodeWriter()
-        {
-            return GetString("CreateCodeWriter_NoCodeWriter");
-        }
-
         /// <summary>
         /// [BG][{0}] Shutdown
         /// </summary>
@@ -1431,7 +1335,7 @@ namespace Microsoft.AspNet.Razor
         }
 
         /// <summary>
-        /// Tag Helper attributes must have a name.
+        /// Tag Helper '{0}'s attributes must have names.
         /// </summary>
         internal static string TagHelpers_AttributesMustHaveAName
         {
@@ -1439,15 +1343,15 @@ namespace Microsoft.AspNet.Razor
         }
 
         /// <summary>
-        /// Tag Helper attributes must have a name.
+        /// Tag Helper '{0}'s attributes must have names.
         /// </summary>
-        internal static string FormatTagHelpers_AttributesMustHaveAName()
+        internal static string FormatTagHelpers_AttributesMustHaveAName(object p0)
         {
-            return GetString("TagHelpers_AttributesMustHaveAName");
+            return string.Format(CultureInfo.CurrentCulture, GetString("TagHelpers_AttributesMustHaveAName"), p0);
         }
 
         /// <summary>
-        /// Tag Helpers cannot have C# in an HTML tag element's attribute declaration area.
+        /// The tag helper '{0}' must not have C# in the element's attribute declaration area.
         /// </summary>
         internal static string TagHelpers_CannotHaveCSharpInTagDeclaration
         {
@@ -1455,11 +1359,11 @@ namespace Microsoft.AspNet.Razor
         }
 
         /// <summary>
-        /// Tag Helpers cannot have C# in an HTML tag element's attribute declaration area.
+        /// The tag helper '{0}' must not have C# in the element's attribute declaration area.
         /// </summary>
-        internal static string FormatTagHelpers_CannotHaveCSharpInTagDeclaration()
+        internal static string FormatTagHelpers_CannotHaveCSharpInTagDeclaration(object p0)
         {
-            return GetString("TagHelpers_CannotHaveCSharpInTagDeclaration");
+            return string.Format(CultureInfo.CurrentCulture, GetString("TagHelpers_CannotHaveCSharpInTagDeclaration"), p0);
         }
 
         /// <summary>
@@ -1478,22 +1382,6 @@ namespace Microsoft.AspNet.Razor
             return GetString("TagHelpers_TagHelperCodeGeneartorMustBeAssociatedWithATagHelperBlock");
         }
 
-        /// <summary>
-        /// TagHelper attributes that do not expect strings must not have @ symbols within them. Found attribute '{0}' with an invalid value.
-        /// </summary>
-        internal static string TagHelpers_AttributesThatAreNotStringsMustNotContainAtSymbols
-        {
-            get { return GetString("TagHelpers_AttributesThatAreNotStringsMustNotContainAtSymbols"); }
-        }
-
-        /// <summary>
-        /// TagHelper attributes that do not expect strings must not have @ symbols within them. Found attribute '{0}' with an invalid value.
-        /// </summary>
-        internal static string FormatTagHelpers_AttributesThatAreNotStringsMustNotContainAtSymbols(object p0)
-        {
-            return string.Format(CultureInfo.CurrentCulture, GetString("TagHelpers_AttributesThatAreNotStringsMustNotContainAtSymbols"), p0);
-        }
-
         /// <summary>
         /// Directive '{0}' must have a value.
         /// </summary>
@@ -1542,6 +1430,106 @@ namespace Microsoft.AspNet.Razor
             return string.Format(CultureInfo.CurrentCulture, GetString("TagHelpersParseTreeRewriter_FoundMalformedTagHelper"), p0);
         }
 
+        /// <summary>
+        /// Missing close angle for tag helper '{0}'.
+        /// </summary>
+        internal static string TagHelpersParseTreeRewriter_MissingCloseAngle
+        {
+            get { return GetString("TagHelpersParseTreeRewriter_MissingCloseAngle"); }
+        }
+
+        /// <summary>
+        /// Missing close angle for tag helper '{0}'.
+        /// </summary>
+        internal static string FormatTagHelpersParseTreeRewriter_MissingCloseAngle(object p0)
+        {
+            return string.Format(CultureInfo.CurrentCulture, GetString("TagHelpersParseTreeRewriter_MissingCloseAngle"), p0);
+        }
+
+        /// <summary>
+        /// TagHelper attributes must be welformed.
+        /// </summary>
+        internal static string TagHelperBlockRewriter_TagHelperAttributesMustBeWelformed
+        {
+            get { return GetString("TagHelperBlockRewriter_TagHelperAttributesMustBeWelformed"); }
+        }
+
+        /// <summary>
+        /// TagHelper attributes must be welformed.
+        /// </summary>
+        internal static string FormatTagHelperBlockRewriter_TagHelperAttributesMustBeWelformed()
+        {
+            return GetString("TagHelperBlockRewriter_TagHelperAttributesMustBeWelformed");
+        }
+
+        /// <summary>
+        /// Non-string tag helper attribute values must not be empty. Add an expression to this attribute value.
+        /// </summary>
+        internal static string TagHelpers_AttributeExpressionRequired
+        {
+            get { return GetString("TagHelpers_AttributeExpressionRequired"); }
+        }
+
+        /// <summary>
+        /// Non-string tag helper attribute values must not be empty. Add an expression to this attribute value.
+        /// </summary>
+        internal static string FormatTagHelpers_AttributeExpressionRequired()
+        {
+            return GetString("TagHelpers_AttributeExpressionRequired");
+        }
+
+        /// <summary>
+        /// Code blocks (e.g. @{{var variable = 23;}}) must not appear in non-string tag helper attribute values.
+        ///  Already in an expression (code) context. If necessary an explicit expression (e.g. @(@readonly)) may be used.
+        /// </summary>
+        internal static string TagHelpers_CodeBlocks_NotSupported_InAttributes
+        {
+            get { return GetString("TagHelpers_CodeBlocks_NotSupported_InAttributes"); }
+        }
+
+        /// <summary>
+        /// Code blocks (e.g. @{{var variable = 23;}}) must not appear in non-string tag helper attribute values.
+        ///  Already in an expression (code) context. If necessary an explicit expression (e.g. @(@readonly)) may be used.
+        /// </summary>
+        internal static string FormatTagHelpers_CodeBlocks_NotSupported_InAttributes()
+        {
+            return GetString("TagHelpers_CodeBlocks_NotSupported_InAttributes");
+        }
+
+        /// <summary>
+        /// @'{0}' directives must not appear in non-string tag helper attribute values.
+        /// </summary>
+        internal static string TagHelpers_Directives_NotSupported_InAttributes
+        {
+            get { return GetString("TagHelpers_Directives_NotSupported_InAttributes"); }
+        }
+
+        /// <summary>
+        /// @'{0}' directives must not appear in non-string tag helper attribute values.
+        /// </summary>
+        internal static string FormatTagHelpers_Directives_NotSupported_InAttributes(object p0)
+        {
+            return string.Format(CultureInfo.CurrentCulture, GetString("TagHelpers_Directives_NotSupported_InAttributes"), p0);
+        }
+
+        /// <summary>
+        /// Inline markup blocks (e.g. @&lt;p&gt;content&lt;/p&gt;) must not appear in non-string tag helper attribute values.
+        ///  Expected a '{0}' attribute value, not a string.
+        /// </summary>
+        internal static string TagHelpers_InlineMarkupBlocks_NotSupported_InAttributes
+        {
+            get { return GetString("TagHelpers_InlineMarkupBlocks_NotSupported_InAttributes"); }
+        }
+
+        /// <summary>
+        /// Inline markup blocks (e.g. @&lt;p&gt;content&lt;/p&gt;) must not appear in non-string tag helper attribute values.
+        ///  Expected a '{0}' attribute value, not a string.
+        /// </summary>
+        internal static string FormatTagHelpers_InlineMarkupBlocks_NotSupported_InAttributes(object p0)
+        {
+            return string.Format(CultureInfo.CurrentCulture, GetString("TagHelpers_InlineMarkupBlocks_NotSupported_InAttributes"), p0);
+        }
+
         private static string GetString(string name, params string[] formatterNames)
         {
             var value = _resourceManager.GetString(name);

src/Microsoft.AspNet.Razor/RazorResources.resx

@@ -1,17 +1,17 @@
 <?xml version="1.0" encoding="utf-8"?>
 <root>
-  <!--
-    Microsoft ResX Schema
-
+  <!-- 
+    Microsoft ResX Schema 
+    
     Version 2.0
-
-    The primary goals of this format is to allow a simple XML format
-    that is mostly human readable. The generation and parsing of the
-    various data types are done through the TypeConverter classes
+    
+    The primary goals of this format is to allow a simple XML format 
+    that is mostly human readable. The generation and parsing of the 
+    various data types are done through the TypeConverter classes 
     associated with the data types.
-
+    
     Example:
-
+    
     ... ado.net/XML headers & schema ...
     <resheader name="resmimetype">text/microsoft-resx</resheader>
     <resheader name="version">2.0</resheader>
@@ -26,36 +26,36 @@
         <value>[base64 mime encoded string representing a byte array form of the .NET Framework object]</value>
         <comment>This is a comment</comment>
     </data>
-
-    There are any number of "resheader" rows that contain simple
+                
+    There are any number of "resheader" rows that contain simple 
     name/value pairs.
-
-    Each data row contains a name, and value. The row also contains a
-    type or mimetype. Type corresponds to a .NET class that support
-    text/value conversion through the TypeConverter architecture.
-    Classes that don't support this are serialized and stored with the
+    
+    Each data row contains a name, and value. The row also contains a 
+    type or mimetype. Type corresponds to a .NET class that support 
+    text/value conversion through the TypeConverter architecture. 
+    Classes that don't support this are serialized and stored with the 
     mimetype set.
-
-    The mimetype is used for serialized objects, and tells the
-    ResXResourceReader how to depersist the object. This is currently not
+    
+    The mimetype is used for serialized objects, and tells the 
+    ResXResourceReader how to depersist the object. This is currently not 
     extensible. For a given mimetype the value must be set accordingly:
-
-    Note - application/x-microsoft.net.object.binary.base64 is the format
-    that the ResXResourceWriter will generate, however the reader can
+    
+    Note - application/x-microsoft.net.object.binary.base64 is the format 
+    that the ResXResourceWriter will generate, however the reader can 
     read any of the formats listed below.
-
+    
     mimetype: application/x-microsoft.net.object.binary.base64
-    value   : The object must be serialized with
+    value   : The object must be serialized with 
             : System.Runtime.Serialization.Formatters.Binary.BinaryFormatter
             : and then encoded with base64 encoding.
-
+    
     mimetype: application/x-microsoft.net.object.soap.base64
-    value   : The object must be serialized with
+    value   : The object must be serialized with 
             : System.Runtime.Serialization.Formatters.Soap.SoapFormatter
             : and then encoded with base64 encoding.
 
     mimetype: application/x-microsoft.net.object.bytearray.base64
-    value   : The object must be serialized into a byte array
+    value   : The object must be serialized into a byte array 
             : using a System.ComponentModel.TypeConverter
             : and then encoded with base64 encoding.
     -->
@@ -206,12 +206,6 @@ Instead, wrap the contents of the block in "{{}}":
   <data name="ParseError_Unterminated_String_Literal" xml:space="preserve">
     <value>Unterminated string literal.  Strings that start with a quotation mark (") must be terminated before the end of the line.  However, strings that start with @ and a quotation mark (@") can span multiple lines.</value>
   </data>
-  <data name="ParseError_UnknownOption" xml:space="preserve">
-    <value>Unknown option: "{0}".</value>
-  </data>
-  <data name="ParseError_BlockNotTerminated" xml:space="preserve">
-    <value>The "{0}" block was not terminated.  All "{0}" statements must be terminated with a matching "{1}".</value>
-  </data>
   <data name="SectionExample_CS" xml:space="preserve">
     <value>@section Header { ... }</value>
     <comment>In CSHTML, the @section keyword is case-sensitive and lowercase (as with all C# keywords)</comment>
@@ -219,9 +213,6 @@ Instead, wrap the contents of the block in "{{}}":
   <data name="ParseError_TextTagCannotContainAttributes" xml:space="preserve">
     <value>"&lt;text&gt;" and "&lt;/text&gt;" tags cannot contain attributes.</value>
   </data>
-  <data name="ParseError_NamespaceOrTypeAliasExpected" xml:space="preserve">
-    <value>The "Imports" keyword must be followed by a namespace or a type alias on the same line.</value>
-  </data>
   <data name="ParseError_Unexpected_WhiteSpace_At_Start_Of_CodeBlock_CS" xml:space="preserve">
     <value>A space or line break was encountered after the "@" character.  Only valid identifiers, keywords, comments, "(" and "{" are valid at the start of a code block and they must occur immediately following "@" with no space in between.</value>
   </data>
@@ -321,9 +312,6 @@ Instead, wrap the contents of the block in "{{}}":
   <data name="TokenizerView_CannotPutBack" xml:space="preserve">
     <value>In order to put a symbol back, it must have been the symbol which ended at the current position. The specified symbol ends at {0}, but the current position is {1}</value>
   </data>
-  <data name="ParseError_Unexpected" xml:space="preserve">
-    <value>Unexpected "{0}"</value>
-  </data>
   <data name="ParseError_Unexpected_Nested_CodeBlock" xml:space="preserve">
     <value>Unexpected "{" after "@" character. Once inside the body of a code block (@if {}, @{}, etc.) you do not need to use "@{" to switch to code.</value>
   </data>
@@ -348,13 +336,6 @@ Instead, wrap the contents of the block in "{{}}":
   <data name="Language_Does_Not_Support_RazorComment" xml:space="preserve">
     <value>Cannot use built-in RazorComment handler, language characteristics does not define the CommentStart, CommentStar and CommentBody known symbol types or parser does not override TokenizerBackedParser.OutputSpanBeforeRazorComment</value>
   </data>
-  <data name="ParserEror_SessionDirectiveMissingValue" xml:space="preserve">
-    <value>Missing value for session state directive.</value>
-  </data>
-  <data name="CreateCodeWriter_NoCodeWriter" xml:space="preserve">
-    <value>Cannot call CreateCodeWriter, a CodeWriter was not provided to the Create method</value>
-    <comment>This error should not be seen by users, it should only appear to internal developers, but I'm putting it in resources just in case</comment>
-  </data>
   <data name="Trace_BackgroundThreadShutdown" xml:space="preserve">
     <value>[BG][{0}] Shutdown</value>
   </data>
@@ -404,17 +385,14 @@ Instead, wrap the contents of the block in "{{}}":
     <value>Section blocks ("{0}") cannot be nested.  Only one level of section blocks are allowed.</value>
   </data>
   <data name="TagHelpers_AttributesMustHaveAName" xml:space="preserve">
-    <value>Tag Helper attributes must have a name.</value>
+    <value>Tag Helper '{0}'s attributes must have names.</value>
   </data>
   <data name="TagHelpers_CannotHaveCSharpInTagDeclaration" xml:space="preserve">
-    <value>Tag Helpers cannot have C# in an HTML tag element's attribute declaration area.</value>
+    <value>The tag helper '{0}' must not have C# in the element's attribute declaration area.</value>
   </data>
   <data name="TagHelpers_TagHelperCodeGeneartorMustBeAssociatedWithATagHelperBlock" xml:space="preserve">
     <value>A TagHelperCodeGenerator must only be used with TagHelperBlocks.</value>
   </data>
-  <data name="TagHelpers_AttributesThatAreNotStringsMustNotContainAtSymbols" xml:space="preserve">
-    <value>TagHelper attributes that do not expect strings must not have @ symbols within them. Found attribute '{0}' with an invalid value.</value>
-  </data>
   <data name="ParseError_DirectiveMustHaveValue" xml:space="preserve">
     <value>Directive '{0}' must have a value.</value>
   </data>
@@ -424,4 +402,24 @@ Instead, wrap the contents of the block in "{{}}":
   <data name="TagHelpersParseTreeRewriter_FoundMalformedTagHelper" xml:space="preserve">
     <value>Found a malformed '{0}' tag helper. Tag helpers must have a start and end tag or be self closing.</value>
   </data>
+  <data name="TagHelpersParseTreeRewriter_MissingCloseAngle" xml:space="preserve">
+    <value>Missing close angle for tag helper '{0}'.</value>
+  </data>
+  <data name="TagHelperBlockRewriter_TagHelperAttributesMustBeWelformed" xml:space="preserve">
+    <value>TagHelper attributes must be welformed.</value>
+  </data>
+  <data name="TagHelpers_AttributeExpressionRequired" xml:space="preserve">
+    <value>Non-string tag helper attribute values must not be empty. Add an expression to this attribute value.</value>
+  </data>
+  <data name="TagHelpers_CodeBlocks_NotSupported_InAttributes" xml:space="preserve">
+    <value>Code blocks (e.g. @{{var variable = 23;}}) must not appear in non-string tag helper attribute values.
+ Already in an expression (code) context. If necessary an explicit expression (e.g. @(@readonly)) may be used.</value>
+  </data>
+  <data name="TagHelpers_Directives_NotSupported_InAttributes" xml:space="preserve">
+    <value>@'{0}' directives must not appear in non-string tag helper attribute values.</value>
+  </data>
+  <data name="TagHelpers_InlineMarkupBlocks_NotSupported_InAttributes" xml:space="preserve">
+    <value>Inline markup blocks (e.g. @&lt;p&gt;content&lt;/p&gt;) must not appear in non-string tag helper attribute values.
+ Expected a '{0}' attribute value, not a string.</value>
+  </data>
 </root>

src/Microsoft.AspNet.Razor/RazorTemplateEngine.cs

@@ -252,7 +252,7 @@ namespace Microsoft.AspNet.Razor
             generator.DesignTimeMode = Host.DesignTimeMode;
             generator.Visit(results);
 
-            var codeBuilderContext = new CodeBuilderContext(generator.Context);
+            var codeBuilderContext = new CodeBuilderContext(generator.Context, results.ErrorSink);
             codeBuilderContext.Checksum = checksum;
             var builder = CreateCodeBuilder(codeBuilderContext);
             var builderResult = builder.Build();

src/Microsoft.AspNet.Razor/TagHelpers/ContentBehavior.cs

@@ -1,43 +0,0 @@
-// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
-// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
-
-namespace Microsoft.AspNet.Razor.TagHelpers
-{
-    /// <summary>
-    /// Defines how a tag helper will utilize its inner HTML.
-    /// </summary>
-    public enum ContentBehavior
-    {
-        /// <summary>
-        /// Indicates that a tag helper will not modify its content in any way. This is the default
-        /// <see cref="ContentBehavior"/>.
-        /// </summary>
-        /// <remarks>Children of the current tag helper will execute after the current tag helper.</remarks>
-        None,
-
-        /// <summary>
-        /// Indicates the tag helper's content should be appended to what its children generate.
-        /// </summary>
-        /// <remarks>Children of the current tag helper will execute before the current tag helper.</remarks>
-        Append,
-
-        /// <summary>
-        /// Indicates that the tag helper will modify its HTML content. Therefore this <see cref="ContentBehavior"/>
-        /// enables the tag helper to examine the content its children generate.
-        /// </summary>
-        /// <remarks>Children of the current tag helper will execute before the current tag helper.</remarks>
-        Modify,
-
-        /// <summary>
-        /// Indicates the tag helper's content should be prepended to what its children generate.
-        /// </summary>
-        /// <remarks>Children of the current tag helper will execute after the current tag helper.</remarks>
-        Prepend,
-
-        /// <summary>
-        /// Indicates the tag helper's content should replace the HTML its children generate.
-        /// </summary>
-        /// <remarks>Children of the current tag helper will not execute.</remarks>
-        Replace,
-    }
-}

src/Microsoft.AspNet.Razor/TagHelpers/TagHelperAttributeValueCodeRenderer.cs

@@ -16,15 +16,25 @@ namespace Microsoft.AspNet.Razor.TagHelpers
         /// Called during Razor's code generation process to generate code that instantiates the value of the tag
         /// helper's property. Last value written should not be or end with a semicolon.
         /// </summary>
-        /// <param name="attributeDescriptor">The <see cref="TagHelperAttributeDescriptor"/> to generate code for.</param>
+        /// <param name="attributeDescriptor">
+        /// The <see cref="TagHelperAttributeDescriptor"/> to generate code for.
+        /// </param>
         /// <param name="writer">The <see cref="CSharpCodeWriter"/> that's used to write code.</param>
         /// <param name="context">A <see cref="CodeGeneratorContext"/> instance that contains information about
         /// the current code generation process.</param>
-        /// <param name="renderAttributeValue"><see cref="Action"/> that renders the raw value of the HTML attribute.</param>
+        /// <param name="renderAttributeValue">
+        /// <see cref="Action"/> that renders the raw value of the HTML attribute.
+        /// </param>
+        /// <param name="complexValue">
+        /// Indicates whether or not the source attribute value contains more than simple text. <c>false</c> for plain
+        /// C# expressions e.g. <c>"PropertyName"</c>. <c>true</c> if the attribute value contain at least one in-line
+        /// Razor construct e.g. <c>"@(@readonly)"</c>.
+        /// </param>
         public virtual void RenderAttributeValue([NotNull] TagHelperAttributeDescriptor attributeDescriptor,
                                                  [NotNull] CSharpCodeWriter writer,
                                                  [NotNull] CodeBuilderContext context,
-                                                 [NotNull] Action<CSharpCodeWriter> renderAttributeValue)
+                                                 [NotNull] Action<CSharpCodeWriter> renderAttributeValue,
+                                                 bool complexValue)
         {
             renderAttributeValue(writer);
         }

src/Microsoft.AspNet.Razor/TagHelpers/TagHelperDescriptor.cs

@@ -16,12 +16,10 @@ namespace Microsoft.AspNet.Razor.TagHelpers
         /// </summary>
         internal TagHelperDescriptor([NotNull] string tagName,
                                      [NotNull] string typeName,
-                                     [NotNull] string assemblyName,
-                                     ContentBehavior contentBehavior)
+                                     [NotNull] string assemblyName)
             : this(tagName,
                    typeName,
                    assemblyName,
-                   contentBehavior,
                    Enumerable.Empty<TagHelperAttributeDescriptor>())
         {
         }
@@ -34,21 +32,17 @@ namespace Microsoft.AspNet.Razor.TagHelpers
         /// <see cref="TagHelperDescriptor"/> which applies to every HTML tag.</param>
         /// <param name="typeName">The full name of the tag helper class.</param>
         /// <param name="assemblyName">The name of the assembly containing the tag helper class.</param>
-        /// <param name="contentBehavior">The <see cref="TagHelpers.ContentBehavior"/>
-        /// of the tag helper.</param>
         /// <param name="attributes">
         /// The <see cref="TagHelperAttributeDescriptor"/>s to request from the HTML tag.
         /// </param>
         public TagHelperDescriptor([NotNull] string tagName,
                                    [NotNull] string typeName,
                                    [NotNull] string assemblyName,
-                                   ContentBehavior contentBehavior,
                                    [NotNull] IEnumerable<TagHelperAttributeDescriptor> attributes)
         {
             TagName = tagName;
             TypeName = typeName;
             AssemblyName = assemblyName;
-            ContentBehavior = contentBehavior;
             Attributes = new List<TagHelperAttributeDescriptor>(attributes);
         }
 
@@ -67,11 +61,6 @@ namespace Microsoft.AspNet.Razor.TagHelpers
         /// </summary>
         public string AssemblyName { get; private set; }
 
-        /// <summary>
-        /// The <see cref="TagHelpers.ContentBehavior"/> of the tag helper.
-        /// </summary>
-        public ContentBehavior ContentBehavior { get; private set; }
-
         /// <summary>
         /// The list of attributes the tag helper expects.
         /// </summary>

src/Microsoft.AspNet.Razor/TagHelpers/TagHelperDescriptorComparer.cs

@@ -29,15 +29,13 @@ namespace Microsoft.AspNet.Razor.TagHelpers
         /// <c>false</c> otherwise.</returns>
         /// <remarks>
         /// Determines equality based on <see cref="TagHelperDescriptor.TypeName"/>,
-        /// <see cref="TagHelperDescriptor.AssemblyName"/>, <see cref="TagHelperDescriptor.TagName"/> and
-        /// <see cref="TagHelperDescriptor.ContentBehavior"/>.
+        /// <see cref="TagHelperDescriptor.AssemblyName"/> and <see cref="TagHelperDescriptor.TagName"/>.
         /// </remarks>
         public bool Equals(TagHelperDescriptor descriptorX, TagHelperDescriptor descriptorY)
         {
             return string.Equals(descriptorX.TypeName, descriptorY.TypeName, StringComparison.Ordinal) &&
                    string.Equals(descriptorX.TagName, descriptorY.TagName, StringComparison.OrdinalIgnoreCase) &&
-                   string.Equals(descriptorX.AssemblyName, descriptorY.AssemblyName, StringComparison.Ordinal) &&
-                   descriptorX.ContentBehavior == descriptorY.ContentBehavior;
+                   string.Equals(descriptorX.AssemblyName, descriptorY.AssemblyName, StringComparison.Ordinal);
         }
 
         /// <summary>
@@ -51,7 +49,6 @@ namespace Microsoft.AspNet.Razor.TagHelpers
                                    .Add(descriptor.TagName, StringComparer.OrdinalIgnoreCase)
                                    .Add(descriptor.TypeName, StringComparer.Ordinal)
                                    .Add(descriptor.AssemblyName, StringComparer.Ordinal)
-                                   .Add(descriptor.ContentBehavior)
                                    .CombinedHash;
         }
     }

src/Microsoft.AspNet.Razor/project.json

@@ -9,12 +9,13 @@
                 "System.Collections": "4.0.10-beta-*",
                 "System.Diagnostics.Debug": "4.0.10-beta-*",
                 "System.Diagnostics.Tools": "4.0.0-beta-*",
+                "System.IO": "4.0.10-beta-*",
                 "System.IO.FileSystem": "4.0.0-beta-*",
                 "System.Linq": "4.0.0-beta-*",
                 "System.Reflection": "4.0.10-beta-*",
                 "System.Resources.ResourceManager": "4.0.0-beta-*",
                 "System.Runtime.Extensions": "4.0.10-beta-*",
-                "System.Threading": "4.0.0-beta-*",
+                "System.Threading": "4.0.10-beta-*",
                 "System.Threading.Tasks": "4.0.10-beta-*",
                 "System.Threading.Thread": "4.0.0-beta-*",
                 "System.Security.Cryptography.Hashing.Algorithms": "4.0.0-beta-*"

test/Microsoft.AspNet.Razor.Runtime.Test/TagHelpers/CompleteTagHelperDescriptorComparer.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using Microsoft.AspNet.Razor.TagHelpers;
@@ -20,6 +21,8 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
         bool IEqualityComparer<TagHelperDescriptor>.Equals(TagHelperDescriptor descriptorX, TagHelperDescriptor descriptorY)
         {
             return base.Equals(descriptorX, descriptorY) &&
+                   // Tests should be exact casing
+                   string.Equals(descriptorX.TagName, descriptorY.TagName, StringComparison.Ordinal) &&
                    descriptorX.Attributes.SequenceEqual(descriptorY.Attributes,
                                                         CompleteTagHelperAttributeDescriptorComparer.Default);
         }
@@ -43,17 +46,17 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
 
             public bool Equals(TagHelperAttributeDescriptor descriptorX, TagHelperAttributeDescriptor descriptorY)
             {
-                return descriptorX.Name == descriptorY.Name &&
-                       descriptorX.PropertyName == descriptorY.PropertyName &&
-                       descriptorX.TypeName == descriptorY.TypeName;
+                return string.Equals(descriptorX.Name, descriptorY.Name, StringComparison.Ordinal) &&
+                       string.Equals(descriptorX.PropertyName, descriptorY.PropertyName, StringComparison.Ordinal) &&
+                       string.Equals(descriptorX.TypeName, descriptorY.TypeName, StringComparison.Ordinal);
             }
 
             public int GetHashCode(TagHelperAttributeDescriptor descriptor)
             {
                 return HashCodeCombiner.Start()
-                                       .Add(descriptor.Name)
-                                       .Add(descriptor.PropertyName)
-                                       .Add(descriptor.TypeName)
+                                       .Add(descriptor.Name, StringComparer.Ordinal)
+                                       .Add(descriptor.PropertyName, StringComparer.Ordinal)
+                                       .Add(descriptor.TypeName, StringComparer.Ordinal)
                                        .CombinedHash;
             }
         }

test/Microsoft.AspNet.Razor.Runtime.Test/TagHelpers/TagHelperDescriptorFactoryTest.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using System.Reflection;
 using Microsoft.AspNet.Razor.TagHelpers;
 using Xunit;
@@ -12,6 +13,42 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
         private static readonly string AssemblyName =
             typeof(TagHelperDescriptorFactoryTest).GetTypeInfo().Assembly.GetName().Name;
 
+        public static TheoryData HtmlCaseData
+        {
+            get
+            {
+                // tagHelperType, expectedTagName, expectedAttributeName
+                return new TheoryData<Type, string, string>
+                {
+                    { typeof(SingleAttributeTagHelper), "single-attribute", "int-attribute" },
+                    { typeof(ALLCAPSTAGHELPER), "allcaps", "allcapsattribute" },
+                    { typeof(CAPSOnOUTSIDETagHelper), "caps-on-outside", "caps-on-outsideattribute" },
+                    { typeof(capsONInsideTagHelper), "caps-on-inside", "caps-on-insideattribute" },
+                    { typeof(One1Two2Three3TagHelper), "one1-two2-three3", "one1-two2-three3-attribute" },
+                    { typeof(ONE1TWO2THREE3TagHelper), "one1two2three3", "one1two2three3-attribute" },
+                    { typeof(First_Second_ThirdHiTagHelper), "first_second_third-hi", "first_second_third-attribute" },
+                    { typeof(UNSuffixedCLASS), "un-suffixed-class", "un-suffixed-attribute" },
+                };
+            }
+        }
+
+        [Theory]
+        [MemberData(nameof(HtmlCaseData))]
+        public void CreateDescriptor_HtmlCasesTagNameAndAttributeName(
+            Type tagHelperType,
+            string expectedTagName,
+            string expectedAttributeName)
+        {
+            // Arrange & Act
+            var descriptors = TagHelperDescriptorFactory.CreateDescriptors(tagHelperType);
+
+            // Assert
+            var descriptor = Assert.Single(descriptors);
+            Assert.Equal(expectedTagName, descriptor.TagName, StringComparer.Ordinal);
+            var attributeDescriptor = Assert.Single(descriptor.Attributes);
+            Assert.Equal(expectedAttributeName, attributeDescriptor.Name);
+        }
+
         [Fact]
         public void CreateDescriptor_OverridesAttributeNameFromAttribute()
         {
@@ -22,10 +59,9 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
                 nameof(OverriddenAttributeTagHelper.ValidAttribute2));
             var expectedDescriptors = new[] {
                 new TagHelperDescriptor(
-                    "OverriddenAttribute",
+                    "overridden-attribute",
                     typeof(OverriddenAttributeTagHelper).FullName,
                     AssemblyName,
-                    ContentBehavior.None,
                     new[] {
                         new TagHelperAttributeDescriptor("SomethingElse", validProperty1),
                         new TagHelperAttributeDescriptor("Something-Else", validProperty2)
@@ -49,12 +85,11 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
                 nameof(InheritedOverriddenAttributeTagHelper.ValidAttribute2));
             var expectedDescriptors = new[] {
                 new TagHelperDescriptor(
-                    "InheritedOverriddenAttribute",
+                    "inherited-overridden-attribute",
                     typeof(InheritedOverriddenAttributeTagHelper).FullName,
                     AssemblyName,
-                    ContentBehavior.None,
                     new[] {
-                        new TagHelperAttributeDescriptor(nameof(InheritedOverriddenAttributeTagHelper.ValidAttribute1),
+                        new TagHelperAttributeDescriptor("valid-attribute1",
                                                          validProperty1),
                         new TagHelperAttributeDescriptor("Something-Else", validProperty2)
                     })
@@ -77,10 +112,9 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
                 nameof(InheritedNotOverriddenAttributeTagHelper.ValidAttribute2));
             var expectedDescriptors = new[] {
                 new TagHelperDescriptor(
-                    "InheritedNotOverriddenAttribute",
+                    "inherited-not-overridden-attribute",
                     typeof(InheritedNotOverriddenAttributeTagHelper).FullName,
                     AssemblyName,
-                    ContentBehavior.None,
                     new[] {
                         new TagHelperAttributeDescriptor("SomethingElse", validProperty1),
                         new TagHelperAttributeDescriptor("Something-Else", validProperty2)
@@ -100,7 +134,7 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             // Arrange
             var objectAssemblyName = typeof(object).GetTypeInfo().Assembly.GetName().Name;
             var expectedDescriptor =
-                new TagHelperDescriptor("Object", "System.Object", objectAssemblyName, ContentBehavior.None);
+                new TagHelperDescriptor("object", "System.Object", objectAssemblyName);
 
             // Act
             var descriptors = TagHelperDescriptorFactory.CreateDescriptors(typeof(object));
@@ -117,12 +151,11 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             var intProperty = typeof(InheritedSingleAttributeTagHelper).GetProperty(
                 nameof(InheritedSingleAttributeTagHelper.IntAttribute));
             var expectedDescriptor = new TagHelperDescriptor(
-                "InheritedSingleAttribute",
+                "inherited-single-attribute",
                 typeof(InheritedSingleAttributeTagHelper).FullName,
                 AssemblyName,
-                ContentBehavior.None,
                 new[] {
-                    new TagHelperAttributeDescriptor(nameof(InheritedSingleAttributeTagHelper.IntAttribute), intProperty)
+                    new TagHelperAttributeDescriptor("int-attribute", intProperty)
                 });
 
             // Act
@@ -139,12 +172,11 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             // Arrange
             var intProperty = typeof(SingleAttributeTagHelper).GetProperty(nameof(SingleAttributeTagHelper.IntAttribute));
             var expectedDescriptor = new TagHelperDescriptor(
-                "SingleAttribute",
+                "single-attribute",
                 typeof(SingleAttributeTagHelper).FullName,
                 AssemblyName,
-                ContentBehavior.None,
                 new[] {
-                    new TagHelperAttributeDescriptor(nameof(SingleAttributeTagHelper.IntAttribute), intProperty)
+                    new TagHelperAttributeDescriptor("int-attribute", intProperty)
                 });
 
             // Act
@@ -162,12 +194,11 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             var validProperty = typeof(MissingAccessorTagHelper).GetProperty(
                 nameof(MissingAccessorTagHelper.ValidAttribute));
             var expectedDescriptor = new TagHelperDescriptor(
-                "MissingAccessor",
+                "missing-accessor",
                 typeof(MissingAccessorTagHelper).FullName,
                 AssemblyName,
-                ContentBehavior.None,
                 new[] {
-                    new TagHelperAttributeDescriptor(nameof(MissingAccessorTagHelper.ValidAttribute), validProperty)
+                    new TagHelperAttributeDescriptor("valid-attribute", validProperty)
                 });
 
             // Act
@@ -185,13 +216,12 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             var validProperty = typeof(PrivateAccessorTagHelper).GetProperty(
                 nameof(PrivateAccessorTagHelper.ValidAttribute));
             var expectedDescriptor = new TagHelperDescriptor(
-                "PrivateAccessor",
+                "private-accessor",
                 typeof(PrivateAccessorTagHelper).FullName,
                 AssemblyName,
-                ContentBehavior.None,
                 new[] {
                     new TagHelperAttributeDescriptor(
-                        nameof(PrivateAccessorTagHelper.ValidAttribute), validProperty)
+                        "valid-attribute", validProperty)
                 });
 
             // Act
@@ -202,43 +232,6 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             Assert.Equal(expectedDescriptor, descriptor, CompleteTagHelperDescriptorComparer.Default);
         }
 
-        [Fact]
-        public void CreateDescriptor_ResolvesCustomContentBehavior()
-        {
-            // Arrange
-            var expectedDescriptor = new TagHelperDescriptor(
-                "CustomContentBehavior",
-                typeof(CustomContentBehaviorTagHelper).FullName,
-                AssemblyName,
-                ContentBehavior.Append);
-
-            // Act
-            var descriptors = TagHelperDescriptorFactory.CreateDescriptors(typeof(CustomContentBehaviorTagHelper));
-
-            // Assert
-            var descriptor = Assert.Single(descriptors);
-            Assert.Equal(expectedDescriptor, descriptor, CompleteTagHelperDescriptorComparer.Default);
-        }
-
-        [Fact]
-        public void CreateDescriptor_DoesNotResolveInheritedCustomContentBehavior()
-        {
-            // Arrange
-            var expectedDescriptor = new TagHelperDescriptor(
-                "InheritedCustomContentBehavior",
-                typeof(InheritedCustomContentBehaviorTagHelper).FullName,
-                AssemblyName,
-                ContentBehavior.None);
-
-            // Act
-            var descriptors = TagHelperDescriptorFactory.CreateDescriptors(
-                typeof(InheritedCustomContentBehaviorTagHelper));
-
-            // Assert
-            var descriptor = Assert.Single(descriptors);
-            Assert.Equal(expectedDescriptor, descriptor, CompleteTagHelperDescriptorComparer.Default);
-        }
-
         [Fact]
         public void CreateDescriptor_ResolvesMultipleTagHelperDescriptorsFromSingleType()
         {
@@ -249,17 +242,15 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
                     "div",
                     typeof(MultiTagTagHelper).FullName,
                     AssemblyName,
-                    ContentBehavior.None,
                     new[] {
-                        new TagHelperAttributeDescriptor(nameof(MultiTagTagHelper.ValidAttribute), validProp)
+                        new TagHelperAttributeDescriptor("valid-attribute", validProp)
                     }),
                 new TagHelperDescriptor(
                     "p",
                     typeof(MultiTagTagHelper).FullName,
                     AssemblyName,
-                    ContentBehavior.None,
                     new[] {
-                        new TagHelperAttributeDescriptor(nameof(MultiTagTagHelper.ValidAttribute), validProp)
+                        new TagHelperAttributeDescriptor("valid-attribute", validProp)
                     })
             };
 
@@ -276,12 +267,11 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             // Arrange
             var validProp = typeof(InheritedMultiTagTagHelper).GetProperty(nameof(InheritedMultiTagTagHelper.ValidAttribute));
             var expectedDescriptor = new TagHelperDescriptor(
-                    "InheritedMultiTag",
+                    "inherited-multi-tag",
                     typeof(InheritedMultiTagTagHelper).FullName,
                     AssemblyName,
-                    ContentBehavior.None,
                     new[] {
-                        new TagHelperAttributeDescriptor(nameof(InheritedMultiTagTagHelper.ValidAttribute), validProp)
+                        new TagHelperAttributeDescriptor("valid-attribute", validProp)
                     });
 
             // Act
@@ -300,13 +290,11 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
                 new TagHelperDescriptor(
                     "p",
                     typeof(DuplicateTagNameTagHelper).FullName,
-                    AssemblyName,
-                    ContentBehavior.None),
+                    AssemblyName),
                 new TagHelperDescriptor(
                     "div",
                     typeof(DuplicateTagNameTagHelper).FullName,
-                    AssemblyName,
-                    ContentBehavior.None)
+                    AssemblyName)
             };
 
             // Act
@@ -323,8 +311,7 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             var expectedDescriptors = new[] {
                 new TagHelperDescriptor("data-condition",
                                         typeof(OverrideNameTagHelper).FullName,
-                                        AssemblyName,
-                                        ContentBehavior.None),
+                                        AssemblyName),
             };
 
             // Act
@@ -342,18 +329,15 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
                 new TagHelperDescriptor(
                     "span",
                     typeof(MultipleAttributeTagHelper).FullName,
-                    AssemblyName,
-                    ContentBehavior.None),
+                    AssemblyName),
                 new TagHelperDescriptor(
                     "p",
                     typeof(MultipleAttributeTagHelper).FullName,
-                    AssemblyName,
-                    ContentBehavior.None),
+                    AssemblyName),
                 new TagHelperDescriptor(
                     "div",
                     typeof(MultipleAttributeTagHelper).FullName,
-                    AssemblyName,
-                    ContentBehavior.None)
+                    AssemblyName)
             };
 
             // Act
@@ -363,16 +347,7 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             Assert.Equal(expectedDescriptors, descriptors, CompleteTagHelperDescriptorComparer.Default);
         }
 
-        [ContentBehavior(ContentBehavior.Append)]
-        private class CustomContentBehaviorTagHelper
-        {
-        }
-
-        private class InheritedCustomContentBehaviorTagHelper : CustomContentBehaviorTagHelper
-        {
-        }
-
-        [TagName("p", "div")]
+        [HtmlElementName("p", "div")]
         private class MultiTagTagHelper
         {
             public string ValidAttribute { get; set; }
@@ -382,18 +357,18 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
         {
         }
 
-        [TagName("p", "p", "div", "div")]
+        [HtmlElementName("p", "p", "div", "div")]
         private class DuplicateTagNameTagHelper
         {
         }
 
-        [TagName("data-condition")]
+        [HtmlElementName("data-condition")]
         private class OverrideNameTagHelper
         {
         }
 
-        [TagName("span")]
-        [TagName("div", "p")]
+        [HtmlElementName("span")]
+        [HtmlElementName("div", "p")]
         private class MultipleAttributeTagHelper
         {
         }
@@ -419,5 +394,41 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
         private class InheritedNotOverriddenAttributeTagHelper : OverriddenAttributeTagHelper
         {
         }
+
+        private class ALLCAPSTAGHELPER : TagHelper
+        {
+            public int ALLCAPSATTRIBUTE { get; set; }
+        }
+
+        private class CAPSOnOUTSIDETagHelper : TagHelper
+        {
+            public int CAPSOnOUTSIDEATTRIBUTE { get; set; }
+        }
+
+        private class capsONInsideTagHelper : TagHelper
+        {
+            public int capsONInsideattribute { get; set; }
+        }
+
+        private class One1Two2Three3TagHelper : TagHelper
+        {
+            public int One1Two2Three3Attribute { get; set; }
+        }
+
+        private class ONE1TWO2THREE3TagHelper : TagHelper
+        {
+            public int ONE1TWO2THREE3Attribute { get; set; }
+        }
+
+        private class First_Second_ThirdHiTagHelper : TagHelper
+        {
+            public int First_Second_ThirdAttribute { get; set; }
+        }
+
+        private class UNSuffixedCLASS : TagHelper
+        {
+            public int UNSuffixedATTRIBUTE { get; set; }
+
+        }
     }
 }

test/Microsoft.AspNet.Razor.Runtime.Test/TagHelpers/TagHelperDescriptorResolverTest.cs

@@ -25,10 +25,9 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
         {
             get
             {
-                return new TagHelperDescriptor("Valid_Plain",
+                return new TagHelperDescriptor("valid_plain",
                                                Valid_PlainTagHelperType.FullName,
-                                               AssemblyName,
-                                               ContentBehavior.None);
+                                               AssemblyName);
             }
         }
 
@@ -36,10 +35,9 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
         {
             get
             {
-                return new TagHelperDescriptor("Valid_Inherited",
+                return new TagHelperDescriptor("valid_inherited",
                                                Valid_InheritedTagHelperType.FullName,
-                                               AssemblyName,
-                                               ContentBehavior.None);
+                                               AssemblyName);
             }
         }
 
@@ -75,8 +73,7 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
                 var stringTagHelperDescriptor =
                     new TagHelperDescriptor("string",
                                             "System.String",
-                                            assemblyB,
-                                            ContentBehavior.None);
+                                            assemblyB);
 
                 return new TheoryData<Dictionary<string, IEnumerable<Type>>, // descriptorAssemblyLookups
                                       IEnumerable<TagHelperDirectiveDescriptor>, // directiveDescriptors
@@ -230,8 +227,7 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
                 var stringTagHelperDescriptor =
                     new TagHelperDescriptor("string",
                                             "System.String",
-                                            assemblyB,
-                                            ContentBehavior.None);
+                                            assemblyB);
 
                 return new TheoryData<Dictionary<string, IEnumerable<Type>>, // descriptorAssemblyLookups
                                       IEnumerable<TagHelperDirectiveDescriptor>> // directiveDescriptors
@@ -358,7 +354,7 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             // Arrange
             var tagHelperTypeResolver = new TestTagHelperTypeResolver(TestableTagHelpers)
             {
-                OnGetLibraryDefinedTypes = (assemblyName) =>
+                OnGetExportedTypes = (assemblyName) =>
                 {
                     Assert.Equal("MyAssembly", assemblyName.Name);
                 }
@@ -523,7 +519,7 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
                 _lookupValues = lookupValues;
             }
 
-            internal override IEnumerable<TypeInfo> GetLibraryDefinedTypes(AssemblyName assemblyName)
+            protected override IEnumerable<TypeInfo> GetExportedTypes(AssemblyName assemblyName)
             {
                 IEnumerable<Type> types;
 

test/Microsoft.AspNet.Razor.Runtime.Test/TagHelpers/TagHelperExecutionContextTest.cs

@@ -1,14 +1,76 @@
 // Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
+using System.Threading.Tasks;
 using Xunit;
 
 namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
 {
     public class TagHelperExecutionContextTest
     {
+        [Fact]
+        public async Task GetChildContentAsync_CachesValue()
+        {
+            // Arrange
+            var writer = new StringWriter();
+            var expectedContent = string.Empty;
+            var executionContext = new TagHelperExecutionContext(
+                "p",
+                uniqueId: string.Empty,
+                executeChildContentAsync: () =>
+                {
+                    if (string.IsNullOrEmpty(expectedContent))
+                    {
+                        expectedContent = "Hello from child content: " + Guid.NewGuid().ToString();
+                    }
+
+                    writer.Write(expectedContent);
+
+                    return Task.FromResult(result: true);
+                },
+                startWritingScope: () => { },
+                endWritingScope: () => writer);
+
+            // Act
+            var content1 = await executionContext.GetChildContentAsync();
+            var content2 = await executionContext.GetChildContentAsync();
+
+            // Assert
+            Assert.Same(content1, content2);
+            Assert.Equal(expectedContent, content1);
+            Assert.Equal(expectedContent, content2);
+        }
+
+        [Fact]
+        public async Task ExecuteChildContentAsync_IsNotMemoized()
+        {
+            // Arrange
+            var childContentExecutionCount = 0;
+            var executionContext = new TagHelperExecutionContext(
+                "p",
+                uniqueId: string.Empty,
+                executeChildContentAsync: () =>
+                {
+                    childContentExecutionCount++;
+
+                    return Task.FromResult(result: true);
+                },
+                startWritingScope: () => { },
+                endWritingScope: () => new StringWriter());
+
+            // Act
+            await executionContext.ExecuteChildContentAsync();
+            await executionContext.ExecuteChildContentAsync();
+            await executionContext.ExecuteChildContentAsync();
+
+            // Assert
+            Assert.Equal(3, childContentExecutionCount);
+        }
+
         public static TheoryData<string, string> DictionaryCaseTestingData
         {
             get

test/Microsoft.AspNet.Razor.Runtime.Test/TagHelpers/TagHelperOutputTest.cs

@@ -9,39 +9,65 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
     public class TagHelperOutputTest
     {
         [Fact]
-        public void TagName_CannotSetToNullInCtor()
+        public void TagName_CanSetToNullInCtor()
         {
             // Arrange & Act
             var tagHelperOutput = new TagHelperOutput(null);
 
             // Assert
-            Assert.Empty(tagHelperOutput.TagName);
+            Assert.Null(tagHelperOutput.TagName);
         }
 
         [Fact]
-        public void TagName_CannotSetToNull()
+        public void TagName_CanSetToNull()
         {
-            // Arrange
-            var tagHelperOutput = new TagHelperOutput("p");
-
-            // Act
-            tagHelperOutput.TagName = null;
+            // Arrange & Act
+            var tagHelperOutput = new TagHelperOutput("p")
+            {
+                TagName = null
+            };
 
             // Assert
-            Assert.Empty(tagHelperOutput.TagName);
+            Assert.Null(tagHelperOutput.TagName);
         }
 
         [Fact]
-        public void Content_CannotSetToNull()
+        public void Content_CanSetToNull()
         {
-            // Arrange
-            var tagHelperOutput = new TagHelperOutput("p");
-
-            // Act
-            tagHelperOutput.Content = null;
+            // Arrange & Act
+            var tagHelperOutput = new TagHelperOutput("p")
+            {
+                Content = null
+            };
 
             // Assert
-            Assert.Empty(tagHelperOutput.Content);
+            Assert.Null(tagHelperOutput.Content);
+        }
+
+        [Fact]
+        public void PreContent_CanSetToNull()
+        {
+            // Arrange & Act
+            var tagHelperOutput = new TagHelperOutput("p")
+            {
+                PreContent = null
+            };
+
+            // Assert
+            Assert.Null(tagHelperOutput.PreContent);
+        }
+
+        [Fact]
+        public void PostContent_CanSetToNull()
+        {
+            // Arrange & Act
+            var tagHelperOutput = new TagHelperOutput("p")
+            {
+                PostContent = null
+            };
+
+            // Assert
+            Assert.Null(tagHelperOutput.PostContent);
         }
 
         [Fact]
@@ -119,9 +145,10 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
                 {
                     { "class", "btn" },
                     { "something", "   spaced    " }
-                });
-
-            tagHelperOutput.SelfClosing = true;
+                })
+            {
+                SelfClosing = true
+            };
 
             // Act
             var output = tagHelperOutput.GenerateStartTag();
@@ -135,9 +162,10 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
         public void GenerateEndTag_ReturnsNothingIfWhitespaceTagName()
         {
             // Arrange
-            var tagHelperOutput = new TagHelperOutput(" "); ;
-
-            tagHelperOutput.Content = "Hello World";
+            var tagHelperOutput = new TagHelperOutput(" ")
+            {
+                Content = "Hello World"
+            };
 
             // Act
             var output = tagHelperOutput.GenerateEndTag();
@@ -146,13 +174,47 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             Assert.Empty(output);
         }
 
+        [Fact]
+        public void GeneratePreContent_ReturnsPreContent()
+        {
+            // Arrange
+            var tagHelperOutput = new TagHelperOutput("p")
+            {
+                PreContent = "Hello World"
+            };
+
+            // Act
+            var output = tagHelperOutput.GeneratePreContent();
+
+            // Assert
+            Assert.Equal("Hello World", output);
+        }
+
+        [Fact]
+        public void GeneratePreContent_ReturnsNothingIfSelfClosing()
+        {
+            // Arrange
+            var tagHelperOutput = new TagHelperOutput("p")
+            {
+                SelfClosing = true,
+                PreContent = "Hello World"
+            };
+
+            // Act
+            var output = tagHelperOutput.GeneratePreContent();
+
+            // Assert
+            Assert.Empty(output);
+        }
+
         [Fact]
         public void GenerateContent_ReturnsContent()
         {
             // Arrange
-            var tagHelperOutput = new TagHelperOutput("p");
-
-            tagHelperOutput.Content = "Hello World";
+            var tagHelperOutput = new TagHelperOutput("p")
+            {
+                Content = "Hello World"
+            };
 
             // Act
             var output = tagHelperOutput.GenerateContent();
@@ -168,11 +230,10 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             // Arrange
             var tagHelperOutput = new TagHelperOutput("p")
             {
-                SelfClosing = true
+                SelfClosing = true,
+                Content = "Hello World"
             };
 
-            tagHelperOutput.Content = "Hello World";
-
             // Act
             var output = tagHelperOutput.GenerateContent();
 
@@ -180,6 +241,39 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             Assert.Empty(output);
         }
 
+        [Fact]
+        public void GeneratePostContent_ReturnsPostContent()
+        {
+            // Arrange
+            var tagHelperOutput = new TagHelperOutput("p")
+            {
+                PostContent = "Hello World"
+            };
+
+            // Act
+            var output = tagHelperOutput.GeneratePostContent();
+
+            // Assert
+            Assert.Equal("Hello World", output);
+        }
+
+        [Fact]
+        public void GeneratePostContent_ReturnsNothingIfSelfClosing()
+        {
+            // Arrange
+            var tagHelperOutput = new TagHelperOutput("p")
+            {
+                SelfClosing = true,
+                PostContent = "Hello World"
+            };
+
+            // Act
+            var output = tagHelperOutput.GeneratePostContent();
+
+            // Assert
+            Assert.Empty(output);
+        }
+
         [Fact]
         public void GenerateEndTag_ReturnsEndTag()
         {
@@ -209,6 +303,54 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             Assert.Empty(output);
         }
 
+        [Fact]
+        public void SuppressOutput_Sets_TagName_Content_PreContent_PostContent_ToNull()
+        {
+            // Arrange
+            var tagHelperOutput = new TagHelperOutput("p")
+            {
+                PreContent = "Pre Content",
+                Content = "Content",
+                PostContent = "Post Content"
+            };
+
+            // Act
+            tagHelperOutput.SuppressOutput();
+
+            // Assert
+            Assert.Null(tagHelperOutput.TagName);
+            Assert.Null(tagHelperOutput.PreContent);
+            Assert.Null(tagHelperOutput.Content);
+            Assert.Null(tagHelperOutput.PostContent);
+        }
+
+        [Fact]
+        public void SuppressOutput_PreventsTagOutput()
+        {
+            // Arrange
+            var tagHelperOutput = new TagHelperOutput("p",
+                attributes: new Dictionary<string, string>
+                {
+                    { "class", "btn" },
+                    { "something", "   spaced    " }
+                })
+            {
+                PreContent = "Pre Content",
+                Content = "Content",
+                PostContent = "Post Content"
+            };
+
+            // Act
+            tagHelperOutput.SuppressOutput();
+
+            // Assert
+            Assert.Empty(tagHelperOutput.GenerateStartTag());
+            Assert.Null(tagHelperOutput.GeneratePreContent());
+            Assert.Null(tagHelperOutput.GenerateContent());
+            Assert.Null(tagHelperOutput.GeneratePostContent());
+            Assert.Empty(tagHelperOutput.GenerateEndTag());
+        }
+
         [Theory]
         [InlineData("class", "ClASs")]
         [InlineData("CLaSs", "class")]

test/Microsoft.AspNet.Razor.Runtime.Test/TagHelpers/TagHelperRunnerTest.cs

@@ -66,23 +66,6 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             Assert.Equal("True", output.Attributes["foo"]);
         }
 
-        [Fact]
-        public async Task RunAsync_WithContentSetsOutputsContent()
-        {
-            // Arrange
-            var runner = new TagHelperRunner();
-            var executionContext = new TagHelperExecutionContext("p");
-            var tagHelper = new ExecutableTagHelper();
-            var contentWriter = new StringWriter(new StringBuilder("Hello World"));
-
-            // Act
-            executionContext.Add(tagHelper);
-            var output = await runner.RunAsync(executionContext, contentWriter);
-
-            // Assert
-            Assert.Equal(output.Content, "Hello World");
-        }
-
         private class ExecutableTagHelper : TagHelper
         {
             public bool Processed { get; set; }

test/Microsoft.AspNet.Razor.Runtime.Test/TagHelpers/TagHelperScopeManagerTest.cs

@@ -2,6 +2,8 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.IO;
+using System.Threading.Tasks;
 using Microsoft.AspNet.Razor.Runtime.TagHelpers;
 using Xunit;
 
@@ -9,6 +11,11 @@ namespace Microsoft.AspNet.Razor.Runtime.Test.TagHelpers
 {
     public class TagHelperScopeManagerTest
     {
+        private static readonly Action DefaultStartWritingScope = () => { };
+        private static readonly Func<TextWriter> DefaultEndWritingScope = () => new StringWriter();
+        private static readonly Func<Task> DefaultExecuteChildContentAsync =
+            async () => await Task.FromResult(result: true);
+
         [Fact]
         public void Begin_CreatesContextWithAppropriateTagName()
         {
@@ -16,7 +23,11 @@ namespace Microsoft.AspNet.Razor.Runtime.Test.TagHelpers
             var scopeManager = new TagHelperScopeManager();
 
             // Act
-            var executionContext = scopeManager.Begin("p");
+            var executionContext = scopeManager.Begin("p",
+                                                      string.Empty,
+                                                      DefaultExecuteChildContentAsync,
+                                                      DefaultStartWritingScope,
+                                                      DefaultEndWritingScope);
 
             // Assert
             Assert.Equal("p", executionContext.TagName);
@@ -29,8 +40,16 @@ namespace Microsoft.AspNet.Razor.Runtime.Test.TagHelpers
             var scopeManager = new TagHelperScopeManager();
 
             // Act
-            var executionContext = scopeManager.Begin("p");
-            executionContext = scopeManager.Begin("div");
+            var executionContext = scopeManager.Begin("p",
+                                                      string.Empty,
+                                                      DefaultExecuteChildContentAsync,
+                                                      DefaultStartWritingScope,
+                                                      DefaultEndWritingScope);
+            executionContext = scopeManager.Begin("div",
+                                                  string.Empty,
+                                                  DefaultExecuteChildContentAsync,
+                                                  DefaultStartWritingScope,
+                                                  DefaultEndWritingScope);
 
             // Assert
             Assert.Equal("div", executionContext.TagName);
@@ -43,8 +62,16 @@ namespace Microsoft.AspNet.Razor.Runtime.Test.TagHelpers
             var scopeManager = new TagHelperScopeManager();
 
             // Act
-            var executionContext = scopeManager.Begin("p");
-            executionContext = scopeManager.Begin("div");
+            var executionContext = scopeManager.Begin("p",
+                                                      string.Empty,
+                                                      DefaultExecuteChildContentAsync,
+                                                      DefaultStartWritingScope,
+                                                      DefaultEndWritingScope);
+            executionContext = scopeManager.Begin("div",
+                                                  string.Empty,
+                                                  DefaultExecuteChildContentAsync,
+                                                  DefaultStartWritingScope,
+                                                  DefaultEndWritingScope);
             executionContext = scopeManager.End();
 
             // Assert
@@ -58,8 +85,16 @@ namespace Microsoft.AspNet.Razor.Runtime.Test.TagHelpers
             var scopeManager = new TagHelperScopeManager();
 
             // Act
-            var executionContext = scopeManager.Begin("p");
-            executionContext = scopeManager.Begin("div");
+            var executionContext = scopeManager.Begin("p",
+                                                      string.Empty,
+                                                      DefaultExecuteChildContentAsync,
+                                                      DefaultStartWritingScope,
+                                                      DefaultEndWritingScope);
+            executionContext = scopeManager.Begin("div",
+                                                  string.Empty,
+                                                  DefaultExecuteChildContentAsync,
+                                                  DefaultStartWritingScope,
+                                                  DefaultEndWritingScope);
             executionContext = scopeManager.End();
             executionContext = scopeManager.End();
 
@@ -85,7 +120,6 @@ namespace Microsoft.AspNet.Razor.Runtime.Test.TagHelpers
             });
 
             Assert.Equal(expectedError, ex.Message);
-
         }
     }
 }

test/Microsoft.AspNet.Razor.Runtime.Test/TagHelpers/TagHelperTypeResolverTest.cs

@@ -114,14 +114,14 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             public TestTagHelperTypeResolver(IEnumerable<Type> assemblyTypes)
             {
                 _assemblyTypeInfos = assemblyTypes.Select(type => type.GetTypeInfo());
-                OnGetLibraryDefinedTypes = (_) => { };
+                OnGetExportedTypes = (_) => { };
             }
 
-            public Action<AssemblyName> OnGetLibraryDefinedTypes { get; set; }
+            public Action<AssemblyName> OnGetExportedTypes { get; set; }
 
-            internal override IEnumerable<TypeInfo> GetLibraryDefinedTypes(AssemblyName assemblyName)
+            protected override IEnumerable<TypeInfo> GetExportedTypes(AssemblyName assemblyName)
             {
-                OnGetLibraryDefinedTypes(assemblyName);
+                OnGetExportedTypes(assemblyName);
 
                 return _assemblyTypeInfos;
             }

test/Microsoft.AspNet.Razor.Runtime.Test/project.json

@@ -3,15 +3,16 @@
     "dependencies": {
         "Microsoft.AspNet.Razor.Runtime": "4.0.0-*",
         "Microsoft.AspNet.Testing": "1.0.0-*",
-        "Xunit.KRunner": "1.0.0-*"
+        "xunit.runner.kre": "1.0.0-*"
     },
     "commands": {
-        "test": "Xunit.KRunner"
+        "test": "xunit.runner.kre"
     },
     "frameworks": {
         "aspnet50": { },
         "aspnetcore50": {
             "dependencies": {
+                "System.Reflection.TypeExtensions": "4.0.0-beta-*",
                 "System.Runtime.Extensions": "4.0.10-beta-*"
             }
         }

test/Microsoft.AspNet.Razor.Test/CSharpRazorCodeLanguageTest.cs

@@ -54,7 +54,8 @@ namespace Microsoft.AspNet.Razor.Test
                 "myclass",
                 "myns",
                 string.Empty,
-                shouldGenerateLinePragmas: false);
+                shouldGenerateLinePragmas: false,
+                errorSink: new ParserErrorSink());
 
             // Act
             var generator = language.CreateCodeBuilder(codeBuilderContext);

test/Microsoft.AspNet.Razor.Test/Framework/ParserTestBase.cs

@@ -434,28 +434,30 @@ namespace Microsoft.AspNet.Razor.Test.Framework
             collector.AddError("{0} - FAILED :: Actual: << Null >>", expected);
         }
 
-        public static void EvaluateRazorErrors(IList<RazorError> actualErrors, IList<RazorError> expectedErrors)
+        public static void EvaluateRazorErrors(IEnumerable<RazorError> actualErrors, IList<RazorError> expectedErrors)
         {
+            var realCount = actualErrors.Count();
+
             // Evaluate the errors
             if (expectedErrors == null || expectedErrors.Count == 0)
             {
-                Assert.True(actualErrors.Count == 0,
+                Assert.True(realCount == 0,
                             String.Format("Expected that no errors would be raised, but the following errors were:\r\n{0}", FormatErrors(actualErrors)));
             }
             else
             {
-                Assert.True(expectedErrors.Count == actualErrors.Count,
+                Assert.True(expectedErrors.Count == realCount,
                             String.Format("Expected that {0} errors would be raised, but {1} errors were.\r\nExpected Errors: \r\n{2}\r\nActual Errors: \r\n{3}",
                                           expectedErrors.Count,
-                                          actualErrors.Count,
+                                          realCount,
                                           FormatErrors(expectedErrors),
                                           FormatErrors(actualErrors)));
-                Assert.Equal(expectedErrors.ToArray(), actualErrors.ToArray());
+                Assert.Equal(expectedErrors, actualErrors);
             }
             WriteTraceLine("Expected Errors were raised:\r\n{0}", FormatErrors(expectedErrors));
         }
 
-        public static string FormatErrors(IList<RazorError> errors)
+        public static string FormatErrors(IEnumerable<RazorError> errors)
         {
             if (errors == null)
             {

test/Microsoft.AspNet.Razor.Test/Framework/TestSpanBuilder.cs

@@ -300,11 +300,6 @@ namespace Microsoft.AspNet.Razor.Test.Framework
             return _self.With(new SetBaseTypeCodeGenerator(baseType));
         }
 
-        public SpanConstructor AsRazorDirectiveAttribute(string key, string value)
-        {
-            return _self.With(new RazorDirectiveAttributeCodeGenerator(key, value));
-        }
-
         public SpanConstructor AsAddTagHelper(string lookupText)
         {
             return _self.With(

test/Microsoft.AspNet.Razor.Test/Generator/CSharpTagHelperRenderingTest.cs

@@ -26,21 +26,18 @@ namespace Microsoft.AspNet.Razor.Test.Generator
                     new TagHelperDescriptor("p",
                                             "PTagHelper",
                                             "SomeAssembly",
-                                            ContentBehavior.None,
                                             new [] {
                                                 new TagHelperAttributeDescriptor("age", pAgePropertyInfo)
                                             }),
                     new TagHelperDescriptor("input",
                                             "InputTagHelper",
                                             "SomeAssembly",
-                                            ContentBehavior.None,
                                             new TagHelperAttributeDescriptor[] {
                                                 new TagHelperAttributeDescriptor("type", inputTypePropertyInfo)
                                             }),
                     new TagHelperDescriptor("input",
                                             "InputTagHelper2",
                                             "SomeAssembly",
-                                            ContentBehavior.None,
                                             new TagHelperAttributeDescriptor[] {
                                                 new TagHelperAttributeDescriptor("type", inputTypePropertyInfo),
                                                 new TagHelperAttributeDescriptor("checked", checkedPropertyInfo)
@@ -49,21 +46,6 @@ namespace Microsoft.AspNet.Razor.Test.Generator
             }
         }
 
-        private static IEnumerable<TagHelperDescriptor> ContentBehaviorTagHelperDescriptors
-        {
-            get
-            {
-                return new[]
-                {
-                    new TagHelperDescriptor("modify", "ModifyTagHelper", "SomeAssembly", ContentBehavior.Modify),
-                    new TagHelperDescriptor("none", "NoneTagHelper", "SomeAssembly", ContentBehavior.None),
-                    new TagHelperDescriptor("append", "AppendTagHelper", "SomeAssembly", ContentBehavior.Append),
-                    new TagHelperDescriptor("prepend", "PrependTagHelper", "SomeAssembly", ContentBehavior.Prepend),
-                    new TagHelperDescriptor("replace", "ReplaceTagHelper", "SomeAssembly", ContentBehavior.Replace)
-                };
-            }
-        }
-
         public static TheoryData TagHelperDescriptorFlowTestData
         {
             get
@@ -109,13 +91,6 @@ namespace Microsoft.AspNet.Razor.Test.Generator
                         Enumerable.Empty<TagHelperDescriptor>(),
                         false
                     },
-                    {
-                        "ContentBehaviorTagHelpers",
-                        "ContentBehaviorTagHelpers",
-                        ContentBehaviorTagHelperDescriptors,
-                        ContentBehaviorTagHelperDescriptors,
-                        false
-                    },
                     {
                         "ComplexTagHelpers",
                         "ComplexTagHelpers",
@@ -144,7 +119,7 @@ namespace Microsoft.AspNet.Razor.Test.Generator
             bool designTimeMode)
         {
             RunTagHelperTest(
-                testName, 
+                testName,
                 baseLineName: baselineName,
                 tagHelperDescriptors: tagHelperDescriptors,
                 onResults: (results) =>
@@ -174,7 +149,13 @@ namespace Microsoft.AspNet.Razor.Test.Generator
                                              generatedAbsoluteIndex: 475,
                                              generatedLineIndex: 15,
                                              characterOffsetIndex: 14,
-                                             contentLength: 11)
+                                             contentLength: 11),
+                            BuildLineMapping(documentAbsoluteIndex: 57,
+                                             documentLineIndex: 2,
+                                             generatedAbsoluteIndex: 958,
+                                             generatedLineIndex: 34,
+                                             characterOffsetIndex: 28,
+                                             contentLength: 4)
                         }
                     },
                     {
@@ -188,21 +169,13 @@ namespace Microsoft.AspNet.Razor.Test.Generator
                                              generatedAbsoluteIndex: 475,
                                              generatedLineIndex: 15,
                                              characterOffsetIndex: 14,
-                                             contentLength: 11)
-                        }
-                    },
-                    {
-                        "ContentBehaviorTagHelpers",
-                        "ContentBehaviorTagHelpers.DesignTime",
-                        ContentBehaviorTagHelperDescriptors,
-                        new List<LineMapping>
-                        {
-                            BuildLineMapping(documentAbsoluteIndex: 14,
-                                             documentLineIndex: 0,
-                                             generatedAbsoluteIndex: 495,
-                                             generatedLineIndex: 15,
-                                             characterOffsetIndex: 14,
-                                             contentLength: 11)
+                                             contentLength: 11),
+                            BuildLineMapping(documentAbsoluteIndex: 189,
+                                             documentLineIndex: 6,
+                                             generatedAbsoluteIndex: 1574,
+                                             generatedLineIndex: 44,
+                                             characterOffsetIndex: 40,
+                                             contentLength: 4)
                         }
                     },
                     {
@@ -213,17 +186,32 @@ namespace Microsoft.AspNet.Razor.Test.Generator
                         {
                             BuildLineMapping(14, 0, 479, 15, 14, 11),
                             BuildLineMapping(30, 2, 1, 995, 35, 0, 48),
-                            BuildLineMapping(157, 7, 32, 1177, 45, 6, 12),
-                            BuildLineMapping(205, 9, 1260, 50, 0, 12),
-                            BuildLineMapping(218, 9, 13, 1356, 56, 12, 27),
-                            BuildLineMapping(346, 12, 1754, 68, 0, 48),
-                            BuildLineMapping(440, 15, 46, 2004, 78, 6, 8),
-                            BuildLineMapping(501, 16, 31, 2384, 88, 6, 30),
-                            BuildLineMapping(568, 17, 30, 2733, 97, 0, 10),
-                            BuildLineMapping(601, 17, 63, 2815, 103, 0, 8),
-                            BuildLineMapping(632, 17, 94, 2895, 109, 0, 1),
-                            BuildLineMapping(639, 18, 3149, 118, 0, 15),
-                            BuildLineMapping(680, 21, 3234, 124, 0, 1)
+                            BuildLineMapping(205, 9, 1113, 44, 0, 12),
+                            BuildLineMapping(218, 9, 13, 1209, 50, 12, 27),
+                            BuildLineMapping(346, 12, 1607, 62, 0, 48),
+                            BuildLineMapping(440, 15, 46, 1798, 71, 6, 8),
+                            BuildLineMapping(457, 15, 2121, 79, 63, 4),
+                            BuildLineMapping(501, 16, 31, 2328, 86, 6, 30),
+                            BuildLineMapping(568, 17, 30, 2677, 95, 0, 10),
+                            BuildLineMapping(601, 17, 63, 2759, 101, 0, 8),
+                            BuildLineMapping(632, 17, 94, 2839, 107, 0, 1),
+                            BuildLineMapping(639, 18, 3093, 116, 0, 15),
+                            BuildLineMapping(157, 7, 32, 3242, 123, 6, 12),
+                            BuildLineMapping(719, 21, 3325, 128, 0, 12),
+                            BuildLineMapping(733, 21, 3423, 134, 14, 21),
+                            BuildLineMapping(787, 22, 30, 3680, 142, 28, 7),
+                            BuildLineMapping(685, 20, 17, 3836, 148, 19, 23),
+                            BuildLineMapping(708, 20, 40, 3859, 148, 42, 7),
+                            BuildLineMapping(897, 25, 30, 4101, 155, 28, 30),
+                            BuildLineMapping(831, 24, 16, 4280, 161, 19, 8),
+                            BuildLineMapping(840, 24, 25, 4288, 161, 27, 23),
+                            BuildLineMapping(1026, 28, 4546, 168, 28, 30),
+                            BuildLineMapping(964, 27, 16, 4725, 174, 19, 30),
+                            BuildLineMapping(1156, 31, 4990, 181, 28, 3),
+                            BuildLineMapping(1161, 31, 33, 4993, 181, 31, 27),
+                            BuildLineMapping(1189, 31, 61, 5020, 181, 58, 10),
+                            BuildLineMapping(1094, 30, 18, 5179, 187, 19, 29),
+                            BuildLineMapping(1231, 34, 5279, 192, 0, 1),
                         }
                     }
                 };
@@ -256,7 +244,6 @@ namespace Microsoft.AspNet.Razor.Test.Generator
                     { "SingleTagHelper", PAndInputTagHelperDescriptors },
                     { "BasicTagHelpers", PAndInputTagHelperDescriptors },
                     { "BasicTagHelpers.RemoveTagHelper", PAndInputTagHelperDescriptors },
-                    { "ContentBehaviorTagHelpers", ContentBehaviorTagHelperDescriptors },
                     { "ComplexTagHelpers", PAndInputTagHelperDescriptors },
                 };
             }
@@ -312,7 +299,7 @@ namespace Microsoft.AspNet.Razor.Test.Generator
             RunTagHelperTest("AddTagHelperDirective",
                              designTimeMode: true,
                              tagHelperDescriptors: new[] {
-                                new TagHelperDescriptor("p", "pTagHelper", "SomeAssembly", ContentBehavior.None)
+                                new TagHelperDescriptor("p", "pTagHelper", "SomeAssembly")
                              });
         }
 
@@ -328,12 +315,11 @@ namespace Microsoft.AspNet.Razor.Test.Generator
                 new TagHelperDescriptor("MyTagHelper",
                                         "MyTagHelper",
                                         "SomeAssembly",
-                                        ContentBehavior.None,
                                         new [] {
                                             new TagHelperAttributeDescriptor("BoundProperty",
                                                                              propertyInfo)
                                         }),
-                new TagHelperDescriptor("NestedTagHelper", "NestedTagHelper", "SomeAssembly", ContentBehavior.Modify)
+                new TagHelperDescriptor("NestedTagHelper", "NestedTagHelper", "SomeAssembly")
             };
 
             // Act & Assert

test/Microsoft.AspNet.Razor.Test/Generator/CSharpTagHelperRenderingUnitTest.cs

@@ -0,0 +1,188 @@
+using System.Collections.Generic;
+using Microsoft.AspNet.Razor.Generator;
+using Microsoft.AspNet.Razor.Generator.Compiler;
+using Microsoft.AspNet.Razor.Generator.Compiler.CSharp;
+using Microsoft.AspNet.Razor.Parser;
+using Microsoft.AspNet.Razor.TagHelpers;
+using Xunit;
+
+namespace Microsoft.AspNet.Razor.Test.Generator
+{
+    public class CSharpTagHelperRenderingUnitTest
+    {
+        [Fact]
+        public void CreatesAUniqueIdForSingleTagHelperChunk()
+        {
+            // Arrange
+            var chunk = CreateTagHelperChunk("div", new[] {
+                new TagHelperDescriptor("div", "DivTagHelper", "FakeAssemblyName")
+            });
+            var codeRenderer = CreateCodeRenderer();
+
+            // Act
+            codeRenderer.RenderTagHelper(chunk);
+
+            // Assert
+            Assert.Equal(1, codeRenderer.GenerateUniqueIdCount);
+        }
+
+        [Fact]
+        public void UsesTheSameUniqueIdForTagHelperChunkWithMultipleTagHelpers()
+        {
+            // Arrange
+            var chunk = CreateTagHelperChunk("div", new[] {
+                new TagHelperDescriptor("div", "DivTagHelper", "FakeAssemblyName"),
+                new TagHelperDescriptor("div", "Div2TagHelper", "FakeAssemblyName")
+            });
+            var codeRenderer = CreateCodeRenderer();
+
+            // Act
+            codeRenderer.RenderTagHelper(chunk);
+
+            // Assert
+            Assert.Equal(1, codeRenderer.GenerateUniqueIdCount);
+        }
+
+        [Fact]
+        public void UsesDifferentUniqueIdForMultipleTagHelperChunksForSameTagHelper()
+        {
+            // Arrange
+            var chunk1 = CreateTagHelperChunk("div", new[] {
+                new TagHelperDescriptor("div", "DivTagHelper", "FakeAssemblyName")
+            });
+            var chunk2 = CreateTagHelperChunk("div", new[] {
+                new TagHelperDescriptor("div", "DivTagHelper", "FakeAssemblyName")
+            });
+            var codeRenderer = CreateCodeRenderer();
+
+            // Act
+            codeRenderer.RenderTagHelper(chunk1);
+            codeRenderer.RenderTagHelper(chunk2);
+
+            // Assert
+            Assert.Equal(2, codeRenderer.GenerateUniqueIdCount);
+        }
+
+        [Fact]
+        public void UsesDifferentUniqueIdForNestedTagHelperChunksForSameTagHelper()
+        {
+            // Arrange
+            var parentChunk = CreateTagHelperChunk("div", new[] {
+                new TagHelperDescriptor("div", "DivTagHelper", "FakeAssemblyName")
+            });
+            var childChunk = CreateTagHelperChunk("div", new[] {
+                new TagHelperDescriptor("div", "DivTagHelper", "FakeAssemblyName")
+            });
+            parentChunk.Children.Add(childChunk);
+            var codeRenderer = CreateCodeRenderer();
+
+            // Act
+            codeRenderer.RenderTagHelper(parentChunk);
+
+            // Assert
+            Assert.Equal(2, codeRenderer.GenerateUniqueIdCount);
+        }
+
+        [Fact]
+        public void UsesDifferentUniqueIdForMultipleTagHelperChunksForDifferentTagHelpers()
+        {
+            // Arrange
+            var divChunk = CreateTagHelperChunk("div", new[] {
+                new TagHelperDescriptor("div", "DivTagHelper", "FakeAssemblyName")
+            });
+            var spanChunk = CreateTagHelperChunk("span", new[] {
+                new TagHelperDescriptor("span", "SpanTagHelper", "FakeAssemblyName")
+            });
+            var codeRenderer = CreateCodeRenderer();
+
+            // Act
+            codeRenderer.RenderTagHelper(divChunk);
+            codeRenderer.RenderTagHelper(spanChunk);
+
+            // Assert
+            Assert.Equal(2, codeRenderer.GenerateUniqueIdCount);
+        }
+
+        [Fact]
+        public void UsesCorrectUniqueIdForMultipleTagHelperChunksSomeWithSameSameTagHelpersSomeWithDifferentTagHelpers()
+        {
+            // Arrange
+            var chunk1 = CreateTagHelperChunk("div", new[] {
+                new TagHelperDescriptor("div", "DivTagHelper", "FakeAssemblyName"),
+                new TagHelperDescriptor("div", "Div2TagHelper", "FakeAssemblyName")
+            });
+            var chunk2 = CreateTagHelperChunk("span", new[] {
+                new TagHelperDescriptor("span", "SpanTagHelper", "FakeAssemblyName")
+            });
+            var chunk3 = CreateTagHelperChunk("span", new[] {
+                new TagHelperDescriptor("span", "SpanTagHelper", "FakeAssemblyName"),
+                new TagHelperDescriptor("span", "Span2TagHelper", "FakeAssemblyName")
+            });
+            var codeRenderer = CreateCodeRenderer();
+
+            // Act
+            codeRenderer.RenderTagHelper(chunk1);
+            codeRenderer.RenderTagHelper(chunk2);
+            codeRenderer.RenderTagHelper(chunk3);
+
+            // Assert
+            Assert.Equal(3, codeRenderer.GenerateUniqueIdCount);
+        }
+
+        private static TagHelperChunk CreateTagHelperChunk(string tagName, IEnumerable<TagHelperDescriptor> tagHelperDescriptors)
+        {
+            return new TagHelperChunk
+            {
+                TagName = tagName,
+                Descriptors = tagHelperDescriptors,
+                Children = new List<Chunk>(),
+                Attributes = new Dictionary<string, Chunk>()
+            };
+        }
+
+        private static TrackingUniqueIdsTagHelperCodeRenderer CreateCodeRenderer()
+        {
+            var writer = new CSharpCodeWriter();
+            var codeBuilderContext = CreateContext();
+            var visitor = new CSharpCodeVisitor(writer, codeBuilderContext);
+            var codeRenderer = new TrackingUniqueIdsTagHelperCodeRenderer(
+                visitor,
+                writer,
+                codeBuilderContext);
+            visitor.TagHelperRenderer = codeRenderer;
+            return codeRenderer;
+        }
+
+        private static CodeBuilderContext CreateContext()
+        {
+            return new CodeBuilderContext(
+                new CodeGeneratorContext(
+                    new RazorEngineHost(new CSharpRazorCodeLanguage()),
+                    "MyClass",
+                    "MyNamespace",
+                    string.Empty,
+                    shouldGenerateLinePragmas: true),
+                new ParserErrorSink());
+        }
+
+        private class TrackingUniqueIdsTagHelperCodeRenderer : CSharpTagHelperCodeRenderer
+        {
+            public TrackingUniqueIdsTagHelperCodeRenderer(
+                IChunkVisitor bodyVisitor,
+                CSharpCodeWriter writer,
+                CodeBuilderContext context)
+                : base(bodyVisitor, writer, context)
+            {
+
+            }
+
+            protected override string GenerateUniqueId()
+            {
+                GenerateUniqueIdCount++;
+                return "test";
+            }
+
+            public int GenerateUniqueIdCount { get; private set; }
+        }
+    }
+}

test/Microsoft.AspNet.Razor.Test/Generator/CodeTree/CSharpCodeBuilderTests.cs

@@ -3,6 +3,7 @@
 
 #if !ASPNETCORE50
 using Microsoft.AspNet.Razor.Generator;
+using Microsoft.AspNet.Razor.Parser;
 using Microsoft.AspNet.Razor.Parser.SyntaxTree;
 using Microsoft.AspNet.Razor.Test.Utils;
 using Moq;
@@ -23,7 +24,8 @@ namespace Microsoft.AspNet.Razor.Test.Generator.CodeTree
                 "TestClass",
                 "TestNamespace",
                 "Foo.cs",
-                shouldGenerateLinePragmas: false);
+                shouldGenerateLinePragmas: false,
+                errorSink: new ParserErrorSink());
             codeBuilderContext.CodeTreeBuilder.AddUsingChunk("FakeNamespace1", syntaxTreeNode.Object);
             codeBuilderContext.CodeTreeBuilder.AddUsingChunk("FakeNamespace2.SubNamespace", syntaxTreeNode.Object);
             var codeBuilder = language.CreateCodeBuilder(codeBuilderContext);

test/Microsoft.AspNet.Razor.Test/Generator/CodeTree/ChunkVisitorTests.cs

@@ -4,6 +4,7 @@
 #if !ASPNETCORE50
 using Microsoft.AspNet.Razor.Generator;
 using Microsoft.AspNet.Razor.Generator.Compiler;
+using Microsoft.AspNet.Razor.Parser;
 using Moq;
 using Moq.Protected;
 using Xunit;
@@ -34,7 +35,8 @@ namespace Microsoft.AspNet.Razor
                 "myclass",
                 "myns",
                 string.Empty,
-                shouldGenerateLinePragmas: false);
+                shouldGenerateLinePragmas: false,
+                errorSink: new ParserErrorSink());
             var writer = Mock.Of<CodeWriter>();
             return new Mock<ChunkVisitor<CodeWriter>>(writer, codeBuilderContext);
         }

test/Microsoft.AspNet.Razor.Test/Generator/RazorCodeGeneratorTest.cs

@@ -181,17 +181,13 @@ namespace Microsoft.AspNet.Razor.Test.Generator
 
                 if (expectedDesignTimePragmas != null)
                 {
-                    Assert.True(results.DesignTimeLineMappings != null && results.DesignTimeLineMappings.Count > 0);
+                    Assert.True(results.DesignTimeLineMappings != null); // Guard
+                    for (var i = 0; i < expectedDesignTimePragmas.Count && i < results.DesignTimeLineMappings.Count; i++)
+                    {
+                        Assert.Equal(expectedDesignTimePragmas[i], results.DesignTimeLineMappings[i]);
+                    }
 
                     Assert.Equal(expectedDesignTimePragmas.Count, results.DesignTimeLineMappings.Count);
-
-                    for (var i = 0; i < expectedDesignTimePragmas.Count; i++)
-                    {
-                        if (!expectedDesignTimePragmas[i].Equals(results.DesignTimeLineMappings[i]))
-                        {
-                            Assert.True(false, String.Format("Line mapping {0} is not equivalent.", i));
-                        }
-                    }
                 }
             }
         }

test/Microsoft.AspNet.Razor.Test/Generator/TagHelperAttributeValueCodeRendererTest.cs

@@ -23,18 +23,16 @@ namespace Microsoft.AspNet.Razor.Test.Generator
             var checkedPropertyInfo = typeof(TestType).GetProperty("Checked");
             var tagHelperDescriptors = new TagHelperDescriptor[]
             {
-                new TagHelperDescriptor("p", "PTagHelper", "SomeAssembly", ContentBehavior.None),
+                new TagHelperDescriptor("p", "PTagHelper", "SomeAssembly"),
                 new TagHelperDescriptor("input",
                                         "InputTagHelper",
                                         "SomeAssembly",
-                                        ContentBehavior.None,
                                         new TagHelperAttributeDescriptor[] {
                                             new TagHelperAttributeDescriptor("type", inputTypePropertyInfo)
                                         }),
                 new TagHelperDescriptor("input",
                                         "InputTagHelper2",
                                         "SomeAssembly",
-                                        ContentBehavior.None,
                                         new TagHelperAttributeDescriptor[] {
                                             new TagHelperAttributeDescriptor("type", inputTypePropertyInfo),
                                             new TagHelperAttributeDescriptor("checked", checkedPropertyInfo)
@@ -65,7 +63,7 @@ namespace Microsoft.AspNet.Razor.Test.Generator
             }
         }
 
-        private class AttributeCodeGeneratorReplacingCodeBuilder : CSharpCodeBuilder
+        private class AttributeCodeGeneratorReplacingCodeBuilder : TestCSharpCodeBuilder
         {
             public AttributeCodeGeneratorReplacingCodeBuilder(CodeBuilderContext context)
                 : base(context)
@@ -88,11 +86,12 @@ namespace Microsoft.AspNet.Razor.Test.Generator
             public override void RenderAttributeValue([NotNull] TagHelperAttributeDescriptor attributeInfo,
                                                       [NotNull] CSharpCodeWriter writer,
                                                       [NotNull] CodeBuilderContext context,
-                                                      [NotNull] Action<CSharpCodeWriter> renderAttributeValue)
+                                                      [NotNull] Action<CSharpCodeWriter> renderAttributeValue,
+                                                      bool complexValue)
             {
                 writer.Write("**From custom attribute code renderer**: ");
 
-                base.RenderAttributeValue(attributeInfo, writer, context, renderAttributeValue);
+                base.RenderAttributeValue(attributeInfo, writer, context, renderAttributeValue, complexValue);
             }
         }
 

test/Microsoft.AspNet.Razor.Test/Generator/TagHelperTestBase.cs

@@ -5,7 +5,9 @@ using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
+using Microsoft.AspNet.Razor.Generator;
 using Microsoft.AspNet.Razor.Generator.Compiler;
+using Microsoft.AspNet.Razor.Generator.Compiler.CSharp;
 using Microsoft.AspNet.Razor.Parser;
 using Microsoft.AspNet.Razor.TagHelpers;
 using Xunit;
@@ -78,6 +80,11 @@ namespace Microsoft.AspNet.Razor.Test.Generator
                 _tagHelperDescriptors = tagHelperDescriptors;
             }
 
+            protected internal override CodeBuilder CreateCodeBuilder(CodeBuilderContext context)
+            {
+                return Host.DecorateCodeBuilder(new TestCSharpCodeBuilder(context), context);
+            }
+
             protected internal override RazorParser CreateParser(string fileName)
             {
                 var parser = base.CreateParser(fileName);
@@ -87,5 +94,37 @@ namespace Microsoft.AspNet.Razor.Test.Generator
                                        new CustomTagHelperDescriptorResolver(_tagHelperDescriptors));
             }
         }
+
+        protected class TestCSharpCodeBuilder : CSharpCodeBuilder
+        {
+            public TestCSharpCodeBuilder(CodeBuilderContext context)
+                : base(context)
+            {
+
+            }
+
+            protected override CSharpCodeVisitor CreateCSharpCodeVisitor(CSharpCodeWriter writer, CodeBuilderContext context)
+            {
+                var visitor = base.CreateCSharpCodeVisitor(writer, context);
+                visitor.TagHelperRenderer = new NoUniqueIdsTagHelperCodeRenderer(visitor, writer, context);
+                return visitor;
+            }
+
+            private class NoUniqueIdsTagHelperCodeRenderer : CSharpTagHelperCodeRenderer
+            {
+                public NoUniqueIdsTagHelperCodeRenderer(IChunkVisitor bodyVisitor,
+                                                        CSharpCodeWriter writer,
+                                                        CodeBuilderContext context)
+                    : base(bodyVisitor, writer, context)
+                {
+
+                }
+
+                protected override string GenerateUniqueId()
+                {
+                    return "test";
+                }
+            }
+        }
     }
 }

test/Microsoft.AspNet.Razor.Test/Parser/CSharp/CSharpDirectivesTest.cs

@@ -247,32 +247,6 @@ namespace Microsoft.AspNet.Razor.Test.Parser.CSharp
                            .AsBaseType("$rootnamespace$.MyBase")));
         }
 
-        [Fact]
-        public void SessionStateDirectiveWorks()
-        {
-            ParseBlockTest("@sessionstate InProc",
-                           new DirectiveBlock(
-                               Factory.CodeTransition(),
-                               Factory.MetaCode(SyntaxConstants.CSharp.SessionStateKeyword + " ")
-                                   .Accepts(AcceptedCharacters.None),
-                               Factory.Code("InProc")
-                                      .AsRazorDirectiveAttribute("sessionstate", "InProc")
-                               ));
-        }
-
-        [Fact]
-        public void SessionStateDirectiveParsesInvalidSessionValue()
-        {
-            ParseBlockTest("@sessionstate Blah",
-                           new DirectiveBlock(
-                               Factory.CodeTransition(),
-                               Factory.MetaCode(SyntaxConstants.CSharp.SessionStateKeyword + " ")
-                                   .Accepts(AcceptedCharacters.None),
-                               Factory.Code("Blah")
-                                   .AsRazorDirectiveAttribute("sessionstate", "Blah")
-                               ));
-        }
-
         [Fact]
         public void FunctionsDirective()
         {

test/Microsoft.AspNet.Razor.Test/Parser/Html/HtmlAttributeTest.cs

@@ -190,7 +190,7 @@ namespace Microsoft.AspNet.Razor.Test.Parser.Html
             var rewritten = rewritingContext.SyntaxTree;
 
             // Assert
-            Assert.Equal(0, results.ParserErrors.Count);
+            Assert.Equal(0, results.ParserErrors.Count());
             EvaluateParseTree(rewritten,
                 new MarkupBlock(
                     new MarkupTagBlock(
@@ -277,7 +277,7 @@ namespace Microsoft.AspNet.Razor.Test.Parser.Html
             var rewritten = rewritingContext.SyntaxTree;
 
             // Assert
-            Assert.Equal(0, results.ParserErrors.Count);
+            Assert.Equal(0, results.ParserErrors.Count());
             Assert.Equal(rewritten.Children.Count(), results.Document.Children.Count());
         }
 

test/Microsoft.AspNet.Razor.Test/Parser/ParserVisitorExtensionsTest.cs

@@ -19,9 +19,10 @@ namespace Microsoft.AspNet.Razor.Test.Parser
         public void VisitThrowsOnNullVisitor()
         {
             ParserVisitor target = null;
+            var errorSink = new ParserErrorSink();
             var results = new ParserResults(new BlockBuilder() { Type = BlockType.Comment }.Build(),
                                             Enumerable.Empty<TagHelperDescriptor>(),
-                                            parserErrors: new List<RazorError>());
+                                            errorSink);
 
             Assert.Throws<ArgumentNullException>("self", () => target.Visit(results));
         }
@@ -39,9 +40,10 @@ namespace Microsoft.AspNet.Razor.Test.Parser
             // Arrange
             Mock<ParserVisitor> targetMock = new Mock<ParserVisitor>();
             var root = new BlockBuilder() { Type = BlockType.Comment }.Build();
+            var errorSink = new ParserErrorSink();
             var results = new ParserResults(root,
                                             Enumerable.Empty<TagHelperDescriptor>(),
-                                            parserErrors: new List<RazorError>());
+                                            errorSink);
 
             // Act
             targetMock.Object.Visit(results);
@@ -56,11 +58,17 @@ namespace Microsoft.AspNet.Razor.Test.Parser
             // Arrange
             Mock<ParserVisitor> targetMock = new Mock<ParserVisitor>();
             var root = new BlockBuilder() { Type = BlockType.Comment }.Build();
-            List<RazorError> errors = new List<RazorError>() {
+            var errorSink = new ParserErrorSink();
+            List<RazorError> errors = new List<RazorError>
+            {
                 new RazorError("Foo", 1, 0, 1),
-                new RazorError("Bar", 2, 0, 2)
+                new RazorError("Bar", 2, 0, 2),
             };
-            var results = new ParserResults(root, Enumerable.Empty<TagHelperDescriptor>(), errors);
+            foreach (var error in errors)
+            {
+                errorSink.OnError(error);
+            }
+            var results = new ParserResults(root, Enumerable.Empty<TagHelperDescriptor>(), errorSink);
 
             // Act
             targetMock.Object.Visit(results);
@@ -76,11 +84,10 @@ namespace Microsoft.AspNet.Razor.Test.Parser
             // Arrange
             Mock<ParserVisitor> targetMock = new Mock<ParserVisitor>();
             var root = new BlockBuilder() { Type = BlockType.Comment }.Build();
-            List<RazorError> errors = new List<RazorError>() {
-                new RazorError("Foo", 1, 0, 1),
-                new RazorError("Bar", 2, 0, 2)
-            };
-            var results = new ParserResults(root, Enumerable.Empty<TagHelperDescriptor>(), errors);
+            var errorSink = new ParserErrorSink();
+            errorSink.OnError(new RazorError("Foo", 1, 0, 1));
+            errorSink.OnError(new RazorError("Bar", 2, 0, 2));
+            var results = new ParserResults(root, Enumerable.Empty<TagHelperDescriptor>(), errorSink);
 
             // Act
             targetMock.Object.Visit(results);

test/Microsoft.AspNet.Razor.Test/RazorTemplateEngineTest.cs

@@ -119,7 +119,8 @@ namespace Microsoft.AspNet.Razor.Test
                 "different-class",
                 "different-ns",
                 string.Empty,
-                shouldGenerateLinePragmas: true);
+                shouldGenerateLinePragmas: true,
+                errorSink: new ParserErrorSink());
 
             var expected = new CSharpCodeBuilder(codeBuilderContext);
 

test/Microsoft.AspNet.Razor.Test/TagHelpers/AddOrRemoveTagHelperSpanVisitorTest.cs

@@ -168,8 +168,10 @@ namespace Microsoft.AspNet.Razor.TagHelpers
                     new ParserErrorSink());
             var document = new MarkupBlock(Factory.Markup("Hello World"));
 
-            // Act & Assert
-            Assert.DoesNotThrow(() => addOrRemoveTagHelperSpanVisitor.GetDescriptors(document));
+            // Act
+            var descriptors = addOrRemoveTagHelperSpanVisitor.GetDescriptors(document);
+
+            Assert.Empty(descriptors);
         }
 
         private class TestTagHelperDescriptorResolver : ITagHelperDescriptorResolver

test/Microsoft.AspNet.Razor.Test/TagHelpers/TagHelperDescriptorProviderTest.cs

@@ -13,8 +13,8 @@ namespace Microsoft.AspNet.Razor.Test.TagHelpers
         public void TagHelperDescriptorProvider_GetTagHelpersReturnsNothingForUnregisteredTags()
         {
             // Arrange
-            var divDescriptor = new TagHelperDescriptor("div", "foo1", "SomeAssembly", ContentBehavior.None);
-            var spanDescriptor = new TagHelperDescriptor("span", "foo2", "SomeAssembly", ContentBehavior.None);
+            var divDescriptor = new TagHelperDescriptor("div", "foo1", "SomeAssembly");
+            var spanDescriptor = new TagHelperDescriptor("span", "foo2", "SomeAssembly");
             var descriptors = new TagHelperDescriptor[] { divDescriptor, spanDescriptor };
             var provider = new TagHelperDescriptorProvider(descriptors);
 
@@ -29,9 +29,9 @@ namespace Microsoft.AspNet.Razor.Test.TagHelpers
         public void TagHelperDescriptorProvider_GetTagHelpersDoesNotReturnNonCatchAllTagsForCatchAll()
         {
             // Arrange
-            var divDescriptor = new TagHelperDescriptor("div", "foo1", "SomeAssembly", ContentBehavior.None);
-            var spanDescriptor = new TagHelperDescriptor("span", "foo2", "SomeAssembly", ContentBehavior.None);
-            var catchAllDescriptor = new TagHelperDescriptor("*", "foo3", "SomeAssembly", ContentBehavior.None);
+            var divDescriptor = new TagHelperDescriptor("div", "foo1", "SomeAssembly");
+            var spanDescriptor = new TagHelperDescriptor("span", "foo2", "SomeAssembly");
+            var catchAllDescriptor = new TagHelperDescriptor("*", "foo3", "SomeAssembly");
             var descriptors = new TagHelperDescriptor[] { divDescriptor, spanDescriptor, catchAllDescriptor };
             var provider = new TagHelperDescriptorProvider(descriptors);
 
@@ -47,9 +47,9 @@ namespace Microsoft.AspNet.Razor.Test.TagHelpers
         public void TagHelperDescriptorProvider_GetTagHelpersReturnsCatchAllsWithEveryTagName()
         {
             // Arrange
-            var divDescriptor = new TagHelperDescriptor("div", "foo1", "SomeAssembly", ContentBehavior.None);
-            var spanDescriptor = new TagHelperDescriptor("span", "foo2", "SomeAssembly", ContentBehavior.None);
-            var catchAllDescriptor = new TagHelperDescriptor("*", "foo3", "SomeAssembly", ContentBehavior.None);
+            var divDescriptor = new TagHelperDescriptor("div", "foo1", "SomeAssembly");
+            var spanDescriptor = new TagHelperDescriptor("span", "foo2", "SomeAssembly");
+            var catchAllDescriptor = new TagHelperDescriptor("*", "foo3", "SomeAssembly");
             var descriptors = new TagHelperDescriptor[] { divDescriptor, spanDescriptor, catchAllDescriptor };
             var provider = new TagHelperDescriptorProvider(descriptors);
 
@@ -73,7 +73,7 @@ namespace Microsoft.AspNet.Razor.Test.TagHelpers
         public void TagHelperDescriptorProvider_DuplicateDescriptorsAreNotPartOfTagHelperDescriptorPool()
         {
             // Arrange
-            var divDescriptor = new TagHelperDescriptor("div", "foo1", "SomeAssembly", ContentBehavior.None);
+            var divDescriptor = new TagHelperDescriptor("div", "foo1", "SomeAssembly");
             var descriptors = new TagHelperDescriptor[] { divDescriptor, divDescriptor };
             var provider = new TagHelperDescriptorProvider(descriptors);
 

test/Microsoft.AspNet.Razor.Test/TagHelpers/TagHelperParseTreeRewriterTest.cs

@@ -19,6 +19,430 @@ namespace Microsoft.AspNet.Razor.Test.TagHelpers
 {
     public class TagHelperParseTreeRewriterTest : CsHtmlMarkupParserTestBase
     {
+        public static TheoryData<string, MarkupBlock, RazorError[]> MalformedTagHelperAttributeBlockData
+        {
+            get
+            {
+                var factory = CreateDefaultSpanFactory();
+                var blockFactory = new BlockFactory(factory);
+                var errorFormatUnclosed = "Found a malformed '{0}' tag helper. Tag helpers must have a start and " +
+                                          "end tag or be self closing.";
+                var errorFormatNoCloseAngle = "Missing close angle for tag helper '{0}'.";
+                var errorFormatNoCSharp = "The tag helper '{0}' must not have C# in the element's attribute " +
+                                           "declaration area.";
+                Func<string, Block> createInvalidDoBlock = extraCode =>
+                {
+                    return new MarkupBlock(
+                        new MarkupBlock(
+                            new StatementBlock(
+                                factory.CodeTransition(),
+                                factory.Code("do {" + extraCode).AsStatement())));
+                };
+                var dateTimeNow = new MarkupBlock(
+                    new MarkupBlock(
+                        new ExpressionBlock(
+                            factory.CodeTransition(),
+                                factory.Code("DateTime.Now")
+                                    .AsImplicitExpression(CSharpCodeParser.DefaultKeywords)
+                                    .Accepts(AcceptedCharacters.NonWhiteSpace))));
+
+                return new TheoryData<string, MarkupBlock, RazorError[]>
+                {
+                    {
+                        "<p =\"false\"\" ></p>",
+                        new MarkupBlock(
+                            new MarkupTagHelperBlock("p",
+                                new Dictionary<string, SyntaxTreeNode>())),
+                        new []
+                        {
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatUnclosed, "p"),
+                                SourceLocation.Zero)
+                        }
+                    },
+                    {
+                        "<p bar=\"false\"\" <strong>",
+                        new MarkupBlock(
+                            new MarkupTagHelperBlock("p",
+                                new Dictionary<string, SyntaxTreeNode>
+                                {
+                                    { "bar", factory.Markup("false") }
+                                })),
+                        new []
+                        {
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatUnclosed, "p"),
+                                SourceLocation.Zero)
+                        }
+                    },
+                    {
+                        "<p bar='false  <strong>",
+                        new MarkupBlock(
+                            new MarkupTagHelperBlock("p",
+                                new Dictionary<string, SyntaxTreeNode>
+                                {
+                                    { "bar", new MarkupBlock(factory.Markup("false"), factory.Markup("  <strong>")) }
+                                })),
+                        new []
+                        {
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatNoCloseAngle, "p"),
+                                SourceLocation.Zero),
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatUnclosed, "p"),
+                                SourceLocation.Zero)
+                        }
+                    },
+                    {
+                        "<p foo bar<strong>",
+                        new MarkupBlock(
+                            new MarkupTagHelperBlock("p",
+                                new MarkupTagHelperBlock("strong"))),
+                        new []
+                        {
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatNoCloseAngle, "p"),
+                                SourceLocation.Zero),
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatUnclosed, "p"),
+                                SourceLocation.Zero),
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatUnclosed, "strong"),
+                                absoluteIndex: 10, lineIndex: 0, columnIndex: 10)
+                        }
+                    },
+                    {
+                        "<p class=btn\" bar<strong>",
+                        new MarkupBlock(
+                            new MarkupTagHelperBlock("p",
+                                new Dictionary<string, SyntaxTreeNode>
+                                {
+                                    { "class", factory.Markup("btn") }
+                                })),
+                        new []
+                        {
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatUnclosed, "p"),
+                                SourceLocation.Zero)
+                        }
+                    },
+                    {
+                        "<p class=btn\" bar=\"foo\"<strong>",
+                        new MarkupBlock(
+                            new MarkupTagHelperBlock("p",
+                                new Dictionary<string, SyntaxTreeNode>
+                                {
+                                    { "class", factory.Markup("btn") }
+                                })),
+                        new []
+                        {
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatUnclosed, "p"),
+                                SourceLocation.Zero)
+                        }
+                    },
+                    {
+                        "<p class=\"btn bar=\"foo\"<strong>",
+                        new MarkupBlock(
+                            new MarkupTagHelperBlock("p",
+                                new Dictionary<string, SyntaxTreeNode>
+                                {
+                                    { "class", new MarkupBlock(factory.Markup("btn"), factory.Markup(" bar=")) },
+                                    { "foo", factory.Markup(string.Empty) }
+                                },
+                                new MarkupTagHelperBlock("strong"))),
+                        new []
+                        {
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatNoCloseAngle, "p"),
+                                SourceLocation.Zero),
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatUnclosed, "p"),
+                                SourceLocation.Zero),
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatUnclosed, "strong"),
+                                absoluteIndex: 23, lineIndex: 0, columnIndex: 23)
+                        }
+                    },
+                    {
+                        "<p class=\"btn bar=\"foo\"></p>",
+                        new MarkupBlock(
+                            new MarkupTagHelperBlock("p",
+                                new Dictionary<string, SyntaxTreeNode>
+                                {
+                                    { "class", new MarkupBlock(factory.Markup("btn"), factory.Markup(" bar=")) },
+                                })),
+                        new RazorError[0]
+                    },
+                    {
+                        "<p @DateTime.Now class=\"btn\"></p>",
+                        new MarkupBlock(
+                            new MarkupTagHelperBlock("p")),
+                        new []
+                        {
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatNoCSharp, "p"),
+                                absoluteIndex: 3, lineIndex: 0 , columnIndex: 3)
+                        }
+                    },
+                    {
+                        "<p @DateTime.Now=\"btn\"></p>",
+                        new MarkupBlock(
+                            new MarkupTagHelperBlock("p")),
+                        new []
+                        {
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatNoCSharp, "p"),
+                                absoluteIndex: 3, lineIndex: 0 , columnIndex: 3)
+                        }
+                    },
+                    {
+                        "<p class=@DateTime.Now\"></p>",
+                        new MarkupBlock(
+                            new MarkupTagHelperBlock("p",
+                                new Dictionary<string, SyntaxTreeNode>
+                                {
+                                    { "class", dateTimeNow }
+                                })),
+                        new []
+                        {
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatUnclosed, "p"),
+                                SourceLocation.Zero)
+                        }
+                    },
+                    {
+                        "<p class=\"@do {",
+                        new MarkupBlock(
+                            new MarkupTagHelperBlock("p",
+                                new Dictionary<string, SyntaxTreeNode>
+                                {
+                                    { "class", createInvalidDoBlock(string.Empty) }
+                                })),
+                        new []
+                        {
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatNoCloseAngle, "p"),
+                                SourceLocation.Zero),
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatUnclosed, "p"),
+                                SourceLocation.Zero),
+                            new RazorError(
+                                RazorResources.FormatParseError_Expected_EndOfBlock_Before_EOF("do", "}", "{"),
+                                absoluteIndex: 11, lineIndex: 0, columnIndex: 11)
+                        }
+                    },
+                    {
+                        "<p class=\"@do {\"></p>",
+                        new MarkupBlock(
+                            new MarkupTagHelperBlock("p",
+                                new Dictionary<string, SyntaxTreeNode>
+                                {
+                                    { "class", createInvalidDoBlock("\"></p>") }
+                                })),
+                        new []
+                        {
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatNoCloseAngle, "p"),
+                                SourceLocation.Zero),
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatUnclosed, "p"),
+                                SourceLocation.Zero),
+                            new RazorError(
+                                RazorResources.FormatParseError_Expected_EndOfBlock_Before_EOF("do", "}", "{"),
+                                absoluteIndex: 11, lineIndex: 0, columnIndex: 11),
+                            new RazorError(
+                                RazorResources.ParseError_Unterminated_String_Literal,
+                                absoluteIndex: 15, lineIndex: 0, columnIndex: 15)
+                        }
+                    },
+                    {
+                        "<p @do { someattribute=\"btn\"></p>",
+                        new MarkupBlock(
+                            new MarkupTagHelperBlock("p")),
+                        new []
+                        {
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatNoCloseAngle, "p"),
+                                SourceLocation.Zero),
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatUnclosed, "p"),
+                                SourceLocation.Zero),
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatNoCSharp, "p"),
+                                absoluteIndex: 3, lineIndex: 0 , columnIndex: 3),
+                            new RazorError(
+                                RazorResources.FormatParseError_Expected_EndOfBlock_Before_EOF("do", "}", "{"),
+                                absoluteIndex: 4, lineIndex: 0, columnIndex: 4),
+                            new RazorError(
+                                RazorResources.FormatParseError_UnexpectedEndTag("p"),
+                                absoluteIndex: 29, lineIndex: 0, columnIndex: 29)
+                        }
+                    }
+                };
+            }
+        }
+
+        [Theory]
+        [MemberData(nameof(MalformedTagHelperAttributeBlockData))]
+        public void Rewrite_CreatesErrorForMalformedTagHelpersWithAttributes(
+            string documentContent,
+            MarkupBlock expectedOutput,
+            RazorError[] expectedErrors)
+        {
+            RunParseTreeRewriterTest(documentContent, expectedOutput, expectedErrors, "strong", "p");
+        }
+
+        public static TheoryData<string, MarkupBlock, RazorError[]> MalformedTagHelperBlockData
+        {
+            get
+            {
+                var factory = CreateDefaultSpanFactory();
+                var blockFactory = new BlockFactory(factory);
+                var errorFormatUnclosed = "Found a malformed '{0}' tag helper. Tag helpers must have a start and " +
+                                          "end tag or be self closing.";
+                var errorFormatNoCloseAngle = "Missing close angle for tag helper '{0}'.";
+
+                return new TheoryData<string, MarkupBlock, RazorError[]>
+                {
+                    {
+                        "<p",
+                        new MarkupBlock(
+                            new MarkupTagHelperBlock("p")),
+                        new []
+                        {
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatNoCloseAngle, "p"),
+                                SourceLocation.Zero),
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatUnclosed, "p"),
+                                SourceLocation.Zero)
+                        }
+                    },
+                    {
+                        "<p></p",
+                        new MarkupBlock(
+                            new MarkupTagHelperBlock("p")),
+                        new []
+                        {
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatNoCloseAngle, "p"),
+                                absoluteIndex: 3, lineIndex: 0, columnIndex: 3)
+                        }
+                    },
+                    {
+                        "<p><strong",
+                        new MarkupBlock(
+                            new MarkupTagHelperBlock("p",
+                                new MarkupTagHelperBlock("strong"))),
+                        new []
+                        {
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatUnclosed, "p"),
+                                SourceLocation.Zero),
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatNoCloseAngle, "strong"),
+                                absoluteIndex: 3, lineIndex: 0, columnIndex: 3),
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatUnclosed, "strong"),
+                                absoluteIndex: 3, lineIndex: 0, columnIndex: 3)
+                        }
+                    },
+                    {
+                        "<strong <p>",
+                        new MarkupBlock(
+                            new MarkupTagHelperBlock("strong",
+                                new MarkupTagHelperBlock("p"))),
+                        new []
+                        {
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatNoCloseAngle, "strong"),
+                                SourceLocation.Zero),
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatUnclosed, "strong"),
+                                SourceLocation.Zero),
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatUnclosed, "p"),
+                                absoluteIndex: 8, lineIndex: 0, columnIndex: 8)
+                        }
+                    },
+                    {
+                        "<strong </strong",
+                        new MarkupBlock(
+                            new MarkupTagHelperBlock("strong")),
+                        new []
+                        {
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatNoCloseAngle, "strong"),
+                                SourceLocation.Zero),
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatNoCloseAngle, "strong"),
+                                absoluteIndex: 8, lineIndex: 0, columnIndex: 8)
+                        }
+                    },
+                    {
+                        "<<</strong> <<p>",
+                        new MarkupBlock(
+                            blockFactory.MarkupTagBlock("<"),
+                            blockFactory.MarkupTagBlock("<"),
+                            blockFactory.MarkupTagBlock("</strong>"),
+                            factory.Markup(" "),
+                            blockFactory.MarkupTagBlock("<"),
+                            new MarkupTagHelperBlock("p")),
+                        new []
+                        {
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatUnclosed, "strong"),
+                                absoluteIndex: 2, lineIndex: 0, columnIndex: 2),
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatUnclosed, "p"),
+                                absoluteIndex: 13, lineIndex: 0, columnIndex: 13)
+                        }
+                    },
+                    {
+                        "<<<strong>> <<>>",
+                        new MarkupBlock(
+                            blockFactory.MarkupTagBlock("<"),
+                            blockFactory.MarkupTagBlock("<"),
+                            new MarkupTagHelperBlock("strong",
+                                factory.Markup("> "),
+                                blockFactory.MarkupTagBlock("<"),
+                                blockFactory.MarkupTagBlock("<>"),
+                                factory.Markup(">"))),
+                        new []
+                        {
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatUnclosed, "strong"),
+                                absoluteIndex: 2, lineIndex: 0, columnIndex: 2)
+                        }
+                    },
+                    {
+                        "<str<strong></p></strong>",
+                        new MarkupBlock(
+                            blockFactory.MarkupTagBlock("<str"),
+                            new MarkupTagHelperBlock("strong",
+                                blockFactory.MarkupTagBlock("</p>"))),
+                        new []
+                        {
+                            new RazorError(
+                                string.Format(CultureInfo.InvariantCulture, errorFormatUnclosed, "p"),
+                                absoluteIndex: 12, lineIndex: 0, columnIndex: 12)
+                        }
+                    }
+                };
+            }
+        }
+
+        [Theory]
+        [MemberData(nameof(MalformedTagHelperBlockData))]
+        public void Rewrite_CreatesErrorForMalformedTagHelper(
+            string documentContent,
+            MarkupBlock expectedOutput,
+            RazorError[] expectedErrors)
+        {
+            RunParseTreeRewriterTest(documentContent, expectedOutput, expectedErrors, "strong", "p");
+        }
+
         public static TheoryData CodeTagHelperAttributesData
         {
             get
@@ -94,7 +518,7 @@ namespace Microsoft.AspNet.Razor.Test.TagHelpers
             // Arrange
             var descriptors = new TagHelperDescriptor[]
             {
-                new TagHelperDescriptor("person", "PersonTagHelper", "personAssembly", ContentBehavior.None,
+                new TagHelperDescriptor("person", "PersonTagHelper", "personAssembly",
                     attributes: new[]
                     {
                         new TagHelperAttributeDescriptor("age", "Age", typeof(int).FullName),
@@ -105,9 +529,9 @@ namespace Microsoft.AspNet.Razor.Test.TagHelpers
             var providerContext = new TagHelperDescriptorProvider(descriptors);
 
             // Act & Assert
-            EvaluateData(providerContext, 
-                         documentContent, 
-                         expectedOutput, 
+            EvaluateData(providerContext,
+                         documentContent,
+                         expectedOutput,
                          expectedErrors: Enumerable.Empty<RazorError>());
         }
 
@@ -117,8 +541,8 @@ namespace Microsoft.AspNet.Razor.Test.TagHelpers
             {
                 var factory = CreateDefaultSpanFactory();
                 var blockFactory = new BlockFactory(factory);
-                var errorFormat = "Found a malformed '{0}' tag helper. Tag helpers must have a start and end tag or " +
-                                  "be self closing.";
+                var malformedErrorFormat = "Found a malformed '{0}' tag helper. Tag helpers must have a start and " +
+                                           "end tag or be self closing.";
                 var dateTimeNow = new MarkupBlock(
                     new ExpressionBlock(
                         factory.CodeTransition(),
@@ -130,16 +554,23 @@ namespace Microsoft.AspNet.Razor.Test.TagHelpers
                     "<p class=foo dynamic=@DateTime.Now style=color:red;><strong></p></strong>",
                     new MarkupBlock(
                         new MarkupTagHelperBlock("p",
-                        new Dictionary<string, SyntaxTreeNode>
-                        {
-                            { "class", factory.Markup("foo") },
-                            { "dynamic", new MarkupBlock(dateTimeNow) },
-                            { "style", factory.Markup("color:red;") }
-                        },
-                        new MarkupTagHelperBlock("strong",
-                            blockFactory.MarkupTagBlock("</p>")))),
-                    new RazorError(string.Format(CultureInfo.InvariantCulture, errorFormat, "p"),
-                                   SourceLocation.Zero)
+                            new Dictionary<string, SyntaxTreeNode>
+                            {
+                                { "class", factory.Markup("foo") },
+                                { "dynamic", new MarkupBlock(dateTimeNow) },
+                                { "style", factory.Markup("color:red;") }
+                            },
+                            new MarkupTagHelperBlock("strong")),
+                            blockFactory.MarkupTagBlock("</strong>")),
+                    new RazorError[]
+                    {
+                        new RazorError(
+                            string.Format(CultureInfo.InvariantCulture, malformedErrorFormat, "strong"),
+                            absoluteIndex: 52, lineIndex: 0, columnIndex: 52),
+                        new RazorError(
+                            string.Format(CultureInfo.InvariantCulture, malformedErrorFormat, "strong"),
+                            absoluteIndex: 64, lineIndex: 0, columnIndex: 64)
+                    }
                 };
                 yield return new object[] {
                     "<div><p>Hello <strong>World</strong></div>",
@@ -150,8 +581,12 @@ namespace Microsoft.AspNet.Razor.Test.TagHelpers
                             new MarkupTagHelperBlock("strong",
                                 factory.Markup("World")),
                             blockFactory.MarkupTagBlock("</div>"))),
-                    new RazorError(string.Format(CultureInfo.InvariantCulture, errorFormat, "p"),
-                                   absoluteIndex: 5, lineIndex: 0, columnIndex: 5)
+                    new RazorError[]
+                    {
+                        new RazorError(
+                            string.Format(CultureInfo.InvariantCulture, malformedErrorFormat, "p"),
+                            absoluteIndex: 5, lineIndex: 0, columnIndex: 5)
+                    }
                 };
                 yield return new object[] {
                     "<div><p>Hello <strong>World</div>",
@@ -162,8 +597,15 @@ namespace Microsoft.AspNet.Razor.Test.TagHelpers
                             new MarkupTagHelperBlock("strong",
                                 factory.Markup("World"),
                                 blockFactory.MarkupTagBlock("</div>")))),
-                    new RazorError(string.Format(CultureInfo.InvariantCulture, errorFormat, "strong"),
-                                   absoluteIndex: 14, lineIndex: 0, columnIndex: 14)
+                    new RazorError[]
+                    {
+                        new RazorError(
+                            string.Format(CultureInfo.InvariantCulture, malformedErrorFormat, "p"),
+                            absoluteIndex: 5, lineIndex: 0, columnIndex: 5),
+                        new RazorError(
+                            string.Format(CultureInfo.InvariantCulture, malformedErrorFormat, "strong"),
+                            absoluteIndex: 14, lineIndex: 0, columnIndex: 14)
+                    }
                 };
                 yield return new object[] {
                     "<p class=\"foo\">Hello <p style=\"color:red;\">World</p>",
@@ -180,8 +622,12 @@ namespace Microsoft.AspNet.Razor.Test.TagHelpers
                                     { "style", factory.Markup("color:red;") }
                                 },
                                 factory.Markup("World")))),
-                    new RazorError(string.Format(CultureInfo.InvariantCulture, errorFormat, "p"),
-                                   SourceLocation.Zero)
+                    new RazorError[]
+                    {
+                        new RazorError(
+                            string.Format(CultureInfo.InvariantCulture, malformedErrorFormat, "p"),
+                            SourceLocation.Zero)
+                    }
                 };
             }
         }
@@ -191,9 +637,9 @@ namespace Microsoft.AspNet.Razor.Test.TagHelpers
         public void TagHelperParseTreeRewriter_CreatesErrorForIncompleteTagHelper(
             string documentContent,
             MarkupBlock expectedOutput,
-            RazorError expectedError)
+            RazorError[] expectedErrors)
         {
-            RunParseTreeRewriterTest(documentContent, expectedOutput, new[] { expectedError }, "strong", "p");
+            RunParseTreeRewriterTest(documentContent, expectedOutput, expectedErrors, "strong", "p");
         }
 
         public static TheoryData<string, MarkupBlock> InvalidHtmlBlockData
@@ -1268,7 +1714,7 @@ namespace Microsoft.AspNet.Razor.Test.TagHelpers
             foreach (var tagName in tagNames)
             {
                 descriptors.Add(
-                    new TagHelperDescriptor(tagName, tagName + "taghelper", "SomeAssembly", ContentBehavior.None));
+                    new TagHelperDescriptor(tagName, tagName + "taghelper", "SomeAssembly"));
             }
 
             return new TagHelperDescriptorProvider(descriptors);
@@ -1292,8 +1738,10 @@ namespace Microsoft.AspNet.Razor.Test.TagHelpers
             var rewritingContext = new RewritingContext(results.Document, errorSink);
             new TagHelperParseTreeRewriter(provider).Rewrite(rewritingContext);
             var rewritten = rewritingContext.SyntaxTree;
+            var actualErrors = errorSink.Errors.OrderBy(error => error.Location.AbsoluteIndex)
+                                               .ToList();
 
-            EvaluateRazorErrors(errorSink.Errors.ToList(), expectedErrors.ToList());
+            EvaluateRazorErrors(actualErrors, expectedErrors.ToList());
             EvaluateParseTree(rewritten, expectedOutput);
         }
 

test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/CS/Output/BasicTagHelpers.CustomAttributeCodeGenerator.cs

@@ -7,7 +7,9 @@ namespace TestOutput
     public class BasicTagHelpers
     {
         #line hidden
+        #pragma warning disable 0414
         private System.IO.TextWriter __tagHelperStringValueBuffer = null;
+        #pragma warning restore 0414
         private TagHelperExecutionContext __tagHelperExecutionContext = null;
         private TagHelperRunner __tagHelperRunner = new TagHelperRunner();
         private TagHelperScopeManager __tagHelperScopeManager = new TagHelperScopeManager();
@@ -25,57 +27,117 @@ namespace TestOutput
             Instrumentation.BeginContext(27, 49, true);
             WriteLiteral("\r\n<div class=\"randomNonTagHelperAttribute\">\r\n    ");
             Instrumentation.EndContext();
-            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("p");
+            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("p", "test", async() => {
+                WriteLiteral("\r\n        ");
+                __tagHelperExecutionContext = __tagHelperScopeManager.Begin("p", "test", async() => {
+                }
+                , StartWritingScope, EndWritingScope);
+                __PTagHelper = CreateTagHelper<PTagHelper>();
+                __tagHelperExecutionContext.Add(__PTagHelper);
+                __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
+                if (__tagHelperExecutionContext.Output.ContentSet)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+                }
+                else if (__tagHelperExecutionContext.ChildContentRetrieved)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+                }
+                else
+                {
+                    __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+                }
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
+                __tagHelperExecutionContext = __tagHelperScopeManager.End();
+                WriteLiteral("\r\n        ");
+                __tagHelperExecutionContext = __tagHelperScopeManager.Begin("input", "test", async() => {
+                }
+                , StartWritingScope, EndWritingScope);
+                __InputTagHelper = CreateTagHelper<InputTagHelper>();
+                __tagHelperExecutionContext.Add(__InputTagHelper);
+                __InputTagHelper.Type = **From custom attribute code renderer**: "text";
+                __tagHelperExecutionContext.AddTagHelperAttribute("type", __InputTagHelper.Type);
+                __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
+                __tagHelperExecutionContext.Add(__InputTagHelper2);
+                __InputTagHelper2.Type = __InputTagHelper.Type;
+                __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
+                if (__tagHelperExecutionContext.Output.ContentSet)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+                }
+                else if (__tagHelperExecutionContext.ChildContentRetrieved)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+                }
+                else
+                {
+                    __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+                }
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
+                __tagHelperExecutionContext = __tagHelperScopeManager.End();
+                WriteLiteral("\r\n        ");
+                __tagHelperExecutionContext = __tagHelperScopeManager.Begin("input", "test", async() => {
+                }
+                , StartWritingScope, EndWritingScope);
+                __InputTagHelper = CreateTagHelper<InputTagHelper>();
+                __tagHelperExecutionContext.Add(__InputTagHelper);
+                __InputTagHelper.Type = **From custom attribute code renderer**: "checkbox";
+                __tagHelperExecutionContext.AddTagHelperAttribute("type", __InputTagHelper.Type);
+                __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
+                __tagHelperExecutionContext.Add(__InputTagHelper2);
+                __InputTagHelper2.Type = __InputTagHelper.Type;
+#line 7 "BasicTagHelpers.cshtml"
+            __InputTagHelper2.Checked = **From custom attribute code renderer**: true;
+
+#line default
+#line hidden
+                __tagHelperExecutionContext.AddTagHelperAttribute("checked", __InputTagHelper2.Checked);
+                __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
+                if (__tagHelperExecutionContext.Output.ContentSet)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+                }
+                else if (__tagHelperExecutionContext.ChildContentRetrieved)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+                }
+                else
+                {
+                    __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+                }
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
+                __tagHelperExecutionContext = __tagHelperScopeManager.End();
+                WriteLiteral("\r\n    ");
+            }
+            , StartWritingScope, EndWritingScope);
             __PTagHelper = CreateTagHelper<PTagHelper>();
             __tagHelperExecutionContext.Add(__PTagHelper);
             __tagHelperExecutionContext.AddHtmlAttribute("class", "Hello World");
             __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
             WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
-            Instrumentation.BeginContext(99, 10, true);
-            WriteLiteral("\r\n        ");
-            Instrumentation.EndContext();
-            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("p");
-            __PTagHelper = CreateTagHelper<PTagHelper>();
-            __tagHelperExecutionContext.Add(__PTagHelper);
-            __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
-            __tagHelperExecutionContext = __tagHelperScopeManager.End();
-            Instrumentation.BeginContext(116, 10, true);
-            WriteLiteral("\r\n        ");
-            Instrumentation.EndContext();
-            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("input");
-            __InputTagHelper = CreateTagHelper<InputTagHelper>();
-            __tagHelperExecutionContext.Add(__InputTagHelper);
-            __InputTagHelper.Type = **From custom attribute code renderer**: "text";
-            __tagHelperExecutionContext.AddTagHelperAttribute("type", __InputTagHelper.Type);
-            __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
-            __tagHelperExecutionContext.Add(__InputTagHelper2);
-            __InputTagHelper2.Type = __InputTagHelper.Type;
-            __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
-            __tagHelperExecutionContext = __tagHelperScopeManager.End();
-            Instrumentation.BeginContext(147, 10, true);
-            WriteLiteral("\r\n        ");
-            Instrumentation.EndContext();
-            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("input");
-            __InputTagHelper = CreateTagHelper<InputTagHelper>();
-            __tagHelperExecutionContext.Add(__InputTagHelper);
-            __InputTagHelper.Type = **From custom attribute code renderer**: "checkbox";
-            __tagHelperExecutionContext.AddTagHelperAttribute("type", __InputTagHelper.Type);
-            __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
-            __tagHelperExecutionContext.Add(__InputTagHelper2);
-            __InputTagHelper2.Type = __InputTagHelper.Type;
-            __InputTagHelper2.Checked = **From custom attribute code renderer**: true;
-            __tagHelperExecutionContext.AddTagHelperAttribute("checked", __InputTagHelper2.Checked);
-            __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
-            __tagHelperExecutionContext = __tagHelperScopeManager.End();
-            Instrumentation.BeginContext(196, 6, true);
-            WriteLiteral("\r\n    ");
-            Instrumentation.EndContext();
+            WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
+            if (__tagHelperExecutionContext.Output.ContentSet)
+            {
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+            }
+            else if (__tagHelperExecutionContext.ChildContentRetrieved)
+            {
+                WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+            }
+            else
+            {
+                __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+            }
+            WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
             WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
             __tagHelperExecutionContext = __tagHelperScopeManager.End();
             Instrumentation.BeginContext(206, 8, true);

test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/CS/Output/BasicTagHelpers.DesignTime.cs

@@ -32,7 +32,6 @@ namespace TestOutput
         #pragma warning disable 1998
         public override async Task ExecuteAsync()
         {
-            __PTagHelper = CreateTagHelper<PTagHelper>();
             __PTagHelper = CreateTagHelper<PTagHelper>();
             __InputTagHelper = CreateTagHelper<InputTagHelper>();
             __InputTagHelper.Type = "text";
@@ -42,7 +41,12 @@ namespace TestOutput
             __InputTagHelper.Type = "checkbox";
             __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
             __InputTagHelper2.Type = __InputTagHelper.Type;
+#line 7 "BasicTagHelpers.cshtml"
             __InputTagHelper2.Checked = true;
+
+#line default
+#line hidden
+            __PTagHelper = CreateTagHelper<PTagHelper>();
         }
         #pragma warning restore 1998
     }

test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/CS/Output/BasicTagHelpers.cs

@@ -8,7 +8,9 @@ namespace TestOutput
     public class BasicTagHelpers
     {
         #line hidden
+        #pragma warning disable 0414
         private System.IO.TextWriter __tagHelperStringValueBuffer = null;
+        #pragma warning restore 0414
         private TagHelperExecutionContext __tagHelperExecutionContext = null;
         private TagHelperRunner __tagHelperRunner = new TagHelperRunner();
         private TagHelperScopeManager __tagHelperScopeManager = new TagHelperScopeManager();
@@ -26,57 +28,117 @@ namespace TestOutput
             Instrumentation.BeginContext(27, 49, true);
             WriteLiteral("\r\n<div class=\"randomNonTagHelperAttribute\">\r\n    ");
             Instrumentation.EndContext();
-            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("p");
+            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("p", "test", async() => {
+                WriteLiteral("\r\n        ");
+                __tagHelperExecutionContext = __tagHelperScopeManager.Begin("p", "test", async() => {
+                }
+                , StartWritingScope, EndWritingScope);
+                __PTagHelper = CreateTagHelper<PTagHelper>();
+                __tagHelperExecutionContext.Add(__PTagHelper);
+                __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
+                if (__tagHelperExecutionContext.Output.ContentSet)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+                }
+                else if (__tagHelperExecutionContext.ChildContentRetrieved)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+                }
+                else
+                {
+                    __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+                }
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
+                __tagHelperExecutionContext = __tagHelperScopeManager.End();
+                WriteLiteral("\r\n        ");
+                __tagHelperExecutionContext = __tagHelperScopeManager.Begin("input", "test", async() => {
+                }
+                , StartWritingScope, EndWritingScope);
+                __InputTagHelper = CreateTagHelper<InputTagHelper>();
+                __tagHelperExecutionContext.Add(__InputTagHelper);
+                __InputTagHelper.Type = "text";
+                __tagHelperExecutionContext.AddTagHelperAttribute("type", __InputTagHelper.Type);
+                __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
+                __tagHelperExecutionContext.Add(__InputTagHelper2);
+                __InputTagHelper2.Type = __InputTagHelper.Type;
+                __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
+                if (__tagHelperExecutionContext.Output.ContentSet)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+                }
+                else if (__tagHelperExecutionContext.ChildContentRetrieved)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+                }
+                else
+                {
+                    __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+                }
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
+                __tagHelperExecutionContext = __tagHelperScopeManager.End();
+                WriteLiteral("\r\n        ");
+                __tagHelperExecutionContext = __tagHelperScopeManager.Begin("input", "test", async() => {
+                }
+                , StartWritingScope, EndWritingScope);
+                __InputTagHelper = CreateTagHelper<InputTagHelper>();
+                __tagHelperExecutionContext.Add(__InputTagHelper);
+                __InputTagHelper.Type = "checkbox";
+                __tagHelperExecutionContext.AddTagHelperAttribute("type", __InputTagHelper.Type);
+                __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
+                __tagHelperExecutionContext.Add(__InputTagHelper2);
+                __InputTagHelper2.Type = __InputTagHelper.Type;
+#line 7 "BasicTagHelpers.cshtml"
+            __InputTagHelper2.Checked = true;
+
+#line default
+#line hidden
+                __tagHelperExecutionContext.AddTagHelperAttribute("checked", __InputTagHelper2.Checked);
+                __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
+                if (__tagHelperExecutionContext.Output.ContentSet)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+                }
+                else if (__tagHelperExecutionContext.ChildContentRetrieved)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+                }
+                else
+                {
+                    __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+                }
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
+                __tagHelperExecutionContext = __tagHelperScopeManager.End();
+                WriteLiteral("\r\n    ");
+            }
+            , StartWritingScope, EndWritingScope);
             __PTagHelper = CreateTagHelper<PTagHelper>();
             __tagHelperExecutionContext.Add(__PTagHelper);
             __tagHelperExecutionContext.AddHtmlAttribute("class", "Hello World");
             __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
             WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
-            Instrumentation.BeginContext(99, 10, true);
-            WriteLiteral("\r\n        ");
-            Instrumentation.EndContext();
-            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("p");
-            __PTagHelper = CreateTagHelper<PTagHelper>();
-            __tagHelperExecutionContext.Add(__PTagHelper);
-            __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
-            __tagHelperExecutionContext = __tagHelperScopeManager.End();
-            Instrumentation.BeginContext(116, 10, true);
-            WriteLiteral("\r\n        ");
-            Instrumentation.EndContext();
-            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("input");
-            __InputTagHelper = CreateTagHelper<InputTagHelper>();
-            __tagHelperExecutionContext.Add(__InputTagHelper);
-            __InputTagHelper.Type = "text";
-            __tagHelperExecutionContext.AddTagHelperAttribute("type", __InputTagHelper.Type);
-            __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
-            __tagHelperExecutionContext.Add(__InputTagHelper2);
-            __InputTagHelper2.Type = __InputTagHelper.Type;
-            __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
-            __tagHelperExecutionContext = __tagHelperScopeManager.End();
-            Instrumentation.BeginContext(147, 10, true);
-            WriteLiteral("\r\n        ");
-            Instrumentation.EndContext();
-            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("input");
-            __InputTagHelper = CreateTagHelper<InputTagHelper>();
-            __tagHelperExecutionContext.Add(__InputTagHelper);
-            __InputTagHelper.Type = "checkbox";
-            __tagHelperExecutionContext.AddTagHelperAttribute("type", __InputTagHelper.Type);
-            __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
-            __tagHelperExecutionContext.Add(__InputTagHelper2);
-            __InputTagHelper2.Type = __InputTagHelper.Type;
-            __InputTagHelper2.Checked = true;
-            __tagHelperExecutionContext.AddTagHelperAttribute("checked", __InputTagHelper2.Checked);
-            __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
-            __tagHelperExecutionContext = __tagHelperScopeManager.End();
-            Instrumentation.BeginContext(196, 6, true);
-            WriteLiteral("\r\n    ");
-            Instrumentation.EndContext();
+            WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
+            if (__tagHelperExecutionContext.Output.ContentSet)
+            {
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+            }
+            else if (__tagHelperExecutionContext.ChildContentRetrieved)
+            {
+                WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+            }
+            else
+            {
+                __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+            }
+            WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
             WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
             __tagHelperExecutionContext = __tagHelperScopeManager.End();
             Instrumentation.BeginContext(206, 8, true);

test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/CS/Output/ComplexTagHelpers.DesignTime.cs

@@ -41,12 +41,6 @@ if (true)
 #line default
 #line hidden
 
-            __PTagHelper = CreateTagHelper<PTagHelper>();
-#line 8 "ComplexTagHelpers.cshtml"
-__o = DateTime.Now;
-
-#line default
-#line hidden
 #line 10 "ComplexTagHelpers.cshtml"
             
 
@@ -60,11 +54,11 @@ __o = DateTime.Now;
 #line default
 #line hidden
 
-            __PTagHelper = CreateTagHelper<PTagHelper>();
             __InputTagHelper = CreateTagHelper<InputTagHelper>();
             __InputTagHelper.Type = "text";
             __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
             __InputTagHelper2.Type = __InputTagHelper.Type;
+            __PTagHelper = CreateTagHelper<PTagHelper>();
 #line 13 "ComplexTagHelpers.cshtml"
             }
             else
@@ -73,7 +67,6 @@ __o = DateTime.Now;
 #line default
 #line hidden
 
-            __PTagHelper = CreateTagHelper<PTagHelper>();
             __InputTagHelper = CreateTagHelper<InputTagHelper>();
 #line 16 "ComplexTagHelpers.cshtml"
 __o = checkbox;
@@ -83,7 +76,12 @@ __o = checkbox;
             __InputTagHelper.Type = string.Empty;
             __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
             __InputTagHelper2.Type = __InputTagHelper.Type;
-            __InputTagHelper2.Checked = true;
+#line 16 "ComplexTagHelpers.cshtml"
+                                   __InputTagHelper2.Checked = true;
+
+#line default
+#line hidden
+            __PTagHelper = CreateTagHelper<PTagHelper>();
             __InputTagHelper = CreateTagHelper<InputTagHelper>();
 #line 17 "ComplexTagHelpers.cshtml"
 __o = true ? "checkbox" : "anything";
@@ -121,7 +119,77 @@ if(true) {
 #line default
 #line hidden
 
+            __PTagHelper = CreateTagHelper<PTagHelper>();
+#line 8 "ComplexTagHelpers.cshtml"
+__o = DateTime.Now;
+
+#line default
+#line hidden
 #line 22 "ComplexTagHelpers.cshtml"
+            
+
+#line default
+#line hidden
+
+#line 22 "ComplexTagHelpers.cshtml"
+               var @object = false;
+
+#line default
+#line hidden
+
+            __InputTagHelper = CreateTagHelper<InputTagHelper>();
+            __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
+#line 23 "ComplexTagHelpers.cshtml"
+__InputTagHelper2.Checked = @object;
+
+#line default
+#line hidden
+            __PTagHelper = CreateTagHelper<PTagHelper>();
+#line 21 "ComplexTagHelpers.cshtml"
+__PTagHelper.Age = DateTimeOffset.Now.Year - 1970;
+
+#line default
+#line hidden
+            __InputTagHelper = CreateTagHelper<InputTagHelper>();
+            __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
+#line 26 "ComplexTagHelpers.cshtml"
+__InputTagHelper2.Checked = DateTimeOffset.Now.Year > 2014;
+
+#line default
+#line hidden
+            __PTagHelper = CreateTagHelper<PTagHelper>();
+#line 25 "ComplexTagHelpers.cshtml"
+__PTagHelper.Age = -1970 + DateTimeOffset.Now.Year;
+
+#line default
+#line hidden
+            __InputTagHelper = CreateTagHelper<InputTagHelper>();
+            __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
+#line 29 "ComplexTagHelpers.cshtml"
+__InputTagHelper2.Checked = DateTimeOffset.Now.Year > 2014;
+
+#line default
+#line hidden
+            __PTagHelper = CreateTagHelper<PTagHelper>();
+#line 28 "ComplexTagHelpers.cshtml"
+__PTagHelper.Age = DateTimeOffset.Now.Year - 1970;
+
+#line default
+#line hidden
+            __InputTagHelper = CreateTagHelper<InputTagHelper>();
+            __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
+#line 32 "ComplexTagHelpers.cshtml"
+__InputTagHelper2.Checked =      DateTimeOffset.Now.Year   > 2014   ;
+
+#line default
+#line hidden
+            __PTagHelper = CreateTagHelper<PTagHelper>();
+#line 31 "ComplexTagHelpers.cshtml"
+__PTagHelper.Age = "My age is this long.".Length;
+
+#line default
+#line hidden
+#line 35 "ComplexTagHelpers.cshtml"
 }
 
 #line default

test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/CS/Output/ComplexTagHelpers.cs

@@ -1,4 +1,4 @@
-#pragma checksum "ComplexTagHelpers.cshtml" "{ff1816ec-aa5e-4d10-87f7-6f4963833460}" "cce31144cd1c3c35d241b49e41c4fc04ff044565"
+#pragma checksum "ComplexTagHelpers.cshtml" "{ff1816ec-aa5e-4d10-87f7-6f4963833460}" "7158abc69d261099393d49d82670ec64a94d9770"
 namespace TestOutput
 {
     using Microsoft.AspNet.Razor.Runtime.TagHelpers;
@@ -8,7 +8,9 @@ namespace TestOutput
     public class ComplexTagHelpers
     {
         #line hidden
+        #pragma warning disable 0414
         private System.IO.TextWriter __tagHelperStringValueBuffer = null;
+        #pragma warning restore 0414
         private TagHelperExecutionContext __tagHelperExecutionContext = null;
         private TagHelperRunner __tagHelperRunner = new TagHelperRunner();
         private TagHelperScopeManager __tagHelperScopeManager = new TagHelperScopeManager();
@@ -38,23 +40,8 @@ namespace TestOutput
             Instrumentation.BeginContext(78, 55, true);
             WriteLiteral("    <div class=\"randomNonTagHelperAttribute\">\r\n        ");
             Instrumentation.EndContext();
-            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("p");
-            __PTagHelper = CreateTagHelper<PTagHelper>();
-            __tagHelperExecutionContext.Add(__PTagHelper);
-            StartWritingScope();
-            WriteLiteral("Current Time: ");
-#line 8 "ComplexTagHelpers.cshtml"
-Write(DateTime.Now);
-
-#line default
-#line hidden
-            __tagHelperStringValueBuffer = EndWritingScope();
-            __tagHelperExecutionContext.AddHtmlAttribute("time", __tagHelperStringValueBuffer.ToString());
-            __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
-            Instrumentation.BeginContext(171, 34, true);
-            WriteLiteral("\r\n            <h1>Set Time:</h1>\r\n");
-            Instrumentation.EndContext();
+            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("p", "test", async() => {
+                WriteLiteral("\r\n            <h1>Set Time:</h1>\r\n");
 #line 10 "ComplexTagHelpers.cshtml"
             
 
@@ -68,36 +55,62 @@ Write(DateTime.Now);
 #line default
 #line hidden
 
-            Instrumentation.BeginContext(245, 16, true);
-            WriteLiteral("                ");
-            Instrumentation.EndContext();
-            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("p");
-            __PTagHelper = CreateTagHelper<PTagHelper>();
-            __tagHelperExecutionContext.Add(__PTagHelper);
-            __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
-            Instrumentation.BeginContext(264, 10, true);
-            WriteLiteral("New Time: ");
-            Instrumentation.EndContext();
-            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("input");
-            __InputTagHelper = CreateTagHelper<InputTagHelper>();
-            __tagHelperExecutionContext.Add(__InputTagHelper);
-            __InputTagHelper.Type = "text";
-            __tagHelperExecutionContext.AddTagHelperAttribute("type", __InputTagHelper.Type);
-            __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
-            __tagHelperExecutionContext.Add(__InputTagHelper2);
-            __InputTagHelper2.Type = __InputTagHelper.Type;
-            __tagHelperExecutionContext.AddHtmlAttribute("value", "");
-            __tagHelperExecutionContext.AddHtmlAttribute("placeholder", "Enter in a new time...");
-            __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
-            __tagHelperExecutionContext = __tagHelperScopeManager.End();
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
-            __tagHelperExecutionContext = __tagHelperScopeManager.End();
-            Instrumentation.BeginContext(344, 2, true);
-            WriteLiteral("\r\n");
-            Instrumentation.EndContext();
+                WriteLiteral("                ");
+                __tagHelperExecutionContext = __tagHelperScopeManager.Begin("p", "test", async() => {
+                    WriteLiteral("New Time: ");
+                    __tagHelperExecutionContext = __tagHelperScopeManager.Begin("input", "test", async() => {
+                    }
+                    , StartWritingScope, EndWritingScope);
+                    __InputTagHelper = CreateTagHelper<InputTagHelper>();
+                    __tagHelperExecutionContext.Add(__InputTagHelper);
+                    __InputTagHelper.Type = "text";
+                    __tagHelperExecutionContext.AddTagHelperAttribute("type", __InputTagHelper.Type);
+                    __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
+                    __tagHelperExecutionContext.Add(__InputTagHelper2);
+                    __InputTagHelper2.Type = __InputTagHelper.Type;
+                    __tagHelperExecutionContext.AddHtmlAttribute("value", "");
+                    __tagHelperExecutionContext.AddHtmlAttribute("placeholder", "Enter in a new time...");
+                    __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
+                    WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
+                    WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
+                    if (__tagHelperExecutionContext.Output.ContentSet)
+                    {
+                        WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+                    }
+                    else if (__tagHelperExecutionContext.ChildContentRetrieved)
+                    {
+                        WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+                    }
+                    else
+                    {
+                        __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+                    }
+                    WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
+                    WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
+                    __tagHelperExecutionContext = __tagHelperScopeManager.End();
+                }
+                , StartWritingScope, EndWritingScope);
+                __PTagHelper = CreateTagHelper<PTagHelper>();
+                __tagHelperExecutionContext.Add(__PTagHelper);
+                __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
+                if (__tagHelperExecutionContext.Output.ContentSet)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+                }
+                else if (__tagHelperExecutionContext.ChildContentRetrieved)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+                }
+                else
+                {
+                    __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+                }
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
+                __tagHelperExecutionContext = __tagHelperScopeManager.End();
+                WriteLiteral("\r\n");
 #line 13 "ComplexTagHelpers.cshtml"
             }
             else
@@ -106,117 +119,475 @@ Write(DateTime.Now);
 #line default
 #line hidden
 
-            Instrumentation.BeginContext(394, 16, true);
-            WriteLiteral("                ");
-            Instrumentation.EndContext();
-            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("p");
-            __PTagHelper = CreateTagHelper<PTagHelper>();
-            __tagHelperExecutionContext.Add(__PTagHelper);
-            __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
-            Instrumentation.BeginContext(413, 14, true);
-            WriteLiteral("Current Time: ");
-            Instrumentation.EndContext();
-            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("input");
-            __InputTagHelper = CreateTagHelper<InputTagHelper>();
-            __tagHelperExecutionContext.Add(__InputTagHelper);
-            StartWritingScope();
+                WriteLiteral("                ");
+                __tagHelperExecutionContext = __tagHelperScopeManager.Begin("p", "test", async() => {
+                    WriteLiteral("Current Time: ");
+                    __tagHelperExecutionContext = __tagHelperScopeManager.Begin("input", "test", async() => {
+                    }
+                    , StartWritingScope, EndWritingScope);
+                    __InputTagHelper = CreateTagHelper<InputTagHelper>();
+                    __tagHelperExecutionContext.Add(__InputTagHelper);
+                    StartWritingScope();
 #line 16 "ComplexTagHelpers.cshtml"
 Write(checkbox);
 
 #line default
 #line hidden
-            __tagHelperStringValueBuffer = EndWritingScope();
-            __InputTagHelper.Type = __tagHelperStringValueBuffer.ToString();
-            __tagHelperExecutionContext.AddTagHelperAttribute("type", __InputTagHelper.Type);
-            __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
-            __tagHelperExecutionContext.Add(__InputTagHelper2);
-            __InputTagHelper2.Type = __InputTagHelper.Type;
-            __InputTagHelper2.Checked = true;
-            __tagHelperExecutionContext.AddTagHelperAttribute("checked", __InputTagHelper2.Checked);
-            __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
-            __tagHelperExecutionContext = __tagHelperScopeManager.End();
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
-            __tagHelperExecutionContext = __tagHelperScopeManager.End();
-            Instrumentation.BeginContext(468, 18, true);
-            WriteLiteral("\r\n                ");
-            Instrumentation.EndContext();
-            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("input");
-            __InputTagHelper = CreateTagHelper<InputTagHelper>();
-            __tagHelperExecutionContext.Add(__InputTagHelper);
-            StartWritingScope();
+                    __tagHelperStringValueBuffer = EndWritingScope();
+                    __InputTagHelper.Type = __tagHelperStringValueBuffer.ToString();
+                    __tagHelperExecutionContext.AddTagHelperAttribute("type", __InputTagHelper.Type);
+                    __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
+                    __tagHelperExecutionContext.Add(__InputTagHelper2);
+                    __InputTagHelper2.Type = __InputTagHelper.Type;
+#line 16 "ComplexTagHelpers.cshtml"
+                                   __InputTagHelper2.Checked = true;
+
+#line default
+#line hidden
+                    __tagHelperExecutionContext.AddTagHelperAttribute("checked", __InputTagHelper2.Checked);
+                    __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
+                    WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
+                    WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
+                    if (__tagHelperExecutionContext.Output.ContentSet)
+                    {
+                        WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+                    }
+                    else if (__tagHelperExecutionContext.ChildContentRetrieved)
+                    {
+                        WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+                    }
+                    else
+                    {
+                        __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+                    }
+                    WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
+                    WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
+                    __tagHelperExecutionContext = __tagHelperScopeManager.End();
+                }
+                , StartWritingScope, EndWritingScope);
+                __PTagHelper = CreateTagHelper<PTagHelper>();
+                __tagHelperExecutionContext.Add(__PTagHelper);
+                __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
+                if (__tagHelperExecutionContext.Output.ContentSet)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+                }
+                else if (__tagHelperExecutionContext.ChildContentRetrieved)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+                }
+                else
+                {
+                    __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+                }
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
+                __tagHelperExecutionContext = __tagHelperScopeManager.End();
+                WriteLiteral("\r\n                ");
+                __tagHelperExecutionContext = __tagHelperScopeManager.Begin("input", "test", async() => {
+                }
+                , StartWritingScope, EndWritingScope);
+                __InputTagHelper = CreateTagHelper<InputTagHelper>();
+                __tagHelperExecutionContext.Add(__InputTagHelper);
+                StartWritingScope();
 #line 17 "ComplexTagHelpers.cshtml"
 Write(true ? "checkbox" : "anything");
 
 #line default
 #line hidden
-            __tagHelperStringValueBuffer = EndWritingScope();
-            __InputTagHelper.Type = __tagHelperStringValueBuffer.ToString();
-            __tagHelperExecutionContext.AddTagHelperAttribute("type", __InputTagHelper.Type);
-            __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
-            __tagHelperExecutionContext.Add(__InputTagHelper2);
-            __InputTagHelper2.Type = __InputTagHelper.Type;
-            __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
-            __tagHelperExecutionContext = __tagHelperScopeManager.End();
-            Instrumentation.BeginContext(536, 18, true);
-            WriteLiteral("\r\n                ");
-            Instrumentation.EndContext();
-            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("input");
-            __InputTagHelper = CreateTagHelper<InputTagHelper>();
-            __tagHelperExecutionContext.Add(__InputTagHelper);
-            StartWritingScope();
+                __tagHelperStringValueBuffer = EndWritingScope();
+                __InputTagHelper.Type = __tagHelperStringValueBuffer.ToString();
+                __tagHelperExecutionContext.AddTagHelperAttribute("type", __InputTagHelper.Type);
+                __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
+                __tagHelperExecutionContext.Add(__InputTagHelper2);
+                __InputTagHelper2.Type = __InputTagHelper.Type;
+                __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
+                if (__tagHelperExecutionContext.Output.ContentSet)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+                }
+                else if (__tagHelperExecutionContext.ChildContentRetrieved)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+                }
+                else
+                {
+                    __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+                }
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
+                __tagHelperExecutionContext = __tagHelperScopeManager.End();
+                WriteLiteral("\r\n                ");
+                __tagHelperExecutionContext = __tagHelperScopeManager.Begin("input", "test", async() => {
+                }
+                , StartWritingScope, EndWritingScope);
+                __InputTagHelper = CreateTagHelper<InputTagHelper>();
+                __tagHelperExecutionContext.Add(__InputTagHelper);
+                StartWritingScope();
 #line 18 "ComplexTagHelpers.cshtml"
 if(true) {
 
 #line default
 #line hidden
 
-            WriteLiteral(" checkbox ");
+                WriteLiteral(" checkbox ");
 #line 18 "ComplexTagHelpers.cshtml"
 } else {
 
 #line default
 #line hidden
 
-            WriteLiteral(" anything ");
+                WriteLiteral(" anything ");
 #line 18 "ComplexTagHelpers.cshtml"
 }
 
 #line default
 #line hidden
 
-            __tagHelperStringValueBuffer = EndWritingScope();
-            __InputTagHelper.Type = __tagHelperStringValueBuffer.ToString();
-            __tagHelperExecutionContext.AddTagHelperAttribute("type", __InputTagHelper.Type);
-            __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
-            __tagHelperExecutionContext.Add(__InputTagHelper2);
-            __InputTagHelper2.Type = __InputTagHelper.Type;
-            __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
-            __tagHelperExecutionContext = __tagHelperScopeManager.End();
-            Instrumentation.BeginContext(637, 2, true);
-            WriteLiteral("\r\n");
-            Instrumentation.EndContext();
+                __tagHelperStringValueBuffer = EndWritingScope();
+                __InputTagHelper.Type = __tagHelperStringValueBuffer.ToString();
+                __tagHelperExecutionContext.AddTagHelperAttribute("type", __InputTagHelper.Type);
+                __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
+                __tagHelperExecutionContext.Add(__InputTagHelper2);
+                __InputTagHelper2.Type = __InputTagHelper.Type;
+                __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
+                if (__tagHelperExecutionContext.Output.ContentSet)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+                }
+                else if (__tagHelperExecutionContext.ChildContentRetrieved)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+                }
+                else
+                {
+                    __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+                }
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
+                __tagHelperExecutionContext = __tagHelperScopeManager.End();
+                WriteLiteral("\r\n");
 #line 19 "ComplexTagHelpers.cshtml"
             }
 
 #line default
 #line hidden
 
-            Instrumentation.BeginContext(654, 8, true);
-            WriteLiteral("        ");
-            Instrumentation.EndContext();
+                WriteLiteral("        ");
+            }
+            , StartWritingScope, EndWritingScope);
+            __PTagHelper = CreateTagHelper<PTagHelper>();
+            __tagHelperExecutionContext.Add(__PTagHelper);
+            StartWritingScope();
+            WriteLiteral("Current Time: ");
+#line 8 "ComplexTagHelpers.cshtml"
+Write(DateTime.Now);
+
+#line default
+#line hidden
+            __tagHelperStringValueBuffer = EndWritingScope();
+            __tagHelperExecutionContext.AddHtmlAttribute("time", __tagHelperStringValueBuffer.ToString());
+            __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
+            WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
+            WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
+            if (__tagHelperExecutionContext.Output.ContentSet)
+            {
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+            }
+            else if (__tagHelperExecutionContext.ChildContentRetrieved)
+            {
+                WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+            }
+            else
+            {
+                __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+            }
+            WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
             WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
             __tagHelperExecutionContext = __tagHelperScopeManager.End();
-            Instrumentation.BeginContext(666, 14, true);
+            Instrumentation.BeginContext(666, 10, true);
+            WriteLiteral("\r\n        ");
+            Instrumentation.EndContext();
+            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("p", "test", async() => {
+                WriteLiteral("\r\n");
+#line 22 "ComplexTagHelpers.cshtml"
+            
+
+#line default
+#line hidden
+
+#line 22 "ComplexTagHelpers.cshtml"
+               var @object = false;
+
+#line default
+#line hidden
+
+                WriteLiteral("\r\n            ");
+                __tagHelperExecutionContext = __tagHelperScopeManager.Begin("input", "test", async() => {
+                }
+                , StartWritingScope, EndWritingScope);
+                __InputTagHelper = CreateTagHelper<InputTagHelper>();
+                __tagHelperExecutionContext.Add(__InputTagHelper);
+                __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
+                __tagHelperExecutionContext.Add(__InputTagHelper2);
+#line 23 "ComplexTagHelpers.cshtml"
+__InputTagHelper2.Checked = @object;
+
+#line default
+#line hidden
+                __tagHelperExecutionContext.AddTagHelperAttribute("checked", __InputTagHelper2.Checked);
+                __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
+                if (__tagHelperExecutionContext.Output.ContentSet)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+                }
+                else if (__tagHelperExecutionContext.ChildContentRetrieved)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+                }
+                else
+                {
+                    __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+                }
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
+                __tagHelperExecutionContext = __tagHelperScopeManager.End();
+                WriteLiteral("\r\n        ");
+            }
+            , StartWritingScope, EndWritingScope);
+            __PTagHelper = CreateTagHelper<PTagHelper>();
+            __tagHelperExecutionContext.Add(__PTagHelper);
+#line 21 "ComplexTagHelpers.cshtml"
+__PTagHelper.Age = DateTimeOffset.Now.Year - 1970;
+
+#line default
+#line hidden
+            __tagHelperExecutionContext.AddTagHelperAttribute("age", __PTagHelper.Age);
+            __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
+            WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
+            WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
+            if (__tagHelperExecutionContext.Output.ContentSet)
+            {
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+            }
+            else if (__tagHelperExecutionContext.ChildContentRetrieved)
+            {
+                WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+            }
+            else
+            {
+                __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+            }
+            WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
+            WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
+            __tagHelperExecutionContext = __tagHelperScopeManager.End();
+            Instrumentation.BeginContext(813, 10, true);
+            WriteLiteral("\r\n        ");
+            Instrumentation.EndContext();
+            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("p", "test", async() => {
+                WriteLiteral("\r\n            ");
+                __tagHelperExecutionContext = __tagHelperScopeManager.Begin("input", "test", async() => {
+                }
+                , StartWritingScope, EndWritingScope);
+                __InputTagHelper = CreateTagHelper<InputTagHelper>();
+                __tagHelperExecutionContext.Add(__InputTagHelper);
+                __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
+                __tagHelperExecutionContext.Add(__InputTagHelper2);
+#line 26 "ComplexTagHelpers.cshtml"
+__InputTagHelper2.Checked = DateTimeOffset.Now.Year > 2014;
+
+#line default
+#line hidden
+                __tagHelperExecutionContext.AddTagHelperAttribute("checked", __InputTagHelper2.Checked);
+                __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
+                if (__tagHelperExecutionContext.Output.ContentSet)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+                }
+                else if (__tagHelperExecutionContext.ChildContentRetrieved)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+                }
+                else
+                {
+                    __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+                }
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
+                __tagHelperExecutionContext = __tagHelperScopeManager.End();
+                WriteLiteral("\r\n        ");
+            }
+            , StartWritingScope, EndWritingScope);
+            __PTagHelper = CreateTagHelper<PTagHelper>();
+            __tagHelperExecutionContext.Add(__PTagHelper);
+#line 25 "ComplexTagHelpers.cshtml"
+__PTagHelper.Age = -1970 + DateTimeOffset.Now.Year;
+
+#line default
+#line hidden
+            __tagHelperExecutionContext.AddTagHelperAttribute("age", __PTagHelper.Age);
+            __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
+            WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
+            WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
+            if (__tagHelperExecutionContext.Output.ContentSet)
+            {
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+            }
+            else if (__tagHelperExecutionContext.ChildContentRetrieved)
+            {
+                WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+            }
+            else
+            {
+                __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+            }
+            WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
+            WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
+            __tagHelperExecutionContext = __tagHelperScopeManager.End();
+            Instrumentation.BeginContext(946, 10, true);
+            WriteLiteral("\r\n        ");
+            Instrumentation.EndContext();
+            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("p", "test", async() => {
+                WriteLiteral("\r\n            ");
+                __tagHelperExecutionContext = __tagHelperScopeManager.Begin("input", "test", async() => {
+                }
+                , StartWritingScope, EndWritingScope);
+                __InputTagHelper = CreateTagHelper<InputTagHelper>();
+                __tagHelperExecutionContext.Add(__InputTagHelper);
+                __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
+                __tagHelperExecutionContext.Add(__InputTagHelper2);
+#line 29 "ComplexTagHelpers.cshtml"
+__InputTagHelper2.Checked = DateTimeOffset.Now.Year > 2014;
+
+#line default
+#line hidden
+                __tagHelperExecutionContext.AddTagHelperAttribute("checked", __InputTagHelper2.Checked);
+                __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
+                if (__tagHelperExecutionContext.Output.ContentSet)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+                }
+                else if (__tagHelperExecutionContext.ChildContentRetrieved)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+                }
+                else
+                {
+                    __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+                }
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
+                __tagHelperExecutionContext = __tagHelperScopeManager.End();
+                WriteLiteral("\r\n        ");
+            }
+            , StartWritingScope, EndWritingScope);
+            __PTagHelper = CreateTagHelper<PTagHelper>();
+            __tagHelperExecutionContext.Add(__PTagHelper);
+#line 28 "ComplexTagHelpers.cshtml"
+__PTagHelper.Age = DateTimeOffset.Now.Year - 1970;
+
+#line default
+#line hidden
+            __tagHelperExecutionContext.AddTagHelperAttribute("age", __PTagHelper.Age);
+            __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
+            WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
+            WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
+            if (__tagHelperExecutionContext.Output.ContentSet)
+            {
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+            }
+            else if (__tagHelperExecutionContext.ChildContentRetrieved)
+            {
+                WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+            }
+            else
+            {
+                __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+            }
+            WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
+            WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
+            __tagHelperExecutionContext = __tagHelperScopeManager.End();
+            Instrumentation.BeginContext(1074, 10, true);
+            WriteLiteral("\r\n        ");
+            Instrumentation.EndContext();
+            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("p", "test", async() => {
+                WriteLiteral("\r\n            ");
+                __tagHelperExecutionContext = __tagHelperScopeManager.Begin("input", "test", async() => {
+                }
+                , StartWritingScope, EndWritingScope);
+                __InputTagHelper = CreateTagHelper<InputTagHelper>();
+                __tagHelperExecutionContext.Add(__InputTagHelper);
+                __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
+                __tagHelperExecutionContext.Add(__InputTagHelper2);
+#line 32 "ComplexTagHelpers.cshtml"
+__InputTagHelper2.Checked =      DateTimeOffset.Now.Year   > 2014   ;
+
+#line default
+#line hidden
+                __tagHelperExecutionContext.AddTagHelperAttribute("checked", __InputTagHelper2.Checked);
+                __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
+                if (__tagHelperExecutionContext.Output.ContentSet)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+                }
+                else if (__tagHelperExecutionContext.ChildContentRetrieved)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+                }
+                else
+                {
+                    __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+                }
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
+                __tagHelperExecutionContext = __tagHelperScopeManager.End();
+                WriteLiteral("\r\n        ");
+            }
+            , StartWritingScope, EndWritingScope);
+            __PTagHelper = CreateTagHelper<PTagHelper>();
+            __tagHelperExecutionContext.Add(__PTagHelper);
+#line 31 "ComplexTagHelpers.cshtml"
+__PTagHelper.Age = "My age is this long.".Length;
+
+#line default
+#line hidden
+            __tagHelperExecutionContext.AddTagHelperAttribute("age", __PTagHelper.Age);
+            __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
+            WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
+            WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
+            if (__tagHelperExecutionContext.Output.ContentSet)
+            {
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+            }
+            else if (__tagHelperExecutionContext.ChildContentRetrieved)
+            {
+                WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+            }
+            else
+            {
+                __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+            }
+            WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
+            WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
+            __tagHelperExecutionContext = __tagHelperScopeManager.End();
+            Instrumentation.BeginContext(1217, 14, true);
             WriteLiteral("\r\n    </div>\r\n");
             Instrumentation.EndContext();
-#line 22 "ComplexTagHelpers.cshtml"
+#line 35 "ComplexTagHelpers.cshtml"
 }
 
 #line default

test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/CS/Output/ContentBehaviorTagHelpers.DesignTime.cs

@@ -1,45 +0,0 @@
-namespace TestOutput
-{
-    using Microsoft.AspNet.Razor.Runtime.TagHelpers;
-    using System;
-    using System.Threading.Tasks;
-
-    public class ContentBehaviorTagHelpers
-    {
-        private static object @__o;
-        private void @__RazorDesignTimeHelpers__()
-        {
-            #pragma warning disable 219
-            string __tagHelperDirectiveSyntaxHelper = null;
-            __tagHelperDirectiveSyntaxHelper = 
-#line 1 "ContentBehaviorTagHelpers.cshtml"
-              "something"
-
-#line default
-#line hidden
-            ;
-            #pragma warning restore 219
-        }
-        #line hidden
-        private ModifyTagHelper __ModifyTagHelper = null;
-        private NoneTagHelper __NoneTagHelper = null;
-        private AppendTagHelper __AppendTagHelper = null;
-        private PrependTagHelper __PrependTagHelper = null;
-        private ReplaceTagHelper __ReplaceTagHelper = null;
-        #line hidden
-        public ContentBehaviorTagHelpers()
-        {
-        }
-
-        #pragma warning disable 1998
-        public override async Task ExecuteAsync()
-        {
-            __ModifyTagHelper = CreateTagHelper<ModifyTagHelper>();
-            __NoneTagHelper = CreateTagHelper<NoneTagHelper>();
-            __AppendTagHelper = CreateTagHelper<AppendTagHelper>();
-            __PrependTagHelper = CreateTagHelper<PrependTagHelper>();
-            __ReplaceTagHelper = CreateTagHelper<ReplaceTagHelper>();
-        }
-        #pragma warning restore 1998
-    }
-}

test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/CS/Output/ContentBehaviorTagHelpers.cs

@@ -1,83 +0,0 @@
-#pragma checksum "ContentBehaviorTagHelpers.cshtml" "{ff1816ec-aa5e-4d10-87f7-6f4963833460}" "5aeeb0a2b5283b353efaff2cd2fb0c739020b899"
-namespace TestOutput
-{
-    using Microsoft.AspNet.Razor.Runtime.TagHelpers;
-    using System;
-    using System.Threading.Tasks;
-
-    public class ContentBehaviorTagHelpers
-    {
-        #line hidden
-        private System.IO.TextWriter __tagHelperStringValueBuffer = null;
-        private TagHelperExecutionContext __tagHelperExecutionContext = null;
-        private TagHelperRunner __tagHelperRunner = new TagHelperRunner();
-        private TagHelperScopeManager __tagHelperScopeManager = new TagHelperScopeManager();
-        private ModifyTagHelper __ModifyTagHelper = null;
-        private NoneTagHelper __NoneTagHelper = null;
-        private AppendTagHelper __AppendTagHelper = null;
-        private PrependTagHelper __PrependTagHelper = null;
-        private ReplaceTagHelper __ReplaceTagHelper = null;
-        #line hidden
-        public ContentBehaviorTagHelpers()
-        {
-        }
-
-        #pragma warning disable 1998
-        public override async Task ExecuteAsync()
-        {
-            Instrumentation.BeginContext(27, 2, true);
-            WriteLiteral("\r\n");
-            Instrumentation.EndContext();
-            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("modify");
-            __ModifyTagHelper = CreateTagHelper<ModifyTagHelper>();
-            __tagHelperExecutionContext.Add(__ModifyTagHelper);
-            StartWritingScope();
-            WriteLiteral("\r\n    ");
-            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("none");
-            __NoneTagHelper = CreateTagHelper<NoneTagHelper>();
-            __tagHelperExecutionContext.Add(__NoneTagHelper);
-            __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
-            WriteLiteral("\r\n        ");
-            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("append");
-            __AppendTagHelper = CreateTagHelper<AppendTagHelper>();
-            __tagHelperExecutionContext.Add(__AppendTagHelper);
-            __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
-            WriteLiteral("\r\n            ");
-            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("prepend");
-            __PrependTagHelper = CreateTagHelper<PrependTagHelper>();
-            __tagHelperExecutionContext.Add(__PrependTagHelper);
-            __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
-            WriteLiteral("\r\n                ");
-            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("replace");
-            __ReplaceTagHelper = CreateTagHelper<ReplaceTagHelper>();
-            __tagHelperExecutionContext.Add(__ReplaceTagHelper);
-            __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
-            __tagHelperExecutionContext = __tagHelperScopeManager.End();
-            WriteLiteral("\r\n            ");
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
-            __tagHelperExecutionContext = __tagHelperScopeManager.End();
-            WriteLiteral("\r\n        ");
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
-            __tagHelperExecutionContext = __tagHelperScopeManager.End();
-            WriteLiteral("\r\n    ");
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
-            __tagHelperExecutionContext = __tagHelperScopeManager.End();
-            WriteLiteral("\r\n");
-            __tagHelperStringValueBuffer = EndWritingScope();
-            __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext, __tagHelperStringValueBuffer).Result;
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
-            __tagHelperExecutionContext = __tagHelperScopeManager.End();
-        }
-        #pragma warning restore 1998
-    }
-}

test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/CS/Output/SingleTagHelper.DesignTime.cs

@@ -31,7 +31,11 @@ namespace TestOutput
         public override async Task ExecuteAsync()
         {
             __PTagHelper = CreateTagHelper<PTagHelper>();
-            __PTagHelper.Age = 1337;
+#line 3 "SingleTagHelper.cshtml"
+         __PTagHelper.Age = 1337;
+
+#line default
+#line hidden
         }
         #pragma warning restore 1998
     }

test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/CS/Output/SingleTagHelper.cs

@@ -8,7 +8,9 @@ namespace TestOutput
     public class SingleTagHelper
     {
         #line hidden
+        #pragma warning disable 0414
         private System.IO.TextWriter __tagHelperStringValueBuffer = null;
+        #pragma warning restore 0414
         private TagHelperExecutionContext __tagHelperExecutionContext = null;
         private TagHelperRunner __tagHelperRunner = new TagHelperRunner();
         private TagHelperScopeManager __tagHelperScopeManager = new TagHelperScopeManager();
@@ -24,17 +26,35 @@ namespace TestOutput
             Instrumentation.BeginContext(27, 2, true);
             WriteLiteral("\r\n");
             Instrumentation.EndContext();
-            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("p");
+            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("p", "test", async() => {
+                WriteLiteral("Body of Tag");
+            }
+            , StartWritingScope, EndWritingScope);
             __PTagHelper = CreateTagHelper<PTagHelper>();
             __tagHelperExecutionContext.Add(__PTagHelper);
-            __PTagHelper.Age = 1337;
+#line 3 "SingleTagHelper.cshtml"
+         __PTagHelper.Age = 1337;
+
+#line default
+#line hidden
             __tagHelperExecutionContext.AddTagHelperAttribute("age", __PTagHelper.Age);
             __tagHelperExecutionContext.AddHtmlAttribute("class", "Hello World");
             __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
             WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
-            Instrumentation.BeginContext(63, 11, true);
-            WriteLiteral("Body of Tag");
-            Instrumentation.EndContext();
+            WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
+            if (__tagHelperExecutionContext.Output.ContentSet)
+            {
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+            }
+            else if (__tagHelperExecutionContext.ChildContentRetrieved)
+            {
+                WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+            }
+            else
+            {
+                __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+            }
+            WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
             WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
             __tagHelperExecutionContext = __tagHelperScopeManager.End();
         }

test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/CS/Output/TagHelpersInHelper.cs

@@ -24,7 +24,40 @@ MyHelper(string val)
             Instrumentation.BeginContext(62, 19, true);
             WriteLiteralTo(__razor_helper_writer, "    <div>\r\n        ");
             Instrumentation.EndContext();
-            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("mytaghelper");
+            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("mytaghelper", "test", async() => {
+                WriteLiteral("\r\n            In None ContentBehavior.\r\n            ");
+                __tagHelperExecutionContext = __tagHelperScopeManager.Begin("nestedtaghelper", "test", async() => {
+                    WriteLiteral("Some buffered values with a value of ");
+#line 8 "TagHelpersInHelper.cshtml"
+                                            Write(val);
+
+#line default
+#line hidden
+                }
+                , StartWritingScope, EndWritingScope);
+                __NestedTagHelper = CreateTagHelper<NestedTagHelper>();
+                __tagHelperExecutionContext.Add(__NestedTagHelper);
+                __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
+                if (__tagHelperExecutionContext.Output.ContentSet)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+                }
+                else if (__tagHelperExecutionContext.ChildContentRetrieved)
+                {
+                    WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+                }
+                else
+                {
+                    __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+                }
+                WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
+                __tagHelperExecutionContext = __tagHelperScopeManager.End();
+                WriteLiteral("\r\n        ");
+            }
+            , StartWritingScope, EndWritingScope);
             __MyTagHelper = CreateTagHelper<MyTagHelper>();
             __tagHelperExecutionContext.Add(__MyTagHelper);
             StartWritingScope();
@@ -48,28 +81,22 @@ Write(DateTime.Now);
             __tagHelperExecutionContext.AddHtmlAttribute("unboundproperty", __tagHelperStringValueBuffer.ToString());
             __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
             WriteLiteralTo(__razor_helper_writer, __tagHelperExecutionContext.Output.GenerateStartTag());
-            Instrumentation.BeginContext(184, 52, true);
-            WriteLiteralTo(__razor_helper_writer, "\r\n            In None ContentBehavior.\r\n            ");
-            Instrumentation.EndContext();
-            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("nestedtaghelper");
-            __NestedTagHelper = CreateTagHelper<NestedTagHelper>();
-            __tagHelperExecutionContext.Add(__NestedTagHelper);
-            StartWritingScope();
-            WriteLiteral("Some buffered values with a value of ");
-#line 8 "TagHelpersInHelper.cshtml"
-                                            Write(val);
-
-#line default
-#line hidden
-            __tagHelperStringValueBuffer = EndWritingScope();
-            __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext, __tagHelperStringValueBuffer).Result;
-            WriteLiteralTo(__razor_helper_writer, __tagHelperExecutionContext.Output.GenerateStartTag());
-            WriteLiteralTo(__razor_helper_writer, __tagHelperExecutionContext.Output.GenerateContent());
-            WriteLiteralTo(__razor_helper_writer, __tagHelperExecutionContext.Output.GenerateEndTag());
-            __tagHelperExecutionContext = __tagHelperScopeManager.End();
-            Instrumentation.BeginContext(312, 10, true);
-            WriteLiteralTo(__razor_helper_writer, "\r\n        ");
-            Instrumentation.EndContext();
+            WriteLiteralTo(__razor_helper_writer, __tagHelperExecutionContext.Output.GeneratePreContent());
+            if (__tagHelperExecutionContext.Output.ContentSet)
+            {
+                WriteLiteralTo(__razor_helper_writer, __tagHelperExecutionContext.Output.GenerateContent());
+            }
+            else if (__tagHelperExecutionContext.ChildContentRetrieved)
+            {
+                WriteLiteralTo(__razor_helper_writer, __tagHelperExecutionContext.GetChildContentAsync().Result);
+            }
+            else
+            {
+                StartWritingScope(__razor_helper_writer);
+                __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+                EndWritingScope();
+            }
+            WriteLiteralTo(__razor_helper_writer, __tagHelperExecutionContext.Output.GeneratePostContent());
             WriteLiteralTo(__razor_helper_writer, __tagHelperExecutionContext.Output.GenerateEndTag());
             __tagHelperExecutionContext = __tagHelperScopeManager.End();
             Instrumentation.BeginContext(336, 14, true);
@@ -89,7 +116,9 @@ Write(DateTime.Now);
 #line hidden
 
         #line hidden
+        #pragma warning disable 0414
         private System.IO.TextWriter __tagHelperStringValueBuffer = null;
+        #pragma warning restore 0414
         private TagHelperExecutionContext __tagHelperExecutionContext = null;
         private TagHelperRunner __tagHelperRunner = new TagHelperRunner();
         private TagHelperScopeManager __tagHelperScopeManager = new TagHelperScopeManager();
@@ -106,23 +135,33 @@ Write(DateTime.Now);
             Instrumentation.BeginContext(27, 2, true);
             WriteLiteral("\r\n");
             Instrumentation.EndContext();
-            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("mytaghelper");
-            __MyTagHelper = CreateTagHelper<MyTagHelper>();
-            __tagHelperExecutionContext.Add(__MyTagHelper);
-            __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
-            WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
-            Instrumentation.BeginContext(367, 9, false);
+            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("mytaghelper", "test", async() => {
 #line 12 "TagHelpersInHelper.cshtml"
 Write(MyHelper(item => new Template((__razor_template_writer) => {
-    __tagHelperExecutionContext = __tagHelperScopeManager.Begin("nestedtaghelper");
+    __tagHelperExecutionContext = __tagHelperScopeManager.Begin("nestedtaghelper", "test", async() => {
+        WriteLiteral("Custom Value");
+    }
+    , StartWritingScope, EndWritingScope);
     __NestedTagHelper = CreateTagHelper<NestedTagHelper>();
     __tagHelperExecutionContext.Add(__NestedTagHelper);
-    StartWritingScope();
-    WriteLiteral("Custom Value");
-    __tagHelperStringValueBuffer = EndWritingScope();
-    __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext, __tagHelperStringValueBuffer).Result;
+    __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
     WriteLiteralTo(__razor_template_writer, __tagHelperExecutionContext.Output.GenerateStartTag());
-    WriteLiteralTo(__razor_template_writer, __tagHelperExecutionContext.Output.GenerateContent());
+    WriteLiteralTo(__razor_template_writer, __tagHelperExecutionContext.Output.GeneratePreContent());
+    if (__tagHelperExecutionContext.Output.ContentSet)
+    {
+        WriteLiteralTo(__razor_template_writer, __tagHelperExecutionContext.Output.GenerateContent());
+    }
+    else if (__tagHelperExecutionContext.ChildContentRetrieved)
+    {
+        WriteLiteralTo(__razor_template_writer, __tagHelperExecutionContext.GetChildContentAsync().Result);
+    }
+    else
+    {
+        StartWritingScope(__razor_template_writer);
+        __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+        EndWritingScope();
+    }
+    WriteLiteralTo(__razor_template_writer, __tagHelperExecutionContext.Output.GeneratePostContent());
     WriteLiteralTo(__razor_template_writer, __tagHelperExecutionContext.Output.GenerateEndTag());
     __tagHelperExecutionContext = __tagHelperScopeManager.End();
 }
@@ -131,7 +170,26 @@ Write(MyHelper(item => new Template((__razor_template_writer) => {
 
 #line default
 #line hidden
-            Instrumentation.EndContext();
+            }
+            , StartWritingScope, EndWritingScope);
+            __MyTagHelper = CreateTagHelper<MyTagHelper>();
+            __tagHelperExecutionContext.Add(__MyTagHelper);
+            __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
+            WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
+            WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
+            if (__tagHelperExecutionContext.Output.ContentSet)
+            {
+                WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+            }
+            else if (__tagHelperExecutionContext.ChildContentRetrieved)
+            {
+                WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+            }
+            else
+            {
+                __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+            }
+            WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
             WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
             __tagHelperExecutionContext = __tagHelperScopeManager.End();
             Instrumentation.BeginContext(439, 2, true);

test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/CS/Output/TagHelpersInSection.cs

@@ -7,7 +7,9 @@ namespace TestOutput
     public class TagHelpersInSection
     {
         #line hidden
+        #pragma warning disable 0414
         private System.IO.TextWriter __tagHelperStringValueBuffer = null;
+        #pragma warning restore 0414
         private TagHelperExecutionContext __tagHelperExecutionContext = null;
         private TagHelperRunner __tagHelperRunner = new TagHelperRunner();
         private TagHelperScopeManager __tagHelperScopeManager = new TagHelperScopeManager();
@@ -38,7 +40,40 @@ namespace TestOutput
                 Instrumentation.BeginContext(87, 21, true);
                 WriteLiteralTo(__razor_template_writer, "\r\n    <div>\r\n        ");
                 Instrumentation.EndContext();
-                __tagHelperExecutionContext = __tagHelperScopeManager.Begin("mytaghelper");
+                __tagHelperExecutionContext = __tagHelperScopeManager.Begin("mytaghelper", "test", async() => {
+                    WriteLiteral("\r\n            In None ContentBehavior.\r\n            ");
+                    __tagHelperExecutionContext = __tagHelperScopeManager.Begin("nestedtaghelper", "test", async() => {
+                        WriteLiteral("Some buffered values with ");
+#line 11 "TagHelpersInSection.cshtml"
+                                 Write(code);
+
+#line default
+#line hidden
+                    }
+                    , StartWritingScope, EndWritingScope);
+                    __NestedTagHelper = CreateTagHelper<NestedTagHelper>();
+                    __tagHelperExecutionContext.Add(__NestedTagHelper);
+                    __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
+                    WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
+                    WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
+                    if (__tagHelperExecutionContext.Output.ContentSet)
+                    {
+                        WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+                    }
+                    else if (__tagHelperExecutionContext.ChildContentRetrieved)
+                    {
+                        WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+                    }
+                    else
+                    {
+                        __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+                    }
+                    WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
+                    WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
+                    __tagHelperExecutionContext = __tagHelperScopeManager.End();
+                    WriteLiteral("\r\n        ");
+                }
+                , StartWritingScope, EndWritingScope);
                 __MyTagHelper = CreateTagHelper<MyTagHelper>();
                 __tagHelperExecutionContext.Add(__MyTagHelper);
                 StartWritingScope();
@@ -62,28 +97,22 @@ Write(DateTime.Now);
                 __tagHelperExecutionContext.AddHtmlAttribute("unboundproperty", __tagHelperStringValueBuffer.ToString());
                 __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
                 WriteLiteralTo(__razor_template_writer, __tagHelperExecutionContext.Output.GenerateStartTag());
-                Instrumentation.BeginContext(211, 52, true);
-                WriteLiteralTo(__razor_template_writer, "\r\n            In None ContentBehavior.\r\n            ");
-                Instrumentation.EndContext();
-                __tagHelperExecutionContext = __tagHelperScopeManager.Begin("nestedtaghelper");
-                __NestedTagHelper = CreateTagHelper<NestedTagHelper>();
-                __tagHelperExecutionContext.Add(__NestedTagHelper);
-                StartWritingScope();
-                WriteLiteral("Some buffered values with ");
-#line 11 "TagHelpersInSection.cshtml"
-                                 Write(code);
-
-#line default
-#line hidden
-                __tagHelperStringValueBuffer = EndWritingScope();
-                __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext, __tagHelperStringValueBuffer).Result;
-                WriteLiteralTo(__razor_template_writer, __tagHelperExecutionContext.Output.GenerateStartTag());
-                WriteLiteralTo(__razor_template_writer, __tagHelperExecutionContext.Output.GenerateContent());
-                WriteLiteralTo(__razor_template_writer, __tagHelperExecutionContext.Output.GenerateEndTag());
-                __tagHelperExecutionContext = __tagHelperScopeManager.End();
-                Instrumentation.BeginContext(329, 10, true);
-                WriteLiteralTo(__razor_template_writer, "\r\n        ");
-                Instrumentation.EndContext();
+                WriteLiteralTo(__razor_template_writer, __tagHelperExecutionContext.Output.GeneratePreContent());
+                if (__tagHelperExecutionContext.Output.ContentSet)
+                {
+                    WriteLiteralTo(__razor_template_writer, __tagHelperExecutionContext.Output.GenerateContent());
+                }
+                else if (__tagHelperExecutionContext.ChildContentRetrieved)
+                {
+                    WriteLiteralTo(__razor_template_writer, __tagHelperExecutionContext.GetChildContentAsync().Result);
+                }
+                else
+                {
+                    StartWritingScope(__razor_template_writer);
+                    __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
+                    EndWritingScope();
+                }
+                WriteLiteralTo(__razor_template_writer, __tagHelperExecutionContext.Output.GeneratePostContent());
                 WriteLiteralTo(__razor_template_writer, __tagHelperExecutionContext.Output.GenerateEndTag());
                 __tagHelperExecutionContext = __tagHelperScopeManager.End();
                 Instrumentation.BeginContext(353, 14, true);

test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/CS/Source/ComplexTagHelpers.cshtml

@@ -18,5 +18,18 @@
                 <input type='@if(true) { <text>checkbox</text> } else { <text>anything</text> }' />
             }
         </p>
+        <p age="@DateTimeOffset.Now.Year - 1970">
+            @{ var @object = false;}
+            <input checked="@(@object)" />
+        </p>
+        <p age="-1970 + @DateTimeOffset.Now.Year">
+            <input checked="@(DateTimeOffset.Now.Year > 2014)" />
+        </p>
+        <p age="DateTimeOffset.Now.Year - 1970">
+            <input checked="DateTimeOffset.Now.Year > 2014" />
+        </p>
+        <p age="@("My age is this long.".Length)">
+            <input checked="   @(  DateTimeOffset.Now.Year  ) > 2014   " />
+        </p>
     </div>
 }

test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/CS/Source/ContentBehaviorTagHelpers.cshtml

@@ -1,11 +0,0 @@
-@addtaghelper "something"
-
-<modify>
-    <none>
-        <append>
-            <prepend>
-                <replace>This should not be in the output</replace>
-            </prepend>
-        </append>
-    </none>
-</modify>

test/Microsoft.AspNet.Razor.Test/project.json

@@ -5,17 +5,21 @@
         "Moq": "4.2.1312.1622",
         "Microsoft.AspNet.Razor": "4.0.0-*",
         "Microsoft.AspNet.Testing": "1.0.0-*",
-        "Xunit.KRunner": "1.0.0-*"
+        "xunit.runner.kre": "1.0.0-*"
     },
     "commands": {
-        "test": "Xunit.KRunner"
+        "test": "xunit.runner.kre"
     },
     "frameworks": {
         "aspnet50": { },
         "aspnetcore50": {
             "dependencies": {
-                "System.Diagnostics.TraceSource": "4.0.0-beta-*"
+                "System.Diagnostics.TraceSource": "4.0.0-beta-*",
+                "System.Reflection.TypeExtensions": "4.0.0-beta-*"
             }
         }
+    },
+    "compilationOptions": {
+        "define": [ "__RemoveThisBitTo__GENERATE_BASELINES" ]
     }
 }