From 284eb9ac6a4f69f80f2c767a6d35f40dbd091131 Mon Sep 17 00:00:00 2001
From: sornaks <sornaks@microsoft.com>
Date: Mon, 23 Feb 2015 14:35:12 -0800
Subject: [PATCH] Reacting to Razor changes - TagHelperOutput is writing to
 TextWriter instead of string.

---
 .../Rendering/BufferEntryCollection.cs        | 177 ------------------
 .../Rendering/StringCollectionTextWriter.cs   |   3 +-
 src/Microsoft.AspNet.Mvc.Core/project.json    |   1 +
 .../MvcRazorHost.cs                           |   4 +-
 src/Microsoft.AspNet.Mvc.Razor/RazorPage.cs   |  87 ++++++++-
 .../CacheTagHelper.cs                         |   5 +-
 .../FormTagHelper.cs                          |   4 +-
 .../InputTagHelper.cs                         |   6 +-
 .../LabelTagHelper.cs                         |   8 +-
 .../LinkTagHelper.cs                          |  24 +--
 .../OptionTagHelper.cs                        |  13 +-
 .../ScriptTagHelper.cs                        |  31 ++-
 .../SelectTagHelper.cs                        |   2 +-
 .../TextAreaTagHelper.cs                      |   2 +-
 .../ValidationMessageTagHelper.cs             |   8 +-
 .../ValidationSummaryTagHelper.cs             |   3 +-
 .../Rendering/BufferEntryCollectionTest.cs    | 160 ----------------
 .../Runtime/ModelExpressionTagHelper.cs       |  26 +--
 .../RazorPageTest.cs                          | 131 ++++++++++++-
 .../AnchorTagHelperTest.cs                    |  45 +++--
 .../CacheTagHelperTest.cs                     | 173 ++++++++---------
 .../EnvironmentTagHelperTest.cs               |  17 +-
 .../FormTagHelperTest.cs                      |  84 ++++++---
 .../InputTagHelperTest.cs                     | 141 +++++++++-----
 .../Internal/AttributeMatcherTest.cs          |   7 +-
 .../LabelTagHelperTest.cs                     |  48 ++---
 .../LinkTagHelperTest.cs                      |  20 +-
 .../OptionTagHelperTest.cs                    |  39 ++--
 .../ScriptTagHelperTest.cs                    |  25 ++-
 .../SelectTagHelperTest.cs                    |  83 +++++---
 .../TagHelperOutputExtensionsTest.cs          |  14 +-
 .../TextAreaTagHelperTest.cs                  |  26 ++-
 .../ValidationMessageTagHelperTest.cs         |  88 +++++----
 .../ValidationSummaryTagHelperTest.cs         |  89 +++++----
 .../TagHelpers/FooterTagHelper.cs             |   2 +-
 .../TagHelpers/HiddenTagHelper.cs             |   2 +-
 .../TagHelpers/RepeatContentTagHelper.cs      |   4 +-
 .../TagHelpers/TitleTagHelper.cs              |   2 +-
 .../RequestScopedTagHelper.cs                 |   2 +-
 .../TagHelpers/ATagHelper.cs                  |   2 +-
 .../TagHelpers/AutoLinkerTagHelper.cs         |   7 +-
 .../TagHelpers/NestedViewStartTagHelper.cs    |   2 +-
 .../TagHelpers/RootViewStartTagHelper.cs      |   2 +-
 .../TagCloudViewComponentTagHelper.cs         |   3 +-
 .../TagHelpers/WebsiteInformationTagHelper.cs |   4 +-
 45 files changed, 825 insertions(+), 801 deletions(-)
 delete mode 100644 src/Microsoft.AspNet.Mvc.Core/Rendering/BufferEntryCollection.cs
 delete mode 100644 test/Microsoft.AspNet.Mvc.Core.Test/Rendering/BufferEntryCollectionTest.cs

diff --git a/src/Microsoft.AspNet.Mvc.Core/Rendering/BufferEntryCollection.cs b/src/Microsoft.AspNet.Mvc.Core/Rendering/BufferEntryCollection.cs
deleted file mode 100644
index c3c4bae1d5..0000000000
--- a/src/Microsoft.AspNet.Mvc.Core/Rendering/BufferEntryCollection.cs
+++ /dev/null
@@ -1,177 +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 System.Collections;
-using System.Collections.Generic;
-using System.Diagnostics;
-using Microsoft.Framework.Internal;
-
-namespace Microsoft.AspNet.Mvc.Rendering
-{
-    /// <summary>
-    /// Represents a hierarchy of strings and provides an enumerator that iterates over it as a sequence.
-    /// </summary>
-    public class BufferEntryCollection : IEnumerable<string>
-    {
-        // Specifies the maximum size we'll allow for direct conversion from
-        // char arrays to string.
-        private const int MaxCharToStringLength = 1024;
-        private readonly List<object> _buffer = new List<object>();
-
-        public IReadOnlyList<object> BufferEntries
-        {
-            get { return _buffer; }
-        }
-
-        /// <summary>
-        /// Adds a string value to the buffer.
-        /// </summary>
-        /// <param name="value">The value to add.</param>
-        public void Add(string value)
-        {
-            _buffer.Add(value);
-        }
-
-        /// <summary>
-        /// Adds a subarray of characters to the buffer.
-        /// </summary>
-        /// <param name="value">The array to add.</param>
-        /// <param name="index">The character position in the array at which to start copying data.</param>
-        /// <param name="count">The number of characters to copy.</param>
-        public void Add([NotNull] char[] value, int index, int count)
-        {
-            if (index < 0)
-            {
-                throw new ArgumentOutOfRangeException("index");
-            }
-            if (count < 0)
-            {
-                throw new ArgumentOutOfRangeException("count");
-            }
-            if (value.Length - index < count)
-            {
-                throw new ArgumentOutOfRangeException("count");
-            }
-
-            while (count > 0)
-            {
-                // Split large char arrays into 1KB strings.
-                var currentCount = Math.Min(count, MaxCharToStringLength);
-                Add(new string(value, index, currentCount));
-                index += currentCount;
-                count -= currentCount;
-            }
-        }
-
-        /// <summary>
-        /// Adds an instance of <see cref="BufferEntryCollection"/> to the buffer.
-        /// </summary>
-        /// <param name="buffer">The buffer collection to add.</param>
-        public void Add([NotNull] BufferEntryCollection buffer)
-        {
-            _buffer.Add(buffer.BufferEntries);
-        }
-
-        /// <inheritdoc />
-        public IEnumerator<string> GetEnumerator()
-        {
-            return new BufferEntryEnumerator(_buffer);
-        }
-
-        IEnumerator IEnumerable.GetEnumerator()
-        {
-            return GetEnumerator();
-        }
-
-        private sealed class BufferEntryEnumerator : IEnumerator<string>
-        {
-            private readonly Stack<IEnumerator<object>> _enumerators = new Stack<IEnumerator<object>>();
-            private readonly List<object> _initialBuffer;
-
-            public BufferEntryEnumerator(List<object> buffer)
-            {
-                _initialBuffer = buffer;
-                Reset();
-            }
-
-            public IEnumerator<object> CurrentEnumerator
-            {
-                get
-                {
-                    return _enumerators.Peek();
-                }
-            }
-
-            public string Current
-            {
-                get
-                {
-                    var currentEnumerator = CurrentEnumerator;
-                    Debug.Assert(currentEnumerator != null);
-
-                    return (string)currentEnumerator.Current;
-                }
-            }
-
-            object IEnumerator.Current
-            {
-                get
-                {
-                    return Current;
-                }
-            }
-
-            public bool MoveNext()
-            {
-                var currentEnumerator = CurrentEnumerator;
-                if (currentEnumerator.MoveNext())
-                {
-                    var current = currentEnumerator.Current;
-                    var buffer = current as List<object>;
-                    if (buffer != null)
-                    {
-                        // If the next item is a collection, recursively call in to it.
-                        var enumerator = buffer.GetEnumerator();
-                        _enumerators.Push(enumerator);
-                        return MoveNext();
-                    }
-
-                    return true;
-                }
-                else if (_enumerators.Count > 1)
-                {
-                    // The current enumerator is exhausted and we have a parent.
-                    // Pop the current enumerator out and continue with it's parent.
-                    var enumerator = _enumerators.Pop();
-                    enumerator.Dispose();
-
-                    return MoveNext();
-                }
-
-                // We've exactly one element in our stack which cannot move next.
-                return false;
-            }
-
-            public void Reset()
-            {
-                DisposeEnumerators();
-
-                _enumerators.Push(_initialBuffer.GetEnumerator());
-            }
-
-            public void Dispose()
-            {
-                DisposeEnumerators();
-            }
-
-            private void DisposeEnumerators()
-            {
-                while (_enumerators.Count > 0)
-                {
-                    _enumerators.Pop().Dispose();
-                }
-            }
-        }
-    }
-}
\ No newline at end of file
diff --git a/src/Microsoft.AspNet.Mvc.Core/Rendering/StringCollectionTextWriter.cs b/src/Microsoft.AspNet.Mvc.Core/Rendering/StringCollectionTextWriter.cs
index 213dbf6700..264b0ead94 100644
--- a/src/Microsoft.AspNet.Mvc.Core/Rendering/StringCollectionTextWriter.cs
+++ b/src/Microsoft.AspNet.Mvc.Core/Rendering/StringCollectionTextWriter.cs
@@ -40,7 +40,8 @@ namespace Microsoft.AspNet.Mvc.Rendering
         /// <summary>
         /// A collection of entries buffered by this instance of <see cref="StringCollectionTextWriter"/>.
         /// </summary>
-        public BufferEntryCollection Buffer { get; private set; }
+        // internal for testing purposes.
+        internal BufferEntryCollection Buffer { get; }
 
         /// <inheritdoc />
         public override void Write(char value)
diff --git a/src/Microsoft.AspNet.Mvc.Core/project.json b/src/Microsoft.AspNet.Mvc.Core/project.json
index afa53fc9c4..db7eb1d073 100644
--- a/src/Microsoft.AspNet.Mvc.Core/project.json
+++ b/src/Microsoft.AspNet.Mvc.Core/project.json
@@ -15,6 +15,7 @@
     "Microsoft.AspNet.Mvc.Common": { "version": "6.0.0-*", "type": "build" },
     "Microsoft.AspNet.Mvc.ModelBinding": "6.0.0-*",
     "Microsoft.AspNet.Routing": "1.0.0-*",
+    "Microsoft.Framework.BufferEntryCollection.Internal": { "version": "1.0.0-*", "type": "build" },
     "Microsoft.Framework.CopyOnWriteDictionary.Internal": { "version": "1.0.0-*", "type": "build" },
     "Microsoft.Framework.NotNullAttribute.Internal": { "version": "1.0.0-*", "type": "build" },
     "Microsoft.Framework.PropertyActivator.Internal": { "version": "1.0.0-*", "type": "build" },
diff --git a/src/Microsoft.AspNet.Mvc.Razor.Host/MvcRazorHost.cs b/src/Microsoft.AspNet.Mvc.Razor.Host/MvcRazorHost.cs
index a639c4cf62..24472fe115 100644
--- a/src/Microsoft.AspNet.Mvc.Razor.Host/MvcRazorHost.cs
+++ b/src/Microsoft.AspNet.Mvc.Razor.Host/MvcRazorHost.cs
@@ -98,8 +98,8 @@ namespace Microsoft.AspNet.Mvc.Razor
 
                     // Can't use nameof because RazorPage is not accessible here.
                     CreateTagHelperMethodName = "CreateTagHelper",
-                    StartWritingScopeMethodName = "StartWritingScope",
-                    EndWritingScopeMethodName = "EndWritingScope",
+                    StartTagHelperWritingScopeMethodName = "StartTagHelperWritingScope",
+                    EndTagHelperWritingScopeMethodName = "EndTagHelperWritingScope",
                     HtmlEncoderPropertyName = "HtmlEncoder",
                 })
             {
diff --git a/src/Microsoft.AspNet.Mvc.Razor/RazorPage.cs b/src/Microsoft.AspNet.Mvc.Razor/RazorPage.cs
index 7939e032c4..4f48356ce2 100644
--- a/src/Microsoft.AspNet.Mvc.Razor/RazorPage.cs
+++ b/src/Microsoft.AspNet.Mvc.Razor/RazorPage.cs
@@ -6,6 +6,7 @@ using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using System.Security.Principal;
+using System.Text;
 using System.Threading.Tasks;
 using Microsoft.AspNet.Http;
 using Microsoft.AspNet.Mvc.Rendering;
@@ -159,11 +160,11 @@ namespace Microsoft.AspNet.Mvc.Razor
         /// </summary>
         /// <remarks>
         /// All writes to the <see cref="Output"/> or <see cref="ViewContext.Writer"/> after calling this method will
-        /// be buffered until <see cref="EndWritingScope"/> is called.
+        /// be buffered until <see cref="EndTagHelperWritingScope"/> is called.
         /// </remarks>
-        public void StartWritingScope()
+        public void StartTagHelperWritingScope()
         {
-            StartWritingScope(new StringWriter());
+            StartTagHelperWritingScope(new StringCollectionTextWriter(Output.Encoding));
         }
 
         /// <summary>
@@ -171,9 +172,9 @@ namespace Microsoft.AspNet.Mvc.Razor
         /// </summary>
         /// <remarks>
         /// All writes to the <see cref="Output"/> or <see cref="ViewContext.Writer"/> after calling this method will
-        /// be buffered until <see cref="EndWritingScope"/> is called.
+        /// be buffered until <see cref="EndTagHelperWritingScope"/> is called.
         /// </remarks>
-        public void StartWritingScope(TextWriter writer)
+        public void StartTagHelperWritingScope(TextWriter writer)
         {
             // If there isn't a base writer take the ViewContext.Writer
             if (_originalWriter == null)
@@ -189,11 +190,11 @@ namespace Microsoft.AspNet.Mvc.Razor
         }
 
         /// <summary>
-        /// Ends the current writing scope that was started by calling <see cref="StartWritingScope"/>.
+        /// Ends the current writing scope that was started by calling <see cref="StartTagHelperWritingScope"/>.
         /// </summary>
         /// <returns>The <see cref="TextWriter"/> that contains the content written to the <see cref="Output"/> or
         /// <see cref="ViewContext.Writer"/> during the writing scope.</returns>
-        public TextWriter EndWritingScope()
+        public TagHelperContent EndTagHelperWritingScope()
         {
             if (_writerScopes.Count == 0)
             {
@@ -214,7 +215,49 @@ namespace Microsoft.AspNet.Mvc.Razor
                 _originalWriter = null;
             }
 
-            return writer;
+            var tagHelperContentWrapperTextWriter = new TagHelperContentWrapperTextWriter(Output.Encoding);
+            var razorWriter = writer as RazorTextWriter;
+            if (razorWriter != null)
+            {
+                razorWriter.CopyTo(tagHelperContentWrapperTextWriter);
+            }
+            else
+            {
+                var stringCollectionTextWriter = writer as StringCollectionTextWriter;
+                if (stringCollectionTextWriter != null)
+                {
+                    stringCollectionTextWriter.CopyTo(tagHelperContentWrapperTextWriter);
+                }
+                else
+                {
+                    tagHelperContentWrapperTextWriter.Write(writer.ToString());
+                }
+            }
+
+            return tagHelperContentWrapperTextWriter.Content;
+        }
+
+        /// <summary>
+        /// Writes an <see cref="ITextWriterCopyable"/> to the <see cref="Output"/>.
+        /// </summary>
+        /// <param name="copyableTextWriter">Contains the data to be written.</param>
+        public void Write(ITextWriterCopyable copyableTextWriter)
+        {
+            WriteTo(Output, copyableTextWriter);
+        }
+
+        /// <summary>
+        /// Writes an <see cref="ITextWriterCopyable"/> to the <paramref name="writer"/>.
+        /// </summary>
+        /// <param name="writer">The <see cref="TextWriter"/> to which the
+        /// <paramref name="copyableTextWriter"/> is written.</param>
+        /// <param name="copyableTextWriter">Contains the data to be written.</param>
+        public void WriteTo(TextWriter writer, ITextWriterCopyable copyableTextWriter)
+        {
+            if (copyableTextWriter != null)
+            {
+                copyableTextWriter.CopyTo(writer);
+            }
         }
 
         /// <summary>
@@ -649,5 +692,33 @@ namespace Microsoft.AspNet.Mvc.Razor
                 throw new InvalidOperationException(Resources.FormatRazorPage_MethodCannotBeCalled(methodName));
             }
         }
+
+        private class TagHelperContentWrapperTextWriter : TextWriter
+        {
+            public TagHelperContentWrapperTextWriter(Encoding encoding)
+            {
+                Content = new DefaultTagHelperContent();
+                Encoding = encoding;
+            }
+
+            public TagHelperContent Content { get; }
+
+            public override Encoding Encoding { get; }
+
+            public override void Write(string value)
+            {
+                Content.Append(value);
+            }
+
+            public override void Write(char value)
+            {
+                Content.Append(value.ToString());
+            }
+
+            public override string ToString()
+            {
+                return Content.ToString();
+            }
+        }
     }
 }
\ No newline at end of file
diff --git a/src/Microsoft.AspNet.Mvc.TagHelpers/CacheTagHelper.cs b/src/Microsoft.AspNet.Mvc.TagHelpers/CacheTagHelper.cs
index c177c9fa99..27e61389e7 100644
--- a/src/Microsoft.AspNet.Mvc.TagHelpers/CacheTagHelper.cs
+++ b/src/Microsoft.AspNet.Mvc.TagHelpers/CacheTagHelper.cs
@@ -112,7 +112,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         public override async Task ProcessAsync(TagHelperContext context, TagHelperOutput output)
         {
             var key = GenerateKey(context);
-            string result;
+            TagHelperContent result;
             if (!MemoryCache.TryGetValue(key, out result))
             {
                 // Create an EntryLink and flow it so that it is accessible via the ambient EntryLinkHelpers.ContentLink
@@ -132,8 +132,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
 
             // Clear the contents of the "cache" element since we don't want to render it.
             output.SuppressOutput();
-
-            output.Content = result;
+            output.Content.SetContent(result);
         }
 
         // Internal for unit testing
diff --git a/src/Microsoft.AspNet.Mvc.TagHelpers/FormTagHelper.cs b/src/Microsoft.AspNet.Mvc.TagHelpers/FormTagHelper.cs
index fe92d7f47f..7584d2b295 100644
--- a/src/Microsoft.AspNet.Mvc.TagHelpers/FormTagHelper.cs
+++ b/src/Microsoft.AspNet.Mvc.TagHelpers/FormTagHelper.cs
@@ -104,7 +104,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 if (tagBuilder != null)
                 {
                     output.MergeAttributes(tagBuilder);
-                    output.PostContent += tagBuilder.InnerHtml;
+                    output.PostContent.Append(tagBuilder.InnerHtml);
                 }
             }
 
@@ -113,7 +113,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 var antiForgeryTagBuilder = Generator.GenerateAntiForgery(ViewContext);
                 if (antiForgeryTagBuilder != null)
                 {
-                    output.PostContent += antiForgeryTagBuilder.ToString(TagRenderMode.SelfClosing);
+                    output.PostContent.Append(antiForgeryTagBuilder.ToString(TagRenderMode.SelfClosing));
                 }
             }
         }
diff --git a/src/Microsoft.AspNet.Mvc.TagHelpers/InputTagHelper.cs b/src/Microsoft.AspNet.Mvc.TagHelpers/InputTagHelper.cs
index 9410f36fff..49bda15739 100644
--- a/src/Microsoft.AspNet.Mvc.TagHelpers/InputTagHelper.cs
+++ b/src/Microsoft.AspNet.Mvc.TagHelpers/InputTagHelper.cs
@@ -206,7 +206,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                     // This TagBuilder contains the one <input/> element of interest. Since this is not the "checkbox"
                     // special-case, output is a self-closing element no longer guarunteed.
                     output.MergeAttributes(tagBuilder);
-                    output.Content += tagBuilder.InnerHtml;
+                    output.Content.Append(tagBuilder.InnerHtml);
                 }
             }
         }
@@ -242,12 +242,12 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 output.Attributes.Clear();
                 output.TagName = null;
 
-                output.Content += tagBuilder.ToString(TagRenderMode.SelfClosing);
+                output.Content.Append(tagBuilder.ToString(TagRenderMode.SelfClosing));
 
                 tagBuilder = Generator.GenerateHiddenForCheckbox(ViewContext, modelExplorer, For.Name);
                 if (tagBuilder != null)
                 {
-                    output.Content += tagBuilder.ToString(TagRenderMode.SelfClosing);
+                    output.Content.Append(tagBuilder.ToString(TagRenderMode.SelfClosing));
                 }
             }
         }
diff --git a/src/Microsoft.AspNet.Mvc.TagHelpers/LabelTagHelper.cs b/src/Microsoft.AspNet.Mvc.TagHelpers/LabelTagHelper.cs
index 9cdebd145e..e691c018b0 100644
--- a/src/Microsoft.AspNet.Mvc.TagHelpers/LabelTagHelper.cs
+++ b/src/Microsoft.AspNet.Mvc.TagHelpers/LabelTagHelper.cs
@@ -47,18 +47,18 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                     // We check for whitespace to detect scenarios such as:
                     // <label for="Name">
                     // </label>
-                    if (!output.ContentSet)
+                    if (!output.IsContentModified)
                     {
                         var childContent = await context.GetChildContentAsync();
 
-                        if (string.IsNullOrWhiteSpace(childContent))
+                        if (childContent.IsWhiteSpace)
                         {
                             // Provide default label text since there was nothing useful in the Razor source.
-                            output.Content = tagBuilder.InnerHtml;
+                            output.Content.SetContent(tagBuilder.InnerHtml);
                         }
                         else
                         {
-                            output.Content = childContent;
+                            output.Content.SetContent(childContent);
                         }
                     }
                 }
diff --git a/src/Microsoft.AspNet.Mvc.TagHelpers/LinkTagHelper.cs b/src/Microsoft.AspNet.Mvc.TagHelpers/LinkTagHelper.cs
index 543e863d90..134db5b895 100644
--- a/src/Microsoft.AspNet.Mvc.TagHelpers/LinkTagHelper.cs
+++ b/src/Microsoft.AspNet.Mvc.TagHelpers/LinkTagHelper.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.Globalization;
 using System.Linq;
@@ -175,7 +176,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             // NOTE: Values in TagHelperOutput.Attributes are already HtmlEncoded
             var attributes = new Dictionary<string, string>(output.Attributes);
 
-            var builder = new StringBuilder();
+            var builder = new DefaultTagHelperContent();
 
             if (mode == Mode.Fallback && string.IsNullOrEmpty(HrefInclude))
             {
@@ -194,10 +195,10 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
 
             // We've taken over tag rendering, so prevent rendering the outer tag
             output.TagName = null;
-            output.Content = builder.ToString();
+            output.Content.SetContent(builder);
         }
 
-        private void BuildGlobbedLinkTags(IDictionary<string, string> attributes, StringBuilder builder)
+        private void BuildGlobbedLinkTags(IDictionary<string, string> attributes, TagHelperContent builder)
         {
             // Build a <link /> tag for each matched href as well as the original one in the source file
             string staticHref;
@@ -213,30 +214,30 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             }
         }
 
-        private void BuildFallbackBlock(StringBuilder builder)
+        private void BuildFallbackBlock(TagHelperContent builder)
         {
             EnsureGlobbingUrlBuilder();
             var fallbackHrefs = GlobbingUrlBuilder.BuildUrlList(FallbackHref, FallbackHrefInclude, FallbackHrefExclude);
 
             if (fallbackHrefs.Any())
             {
-                builder.AppendLine();
+                builder.Append(Environment.NewLine);
 
                 // Build the <meta /> tag that's used to test for the presence of the stylesheet
-                builder.AppendFormat(
+                builder.Append(string.Format(
                     CultureInfo.InvariantCulture,
                     "<meta name=\"x-stylesheet-fallback-test\" class=\"{0}\" />",
-                    HtmlEncoder.HtmlEncode(FallbackTestClass));
+                    HtmlEncoder.HtmlEncode(FallbackTestClass)));
                 
                 // Build the <script /> tag that checks the effective style of <meta /> tag above and renders the extra
                 // <link /> tag to load the fallback stylesheet if the test CSS property value is found to be false,
                 // indicating that the primary stylesheet failed to load.
                 builder.Append("<script>")
-                       .AppendFormat(CultureInfo.InvariantCulture,
+                       .Append(string.Format(CultureInfo.InvariantCulture,
                             JavaScriptResources.GetEmbeddedJavaScript(FallbackJavaScriptResourceName),
                             JavaScriptStringEncoder.Default.JavaScriptStringEncode(FallbackTestProperty),
                             JavaScriptStringEncoder.Default.JavaScriptStringEncode(FallbackTestValue),
-                            JavaScriptStringArrayEncoder.Encode(JavaScriptStringEncoder.Default, fallbackHrefs))
+                            JavaScriptStringArrayEncoder.Encode(JavaScriptStringEncoder.Default, fallbackHrefs)))
                        .Append("</script>");
             }
         }
@@ -252,13 +253,14 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             }
         }
 
-        private static void BuildLinkTag(IDictionary<string, string> attributes, StringBuilder builder)
+        private static void BuildLinkTag(IDictionary<string, string> attributes, TagHelperContent builder)
         {
             builder.Append("<link ");
 
             foreach (var attribute in attributes)
             {
-                builder.AppendFormat(CultureInfo.InvariantCulture, "{0}=\"{1}\" ", attribute.Key, attribute.Value);
+                builder.Append(
+                    string.Format(CultureInfo.InvariantCulture, "{0}=\"{1}\" ", attribute.Key, attribute.Value));
             }
 
             builder.Append("/>");
diff --git a/src/Microsoft.AspNet.Mvc.TagHelpers/OptionTagHelper.cs b/src/Microsoft.AspNet.Mvc.TagHelpers/OptionTagHelper.cs
index 507e0ac597..aca4a87b85 100644
--- a/src/Microsoft.AspNet.Mvc.TagHelpers/OptionTagHelper.cs
+++ b/src/Microsoft.AspNet.Mvc.TagHelpers/OptionTagHelper.cs
@@ -86,8 +86,17 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                     // Select this <option/> element if value attribute or content matches a selected value. Callers
                     // encode values as-needed while executing child content. But TagHelperOutput itself
                     // encodes attribute values later, when GenerateStartTag() is called.
-                    var text = await context.GetChildContentAsync();
-                    var selected = (Value != null) ? selectedValues.Contains(Value) : encodedValues.Contains(text);
+                    bool selected;
+                    if (Value != null)
+                    {
+                        selected = selectedValues.Contains(Value);
+                    }
+                    else
+                    {
+                        var childContent = await context.GetChildContentAsync();
+                        selected = encodedValues.Contains(childContent.GetContent());
+                    }
+
                     if (selected)
                     {
                         output.Attributes.Add("selected", "selected");
diff --git a/src/Microsoft.AspNet.Mvc.TagHelpers/ScriptTagHelper.cs b/src/Microsoft.AspNet.Mvc.TagHelpers/ScriptTagHelper.cs
index bbcaa8b466..2d68008fee 100644
--- a/src/Microsoft.AspNet.Mvc.TagHelpers/ScriptTagHelper.cs
+++ b/src/Microsoft.AspNet.Mvc.TagHelpers/ScriptTagHelper.cs
@@ -5,7 +5,6 @@ using System;
 using System.Collections.Generic;
 using System.Globalization;
 using System.Linq;
-using System.Text;
 using System.Threading.Tasks;
 using Microsoft.AspNet.Hosting;
 using Microsoft.AspNet.Mvc.TagHelpers.Internal;
@@ -155,7 +154,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             // NOTE: Values in TagHelperOutput.Attributes are already HtmlEncoded
             var attributes = new Dictionary<string, string>(output.Attributes);
             
-            var builder = new StringBuilder();
+            var builder = new DefaultTagHelperContent();
             var originalContent = await context.GetChildContentAsync();
 
             if (mode == Mode.Fallback && string.IsNullOrEmpty(SrcInclude))
@@ -175,13 +174,13 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
 
             // We've taken over tag rendering, so prevent rendering the outer tag
             output.TagName = null;
-            output.Content = builder.ToString();
+            output.Content.SetContent(builder);
         }
 
         private void BuildGlobbedScriptTags(
-            string originalContent,
+            TagHelperContent originalContent,
             IDictionary<string, string> attributes,
-            StringBuilder builder)
+            TagHelperContent builder)
         {
             // Build a <script> tag for each matched src as well as the original one in the source file
             string staticSrc;
@@ -193,14 +192,13 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             foreach (var url in urls)
             {
                 attributes["src"] = HtmlEncoder.HtmlEncode(url);
-                var content = string.Equals(url, staticSrc, StringComparison.OrdinalIgnoreCase)
-                    ? originalContent
-                    : string.Empty;
+                var content =
+                    string.Equals(url, staticSrc, StringComparison.OrdinalIgnoreCase) ? originalContent : null;
                 BuildScriptTag(content, attributes, builder);
             }
         }
 
-        private void BuildFallbackBlock(IDictionary<string, string> attributes, StringBuilder builder)
+        private void BuildFallbackBlock(IDictionary<string, string> attributes, DefaultTagHelperContent builder)
         {
             EnsureGlobbingUrlBuilder();
 
@@ -209,7 +207,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             if (fallbackSrcs.Any())
             {
                 // Build the <script> tag that checks the test method and if it fails, renders the extra script.
-                builder.AppendLine()
+                builder.Append(Environment.NewLine)
                        .Append("<script>(")
                        .Append(FallbackTestExpression)
                        .Append("||document.write(\"");
@@ -230,11 +228,11 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                             var encodedKey = JavaScriptStringEncoder.Default.JavaScriptStringEncode(attribute.Key);
                             var encodedValue = JavaScriptStringEncoder.Default.JavaScriptStringEncode(attribute.Value);
 
-                            builder.AppendFormat(
+                            builder.Append(string.Format(
                                 CultureInfo.InvariantCulture,
                                 " {0}=\\\"{1}\\\"",
                                 encodedKey,
-                                encodedValue);
+                                encodedValue));
                         }
                         else
                         {
@@ -261,15 +259,16 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         }
 
         private static void BuildScriptTag(
-            string content,
+            TagHelperContent content,
             IDictionary<string, string> attributes,
-            StringBuilder builder)
+            TagHelperContent builder)
         {
             builder.Append("<script");
 
             foreach (var attribute in attributes)
             {
-                builder.AppendFormat(CultureInfo.InvariantCulture, " {0}=\"{1}\"", attribute.Key, attribute.Value);
+                builder.Append(
+                    string.Format(CultureInfo.InvariantCulture, " {0}=\"{1}\"", attribute.Key, attribute.Value));
             }
 
             builder.Append(">")
@@ -277,7 +276,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                    .Append("</script>");
         }
 
-        private void AppendSrc(StringBuilder content, string srcKey, string srcValue)
+        private void AppendSrc(TagHelperContent content, string srcKey, string srcValue)
         {
             // Append src attribute in the original place and replace the content the fallback content
             // No need to encode the key because we know it is "src".
diff --git a/src/Microsoft.AspNet.Mvc.TagHelpers/SelectTagHelper.cs b/src/Microsoft.AspNet.Mvc.TagHelpers/SelectTagHelper.cs
index e6a3b7c54d..3b51d0aade 100644
--- a/src/Microsoft.AspNet.Mvc.TagHelpers/SelectTagHelper.cs
+++ b/src/Microsoft.AspNet.Mvc.TagHelpers/SelectTagHelper.cs
@@ -107,7 +107,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 if (tagBuilder != null)
                 {
                     output.MergeAttributes(tagBuilder);
-                    output.PostContent += tagBuilder.InnerHtml;
+                    output.PostContent.Append(tagBuilder.InnerHtml);
                 }
 
                 // Whether or not (not being highly unlikely) we generate anything, could update contained <option/>
diff --git a/src/Microsoft.AspNet.Mvc.TagHelpers/TextAreaTagHelper.cs b/src/Microsoft.AspNet.Mvc.TagHelpers/TextAreaTagHelper.cs
index 23323b7d47..9da0f1d002 100644
--- a/src/Microsoft.AspNet.Mvc.TagHelpers/TextAreaTagHelper.cs
+++ b/src/Microsoft.AspNet.Mvc.TagHelpers/TextAreaTagHelper.cs
@@ -46,7 +46,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 if (tagBuilder != null)
                 {
                     // Overwrite current Content to ensure expression result round-trips correctly.
-                    output.Content = tagBuilder.InnerHtml;
+                    output.Content.SetContent(tagBuilder.InnerHtml);
 
                     output.MergeAttributes(tagBuilder);
                 }
diff --git a/src/Microsoft.AspNet.Mvc.TagHelpers/ValidationMessageTagHelper.cs b/src/Microsoft.AspNet.Mvc.TagHelpers/ValidationMessageTagHelper.cs
index 4c59ab0e80..6e22808c0f 100644
--- a/src/Microsoft.AspNet.Mvc.TagHelpers/ValidationMessageTagHelper.cs
+++ b/src/Microsoft.AspNet.Mvc.TagHelpers/ValidationMessageTagHelper.cs
@@ -49,18 +49,18 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                     // We check for whitespace to detect scenarios such as:
                     // <span validation-for="Name">
                     // </span>
-                    if (!output.ContentSet)
+                    if (!output.IsContentModified)
                     {
                         var childContent = await context.GetChildContentAsync();
 
-                        if (string.IsNullOrWhiteSpace(childContent))
+                        if (childContent.IsWhiteSpace)
                         {
                             // Provide default label text since there was nothing useful in the Razor source.
-                            output.Content = tagBuilder.InnerHtml;
+                            output.Content.SetContent(tagBuilder.InnerHtml);
                         }
                         else
                         {
-                            output.Content = childContent;
+                            output.Content.SetContent(childContent);
                         }
                     }
                 }
diff --git a/src/Microsoft.AspNet.Mvc.TagHelpers/ValidationSummaryTagHelper.cs b/src/Microsoft.AspNet.Mvc.TagHelpers/ValidationSummaryTagHelper.cs
index 5ef65fd5ac..95441192aa 100644
--- a/src/Microsoft.AspNet.Mvc.TagHelpers/ValidationSummaryTagHelper.cs
+++ b/src/Microsoft.AspNet.Mvc.TagHelpers/ValidationSummaryTagHelper.cs
@@ -4,7 +4,6 @@
 using System;
 using Microsoft.AspNet.Mvc.Rendering;
 using Microsoft.AspNet.Razor.Runtime.TagHelpers;
-using Microsoft.AspNet.Razor.TagHelpers;
 
 namespace Microsoft.AspNet.Mvc.TagHelpers
 {
@@ -80,7 +79,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             if (tagBuilder != null)
             {
                 output.MergeAttributes(tagBuilder);
-                output.PostContent += tagBuilder.InnerHtml;
+                output.PostContent.Append(tagBuilder.InnerHtml);
             }
         }
     }
diff --git a/test/Microsoft.AspNet.Mvc.Core.Test/Rendering/BufferEntryCollectionTest.cs b/test/Microsoft.AspNet.Mvc.Core.Test/Rendering/BufferEntryCollectionTest.cs
deleted file mode 100644
index 251634f016..0000000000
--- a/test/Microsoft.AspNet.Mvc.Core.Test/Rendering/BufferEntryCollectionTest.cs
+++ /dev/null
@@ -1,160 +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 System.Collections.Generic;
-using System.Linq;
-using Xunit;
-
-namespace Microsoft.AspNet.Mvc.Rendering
-{
-    public class BufferEntryCollectionTest
-    {
-        [Fact]
-        public void Add_AddsBufferEntries()
-        {
-            // Arrange
-            var collection = new BufferEntryCollection();
-            var inner = new BufferEntryCollection();
-
-            // Act
-            collection.Add("Hello");
-            collection.Add(new[] { 'a', 'b', 'c' }, 1, 2);
-            collection.Add(inner);
-
-            // Assert
-            Assert.Equal("Hello", collection.BufferEntries[0]);
-            Assert.Equal("bc", collection.BufferEntries[1]);
-            Assert.Same(inner.BufferEntries, collection.BufferEntries[2]);
-        }
-
-        [Fact]
-        public void AddChar_ThrowsIfIndexIsOutOfBounds()
-        {
-            // Arrange
-            var collection = new BufferEntryCollection();
-
-            // Act and Assert
-            var ex = Assert.Throws<ArgumentOutOfRangeException>(
-                () => collection.Add(new[] { 'a', 'b', 'c' }, -1, 2));
-            Assert.Equal("index", ex.ParamName);
-        }
-
-        [Fact]
-        public void AddChar_ThrowsIfCountWouldCauseOutOfBoundReads()
-        {
-            // Arrange
-            var collection = new BufferEntryCollection();
-
-            // Act and Assert
-            var ex = Assert.Throws<ArgumentOutOfRangeException>(
-                () => collection.Add(new[] { 'a', 'b', 'c' }, 1, 3));
-            Assert.Equal("count", ex.ParamName);
-        }
-
-        public static IEnumerable<object[]> AddWithChar_RepresentsStringsAsChunkedEntriesData
-        {
-            get
-            {
-                var charArray1 = new[] { 'a' };
-                var expected1 = new[] { "a" };
-                yield return new object[] { charArray1, 0, 1, expected1 };
-
-                var charArray2 = Enumerable.Repeat('a', 10).ToArray();
-                var expected2 = new[] { new string(charArray2) };
-                yield return new object[] { charArray2, 0, 10, expected2 };
-
-                var charArray3 = Enumerable.Repeat('b', 1024).ToArray();
-                var expected3 = new[] { new string('b', 1023) };
-                yield return new object[] { charArray3, 1, 1023, expected3 };
-
-                var charArray4 = Enumerable.Repeat('c', 1027).ToArray();
-                var expected4 = new[] { new string('c', 1024), "cc" };
-                yield return new object[] { charArray4, 1, 1026, expected4 };
-
-                var charArray5 = Enumerable.Repeat('d', 4099).ToArray();
-                var expected5 = new[] { new string('d', 1024), new string('d', 1024), new string('d', 1024), new string('d', 1024), "d" };
-                yield return new object[] { charArray5, 2, 4097, expected5 };
-
-                var charArray6 = Enumerable.Repeat('e', 1025).ToArray();
-                var expected6 = new[] { "ee" };
-                yield return new object[] { charArray6, 1023, 2, expected6 };
-            }
-        }
-
-        [Theory]
-        [MemberData(nameof(AddWithChar_RepresentsStringsAsChunkedEntriesData))]
-        public void AddWithChar_RepresentsStringsAsChunkedEntries(char[] value, int index, int count, IList<object> expected)
-        {
-            // Arrange
-            var collection = new BufferEntryCollection();
-
-            // Act
-            collection.Add(value, index, count);
-
-            // Assert
-            Assert.Equal(expected, collection.BufferEntries);
-        }
-
-        public static IEnumerable<object[]> Enumerator_TraversesThroughBufferData
-        {
-            get
-            {
-                var collection1 = new BufferEntryCollection();
-                collection1.Add("foo");
-                collection1.Add("bar");
-
-                var expected1 = new[]
-                {
-                    "foo",
-                    "bar"
-                };
-                yield return new object[] { collection1, expected1 };
-
-                // Nested collection
-                var nestedCollection2 = new BufferEntryCollection();
-                nestedCollection2.Add("level 1");
-                var nestedCollection2SecondLevel = new BufferEntryCollection();
-                nestedCollection2SecondLevel.Add("level 2");
-                nestedCollection2.Add(nestedCollection2SecondLevel);
-                var collection2 = new BufferEntryCollection();
-                collection2.Add("foo");
-                collection2.Add(nestedCollection2);
-                collection2.Add("qux");
-
-                var expected2 = new[]
-                {
-                    "foo",
-                    "level 1",
-                    "level 2",
-                    "qux"
-                };
-                yield return new object[] { collection2, expected2 };
-
-                // Nested collection
-                var collection3 = new BufferEntryCollection();
-                collection3.Add("Hello");
-                var emptyNestedCollection = new BufferEntryCollection();
-                emptyNestedCollection.Add(new BufferEntryCollection());
-                collection3.Add(emptyNestedCollection);
-                collection3.Add("world");
-
-                var expected3 = new[]
-                {
-                    "Hello",
-                    "world"
-                };
-                yield return new object[] { collection3, expected3 };
-            }
-        }
-
-
-        [Theory]
-        [MemberData(nameof(Enumerator_TraversesThroughBufferData))]
-        public void Enumerator_TraversesThroughBuffer(BufferEntryCollection buffer, string[] expected)
-        {
-            // Act and Assert
-            Assert.Equal(expected, buffer);
-        }
-    }
-}
\ No newline at end of file
diff --git a/test/Microsoft.AspNet.Mvc.Razor.Host.Test/TestFiles/Output/Runtime/ModelExpressionTagHelper.cs b/test/Microsoft.AspNet.Mvc.Razor.Host.Test/TestFiles/Output/Runtime/ModelExpressionTagHelper.cs
index 4de90e5cda..70b6e4c8e1 100644
--- a/test/Microsoft.AspNet.Mvc.Razor.Host.Test/TestFiles/Output/Runtime/ModelExpressionTagHelper.cs
+++ b/test/Microsoft.AspNet.Mvc.Razor.Host.Test/TestFiles/Output/Runtime/ModelExpressionTagHelper.cs
@@ -19,7 +19,7 @@ namespace Asp
     {
         #line hidden
         #pragma warning disable 0414
-        private System.IO.TextWriter __tagHelperStringValueBuffer = null;
+        private TagHelperContent __tagHelperStringValueBuffer = null;
         #pragma warning restore 0414
         private Microsoft.AspNet.Razor.Runtime.TagHelpers.TagHelperExecutionContext __tagHelperExecutionContext = null;
         private Microsoft.AspNet.Razor.Runtime.TagHelpers.TagHelperRunner __tagHelperRunner = null;
@@ -48,7 +48,7 @@ namespace Asp
             EndContext();
             __tagHelperExecutionContext = __tagHelperScopeManager.Begin("input-test", true, "test", async() => {
             }
-            , StartWritingScope, EndWritingScope);
+            , StartTagHelperWritingScope, EndTagHelperWritingScope);
             __Microsoft_AspNet_Mvc_Razor_InputTestTagHelper = CreateTagHelper<Microsoft.AspNet.Mvc.Razor.InputTestTagHelper>();
             __tagHelperExecutionContext.Add(__Microsoft_AspNet_Mvc_Razor_InputTestTagHelper);
 #line 5 "TestFiles/Input/ModelExpressionTagHelper.cshtml"
@@ -59,20 +59,20 @@ __Microsoft_AspNet_Mvc_Razor_InputTestTagHelper.For = CreateModelExpression(__mo
             __tagHelperExecutionContext.AddTagHelperAttribute("for", __Microsoft_AspNet_Mvc_Razor_InputTestTagHelper.For);
             __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
             WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
-            WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
-            if (__tagHelperExecutionContext.Output.ContentSet)
+            Write(__tagHelperExecutionContext.Output.GeneratePreContent());
+            if (__tagHelperExecutionContext.Output.IsContentModified)
             {
-                WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+                Write(__tagHelperExecutionContext.Output.GenerateContent());
             }
             else if (__tagHelperExecutionContext.ChildContentRetrieved)
             {
-                WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+                Write(__tagHelperExecutionContext.GetChildContentAsync().Result);
             }
             else
             {
                 __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
             }
-            WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
+            Write(__tagHelperExecutionContext.Output.GeneratePostContent());
             WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
             __tagHelperExecutionContext = __tagHelperScopeManager.End();
             BeginContext(146, 2, true);
@@ -80,7 +80,7 @@ __Microsoft_AspNet_Mvc_Razor_InputTestTagHelper.For = CreateModelExpression(__mo
             EndContext();
             __tagHelperExecutionContext = __tagHelperScopeManager.Begin("input-test", true, "test", async() => {
             }
-            , StartWritingScope, EndWritingScope);
+            , StartTagHelperWritingScope, EndTagHelperWritingScope);
             __Microsoft_AspNet_Mvc_Razor_InputTestTagHelper = CreateTagHelper<Microsoft.AspNet.Mvc.Razor.InputTestTagHelper>();
             __tagHelperExecutionContext.Add(__Microsoft_AspNet_Mvc_Razor_InputTestTagHelper);
 #line 6 "TestFiles/Input/ModelExpressionTagHelper.cshtml"
@@ -91,20 +91,20 @@ __Microsoft_AspNet_Mvc_Razor_InputTestTagHelper.For = CreateModelExpression(__mo
             __tagHelperExecutionContext.AddTagHelperAttribute("for", __Microsoft_AspNet_Mvc_Razor_InputTestTagHelper.For);
             __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
             WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
-            WriteLiteral(__tagHelperExecutionContext.Output.GeneratePreContent());
-            if (__tagHelperExecutionContext.Output.ContentSet)
+            Write(__tagHelperExecutionContext.Output.GeneratePreContent());
+            if (__tagHelperExecutionContext.Output.IsContentModified)
             {
-                WriteLiteral(__tagHelperExecutionContext.Output.GenerateContent());
+                Write(__tagHelperExecutionContext.Output.GenerateContent());
             }
             else if (__tagHelperExecutionContext.ChildContentRetrieved)
             {
-                WriteLiteral(__tagHelperExecutionContext.GetChildContentAsync().Result);
+                Write(__tagHelperExecutionContext.GetChildContentAsync().Result);
             }
             else
             {
                 __tagHelperExecutionContext.ExecuteChildContentAsync().Wait();
             }
-            WriteLiteral(__tagHelperExecutionContext.Output.GeneratePostContent());
+            Write(__tagHelperExecutionContext.Output.GeneratePostContent());
             WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
             __tagHelperExecutionContext = __tagHelperScopeManager.End();
         }
diff --git a/test/Microsoft.AspNet.Mvc.Razor.Test/RazorPageTest.cs b/test/Microsoft.AspNet.Mvc.Razor.Test/RazorPageTest.cs
index c08a9e9449..e474c1c22e 100644
--- a/test/Microsoft.AspNet.Mvc.Razor.Test/RazorPageTest.cs
+++ b/test/Microsoft.AspNet.Mvc.Razor.Test/RazorPageTest.cs
@@ -9,6 +9,7 @@ using System.Threading.Tasks;
 using Microsoft.AspNet.Http.Core;
 using Microsoft.AspNet.Mvc.Rendering;
 using Microsoft.AspNet.PageExecutionInstrumentation;
+using Microsoft.AspNet.Razor.Runtime.TagHelpers;
 using Microsoft.AspNet.Testing;
 using Microsoft.Framework.WebEncoders;
 using Moq;
@@ -31,10 +32,10 @@ namespace Microsoft.AspNet.Mvc.Razor
             {
                 v.HtmlEncoder = new HtmlEncoder();
                 v.Write("Hello Prefix");
-                v.StartWritingScope();
+                v.StartTagHelperWritingScope();
                 v.Write("Hello from Output");
                 v.ViewContext.Writer.Write("Hello from view context writer");
-                var scopeValue = v.EndWritingScope();
+                var scopeValue = v.EndTagHelperWritingScope();
                 v.Write("From Scope: " + scopeValue.ToString());
             });
 
@@ -55,9 +56,9 @@ namespace Microsoft.AspNet.Mvc.Razor
             {
                 v.HtmlEncoder = new HtmlEncoder();
                 v.Write("Hello Prefix");
-                v.StartWritingScope();
+                v.StartTagHelperWritingScope();
                 v.Write("Hello In Scope");
-                var scopeValue = v.EndWritingScope();
+                var scopeValue = v.EndTagHelperWritingScope();
                 v.Write("From Scope: " + scopeValue.ToString());
             });
 
@@ -78,15 +79,15 @@ namespace Microsoft.AspNet.Mvc.Razor
             {
                 v.HtmlEncoder = new HtmlEncoder();
                 v.Write("Hello Prefix");
-                v.StartWritingScope();
+                v.StartTagHelperWritingScope();
                 v.Write("Hello In Scope Pre Nest");
 
-                v.StartWritingScope();
+                v.StartTagHelperWritingScope();
                 v.Write("Hello In Nested Scope");
-                var scopeValue1 = v.EndWritingScope();
+                var scopeValue1 = v.EndTagHelperWritingScope();
 
                 v.Write("Hello In Scope Post Nest");
-                var scopeValue2 = v.EndWritingScope();
+                var scopeValue2 = v.EndTagHelperWritingScope();
 
                 v.Write("From Scopes: " + scopeValue2.ToString() + scopeValue1.ToString());
             });
@@ -106,7 +107,7 @@ namespace Microsoft.AspNet.Mvc.Razor
             var viewContext = CreateViewContext();
             var page = CreatePage(async v =>
             {
-                v.StartWritingScope();
+                v.StartTagHelperWritingScope();
                 await v.FlushAsync();
             });
 
@@ -125,7 +126,7 @@ namespace Microsoft.AspNet.Mvc.Razor
             var viewContext = CreateViewContext();
             var page = CreatePage(v =>
             {
-                v.EndWritingScope();
+                v.EndTagHelperWritingScope();
             });
 
             // Act
@@ -136,6 +137,50 @@ namespace Microsoft.AspNet.Mvc.Razor
             Assert.Equal("There is no active writing scope to end.", ex.Message);
         }
 
+        [Fact]
+        public async Task EndTagHelperWritingScope_ReturnsAppropriateContent()
+        {
+            // Arrange
+            var viewContext = CreateViewContext();
+
+            // Act
+            var page = CreatePage(v =>
+            {
+                v.HtmlEncoder = new HtmlEncoder();
+                v.StartTagHelperWritingScope();
+                v.Write("Hello World!");
+                var returnValue = v.EndTagHelperWritingScope();
+
+                // Assert
+                var content = Assert.IsType<DefaultTagHelperContent>(returnValue);
+                Assert.Equal("Hello World!", content.GetContent());
+            });
+            await page.ExecuteAsync();
+        }
+
+        [Fact]
+        public async Task EndTagHelperWritingScope_CopiesContent_IfRazorTextWriter()
+        {
+            // Arrange
+            var viewContext = CreateViewContext();
+
+            // Act
+            var page = CreatePage(v =>
+            {
+                v.HtmlEncoder = new HtmlEncoder();
+                v.StartTagHelperWritingScope(new RazorTextWriter(TextWriter.Null, Encoding.UTF8));
+                v.Write("Hello ");
+                v.Write("World!");
+                var returnValue = v.EndTagHelperWritingScope();
+
+                // Assert
+                var content = Assert.IsType<DefaultTagHelperContent>(returnValue);
+                Assert.Equal("Hello World!", content.GetContent());
+                Assert.Equal(new[] { "Hello ", "World!" }, content.AsArray());
+            }, viewContext);
+            await page.ExecuteAsync();
+        }
+
         [Fact]
         public async Task DefineSection_ThrowsIfSectionIsAlreadyDefined()
         {
@@ -642,6 +687,72 @@ namespace Microsoft.AspNet.Mvc.Razor
             Assert.Same(stringCollectionWriter.Buffer.BufferEntries, buffer.BufferEntries[1]);
         }
 
+        [Fact]
+        public async Task Write_ITextWriterCopyable_WritesContent()
+        {
+            // Arrange
+            // This writer uses BufferEntryCollection underneath and so can copy the buffer.
+            var writer = new StringCollectionTextWriter(Encoding.UTF8);
+            var context = CreateViewContext(writer);
+            var expectedContent = "Hello World!";
+            var contentToBeCopied = new DefaultTagHelperContent().SetContent("Hello ").Append("World!");
+
+            // Act
+            var page = CreatePage(p =>
+            {
+                p.Write((ITextWriterCopyable)contentToBeCopied);
+            }, context);
+            await page.ExecuteAsync();
+
+            // Assert
+            Assert.Equal(expectedContent, writer.ToString());
+            Assert.Equal(2, writer.Buffer.BufferEntries.Count);
+            var expectedList = new List<object>();
+            expectedList.Add("Hello ");
+            expectedList.Add("World!");
+            Assert.Equal(expectedList, writer.Buffer.BufferEntries);
+        }
+
+        [Fact]
+        public async Task Write_ITextWriterCopyable_WritesContent_AsString()
+        {
+            // Arrange
+            // This writer stores the data as a string.
+            var writer = new StringWriter();
+            var context = CreateViewContext(writer);
+            var expectedContent = "Hello World!";
+            var contentToBeCopied = new DefaultTagHelperContent().SetContent("Hello ").Append("World!");
+
+            // Act
+            var page = CreatePage(p =>
+            {
+                p.Write((ITextWriterCopyable)contentToBeCopied);
+            }, context);
+            await page.ExecuteAsync();
+
+            // Assert
+            Assert.Equal(expectedContent, writer.ToString());
+        }
+
+        [Fact]
+        public async Task WriteTo_ITextWriterCopyable_WritesContent_ToSpecifiedWriter()
+        {
+            // Arrange
+            var writer = new StringWriter();
+            var expectedContent = "Hello World!";
+            var contentToBeCopied = new DefaultTagHelperContent().SetContent("Hello ").Append("World!");
+
+            // Act
+            var page = CreatePage(p =>
+            {
+                p.WriteTo(writer, (ITextWriterCopyable)contentToBeCopied);
+            });
+            await page.ExecuteAsync();
+
+            // Assert
+            Assert.Equal(expectedContent, writer.ToString());
+        }
+
         private static TestableRazorPage CreatePage(Action<TestableRazorPage> executeAction,
                                                     ViewContext context = null)
         {
diff --git a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/AnchorTagHelperTest.cs b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/AnchorTagHelperTest.cs
index 6ae60ee1b1..51544a5c16 100644
--- a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/AnchorTagHelperTest.cs
+++ b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/AnchorTagHelperTest.cs
@@ -35,7 +35,12 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 },
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something Else"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something Else");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var output = new TagHelperOutput(
                 expectedTagName,
                 attributes: new Dictionary<string, string>
@@ -43,10 +48,8 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                     { "id", "myanchor" },
                     { "asp-route-foo", "bar" },
                 },
-                htmlEncoder: new HtmlEncoder())
-            {
-                Content = "Something"
-            };
+                htmlEncoder: new HtmlEncoder());
+            output.Content.SetContent("Something");
 
             var urlHelper = new Mock<IUrlHelper>();
             urlHelper
@@ -75,7 +78,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             Assert.Equal("myanchor", attribute.Value);
             attribute = Assert.Single(output.Attributes, kvp => kvp.Key.Equals("href"));
             Assert.Equal("home/index", attribute.Value);
-            Assert.Equal("Something", output.Content);
+            Assert.Equal("Something", output.Content.GetContent());
             Assert.Equal(expectedTagName, output.TagName);
         }
 
@@ -87,14 +90,17 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 allAttributes: new Dictionary<string, object>(),
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var output = new TagHelperOutput(
                 "a",
                 attributes: new Dictionary<string, string>(),
-                htmlEncoder: new HtmlEncoder())
-            {
-                Content = string.Empty
-            };
+                htmlEncoder: new HtmlEncoder());
+            output.Content.SetContent(string.Empty);
 
             var generator = new Mock<IHtmlGenerator>(MockBehavior.Strict);
             generator
@@ -116,7 +122,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             generator.Verify();
             Assert.Equal("a", output.TagName);
             Assert.Empty(output.Attributes);
-            Assert.Empty(output.Content);
+            Assert.True(output.Content.IsEmpty);
         }
 
         [Fact]
@@ -127,14 +133,17 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 allAttributes: new Dictionary<string, object>(),
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var output = new TagHelperOutput(
                 "a",
                 attributes: new Dictionary<string, string>(),
-                htmlEncoder: new HtmlEncoder())
-            {
-                Content = string.Empty
-            };
+                htmlEncoder: new HtmlEncoder());
+            output.Content.SetContent(string.Empty);
 
             var generator = new Mock<IHtmlGenerator>();
             generator
@@ -157,7 +166,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             generator.Verify();
             Assert.Equal("a", output.TagName);
             Assert.Empty(output.Attributes);
-            Assert.Empty(output.Content);
+            Assert.True(output.Content.IsEmpty);
         }
 
         [Theory]
diff --git a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/CacheTagHelperTest.cs b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/CacheTagHelperTest.cs
index 6c6ace5e4e..cbbb25963b 100644
--- a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/CacheTagHelperTest.cs
+++ b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/CacheTagHelperTest.cs
@@ -259,10 +259,10 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             await cacheTagHelper1.ProcessAsync(tagHelperContext1, tagHelperOutput1);
 
             // Assert - 1
-            Assert.Null(tagHelperOutput1.PreContent);
-            Assert.Null(tagHelperOutput1.PostContent);
-            Assert.True(tagHelperOutput1.ContentSet);
-            Assert.Equal(childContent, tagHelperOutput1.Content);
+            Assert.Empty(tagHelperOutput1.PreContent.GetContent());
+            Assert.Empty(tagHelperOutput1.PostContent.GetContent());
+            Assert.True(tagHelperOutput1.IsContentModified);
+            Assert.Equal(childContent, tagHelperOutput1.Content.GetContent());
 
             // Arrange - 2
             var tagHelperContext2 = GetTagHelperContext(id, "different-content");
@@ -280,10 +280,10 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             await cacheTagHelper2.ProcessAsync(tagHelperContext2, tagHelperOutput2);
 
             // Assert - 2
-            Assert.Null(tagHelperOutput2.PreContent);
-            Assert.Null(tagHelperOutput2.PostContent);
-            Assert.True(tagHelperOutput2.ContentSet);
-            Assert.Equal(childContent, tagHelperOutput2.Content);
+            Assert.Empty(tagHelperOutput2.PreContent.GetContent());
+            Assert.Empty(tagHelperOutput2.PostContent.GetContent());
+            Assert.True(tagHelperOutput2.IsContentModified);
+            Assert.Equal(childContent, tagHelperOutput2.Content.GetContent());
         }
 
         [Fact]
@@ -296,11 +296,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             var tagHelperContext1 = GetTagHelperContext(id, childContent1);
             var tagHelperOutput1 = new TagHelperOutput("cache",
                                                        new Dictionary<string, string> { { "attr", "value" } },
-                                                       new HtmlEncoder())
-            {
-                PreContent = "<cache>",
-                PostContent = "</cache>"
-            };
+                                                       new HtmlEncoder());
+            tagHelperOutput1.PreContent.Append("<cache>");
+            tagHelperOutput1.PostContent.SetContent("</cache>");
             var cacheTagHelper1 = new CacheTagHelper
             {
                 VaryByCookie = "cookie1,cookie2",
@@ -313,21 +311,20 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             await cacheTagHelper1.ProcessAsync(tagHelperContext1, tagHelperOutput1);
 
             // Assert - 1
-            Assert.Null(tagHelperOutput1.PreContent);
-            Assert.Null(tagHelperOutput1.PostContent);
-            Assert.True(tagHelperOutput1.ContentSet);
-            Assert.Equal(childContent1, tagHelperOutput1.Content);
+            Assert.Empty(tagHelperOutput1.PreContent.GetContent());
+            Assert.Empty(tagHelperOutput1.PostContent.GetContent());
+            Assert.True(tagHelperOutput1.IsContentModified);
+            Assert.Equal(childContent1, tagHelperOutput1.Content.GetContent());
 
             // Arrange - 2
             var childContent2 = "different-content";
             var tagHelperContext2 = GetTagHelperContext(id, childContent2);
-            var tagHelperOutput2 = new TagHelperOutput("cache",
-                                                       new Dictionary<string, string> { { "attr", "value" } },
-                                                       new HtmlEncoder())
-            {
-                PreContent = "<cache>",
-                PostContent = "</cache>"
-            };
+            var tagHelperOutput2 = new TagHelperOutput(
+                "cache",
+                new Dictionary<string, string> { { "attr", "value" } },
+                new HtmlEncoder());
+            tagHelperOutput2.PreContent.SetContent("<cache>");
+            tagHelperOutput2.PostContent.SetContent("</cache>");
             var cacheTagHelper2 = new CacheTagHelper
             {
                 VaryByCookie = "cookie1,cookie2",
@@ -340,10 +337,10 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             await cacheTagHelper2.ProcessAsync(tagHelperContext2, tagHelperOutput2);
 
             // Assert - 2
-            Assert.Null(tagHelperOutput2.PreContent);
-            Assert.Null(tagHelperOutput2.PostContent);
-            Assert.True(tagHelperOutput2.ContentSet);
-            Assert.Equal(childContent2, tagHelperOutput2.Content);
+            Assert.Empty(tagHelperOutput2.PreContent.GetContent());
+            Assert.Empty(tagHelperOutput2.PostContent.GetContent());
+            Assert.True(tagHelperOutput2.IsContentModified);
+            Assert.Equal(childContent2, tagHelperOutput2.Content.GetContent());
         }
 
         [Fact]
@@ -536,11 +533,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             var tagHelperContext1 = GetTagHelperContext(id, childContent1);
             var tagHelperOutput1 = new TagHelperOutput("cache",
                                                        new Dictionary<string, string> { { "attr", "value" } },
-                                                       new HtmlEncoder())
-            {
-                PreContent = "<cache>",
-                PostContent = "</cache>"
-            };
+                                                       new HtmlEncoder());
+            tagHelperOutput1.PreContent.SetContent("<cache>");
+            tagHelperOutput1.PostContent.SetContent("</cache>");
             var cacheTagHelper1 = new CacheTagHelper
             {
                 ViewContext = GetViewContext(),
@@ -552,21 +547,19 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             await cacheTagHelper1.ProcessAsync(tagHelperContext1, tagHelperOutput1);
 
             // Assert - 1
-            Assert.Null(tagHelperOutput1.PreContent);
-            Assert.Null(tagHelperOutput1.PostContent);
-            Assert.True(tagHelperOutput1.ContentSet);
-            Assert.Equal(childContent1, tagHelperOutput1.Content);
+            Assert.Empty(tagHelperOutput1.PreContent.GetContent());
+            Assert.Empty(tagHelperOutput1.PostContent.GetContent());
+            Assert.True(tagHelperOutput1.IsContentModified);
+            Assert.Equal(childContent1, tagHelperOutput1.Content.GetContent());
 
             // Arrange - 2
             var childContent2 = "different-content";
             var tagHelperContext2 = GetTagHelperContext(id, childContent2);
             var tagHelperOutput2 = new TagHelperOutput("cache",
                                                        new Dictionary<string, string> { { "attr", "value" } },
-                                                       new HtmlEncoder())
-            {
-                PreContent = "<cache>",
-                PostContent = "</cache>"
-            };
+                                                       new HtmlEncoder());
+            tagHelperOutput2.PreContent.SetContent("<cache>");
+            tagHelperOutput2.PostContent.SetContent("</cache>");
             var cacheTagHelper2 = new CacheTagHelper
             {
                 ViewContext = GetViewContext(),
@@ -579,10 +572,10 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             await cacheTagHelper2.ProcessAsync(tagHelperContext2, tagHelperOutput2);
 
             // Assert - 2
-            Assert.Null(tagHelperOutput2.PreContent);
-            Assert.Null(tagHelperOutput2.PostContent);
-            Assert.True(tagHelperOutput2.ContentSet);
-            Assert.Equal(childContent2, tagHelperOutput2.Content);
+            Assert.Empty(tagHelperOutput2.PreContent.GetContent());
+            Assert.Empty(tagHelperOutput2.PostContent.GetContent());
+            Assert.True(tagHelperOutput2.IsContentModified);
+            Assert.Equal(childContent2, tagHelperOutput2.Content.GetContent());
         }
 
         [Fact]
@@ -599,11 +592,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             var tagHelperContext1 = GetTagHelperContext(id, childContent1);
             var tagHelperOutput1 = new TagHelperOutput("cache",
                                                        new Dictionary<string, string> { { "attr", "value" } },
-                                                       new HtmlEncoder())
-            {
-                PreContent = "<cache>",
-                PostContent = "</cache>"
-            };
+                                                       new HtmlEncoder());
+            tagHelperOutput1.PreContent.SetContent("<cache>");
+            tagHelperOutput1.PostContent.SetContent("</cache>");
             var cacheTagHelper1 = new CacheTagHelper
             {
                 ViewContext = GetViewContext(),
@@ -615,10 +606,10 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             await cacheTagHelper1.ProcessAsync(tagHelperContext1, tagHelperOutput1);
 
             // Assert - 1
-            Assert.Null(tagHelperOutput1.PreContent);
-            Assert.Null(tagHelperOutput1.PostContent);
-            Assert.True(tagHelperOutput1.ContentSet);
-            Assert.Equal(childContent1, tagHelperOutput1.Content);
+            Assert.Empty(tagHelperOutput1.PreContent.GetContent());
+            Assert.Empty(tagHelperOutput1.PostContent.GetContent());
+            Assert.True(tagHelperOutput1.IsContentModified);
+            Assert.Equal(childContent1, tagHelperOutput1.Content.GetContent());
 
             // Arrange - 2
             currentTime = currentTime.AddMinutes(5).AddSeconds(2);
@@ -626,11 +617,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             var tagHelperContext2 = GetTagHelperContext(id, childContent2);
             var tagHelperOutput2 = new TagHelperOutput("cache",
                                                        new Dictionary<string, string> { { "attr", "value" } },
-                                                       new HtmlEncoder())
-            {
-                PreContent = "<cache>",
-                PostContent = "</cache>"
-            };
+                                                       new HtmlEncoder());
+            tagHelperOutput2.PreContent.SetContent("<cache>");
+            tagHelperOutput2.PostContent.SetContent("</cache>");
             var cacheTagHelper2 = new CacheTagHelper
             {
                 ViewContext = GetViewContext(),
@@ -642,10 +631,10 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             await cacheTagHelper2.ProcessAsync(tagHelperContext2, tagHelperOutput2);
 
             // Assert - 2
-            Assert.Null(tagHelperOutput2.PreContent);
-            Assert.Null(tagHelperOutput2.PostContent);
-            Assert.True(tagHelperOutput2.ContentSet);
-            Assert.Equal(childContent2, tagHelperOutput2.Content);
+            Assert.Empty(tagHelperOutput2.PreContent.GetContent());
+            Assert.Empty(tagHelperOutput2.PostContent.GetContent());
+            Assert.True(tagHelperOutput2.IsContentModified);
+            Assert.Equal(childContent2, tagHelperOutput2.Content.GetContent());
         }
 
         [Fact]
@@ -662,11 +651,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             var tagHelperContext1 = GetTagHelperContext(id, childContent1);
             var tagHelperOutput1 = new TagHelperOutput("cache",
                                                        new Dictionary<string, string> { { "attr", "value" } },
-                                                       new HtmlEncoder())
-            {
-                PreContent = "<cache>",
-                PostContent = "</cache>"
-            };
+                                                       new HtmlEncoder());
+            tagHelperOutput1.PreContent.SetContent("<cache>");
+            tagHelperOutput1.PostContent.SetContent("</cache>");
             var cacheTagHelper1 = new CacheTagHelper
             {
                 ViewContext = GetViewContext(),
@@ -678,10 +665,10 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             await cacheTagHelper1.ProcessAsync(tagHelperContext1, tagHelperOutput1);
 
             // Assert - 1
-            Assert.Null(tagHelperOutput1.PreContent);
-            Assert.Null(tagHelperOutput1.PostContent);
-            Assert.True(tagHelperOutput1.ContentSet);
-            Assert.Equal(childContent1, tagHelperOutput1.Content);
+            Assert.Empty(tagHelperOutput1.PreContent.GetContent());
+            Assert.Empty(tagHelperOutput1.PostContent.GetContent());
+            Assert.True(tagHelperOutput1.IsContentModified);
+            Assert.Equal(childContent1, tagHelperOutput1.Content.GetContent());
 
             // Arrange - 2
             currentTime = currentTime.AddSeconds(35);
@@ -689,11 +676,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             var tagHelperContext2 = GetTagHelperContext(id, childContent2);
             var tagHelperOutput2 = new TagHelperOutput("cache",
                                                        new Dictionary<string, string> { { "attr", "value" } },
-                                                       new HtmlEncoder())
-            {
-                PreContent = "<cache>",
-                PostContent = "</cache>"
-            };
+                                                       new HtmlEncoder());
+            tagHelperOutput2.PreContent.SetContent("<cache>");
+            tagHelperOutput2.PostContent.SetContent("</cache>");
             var cacheTagHelper2 = new CacheTagHelper
             {
                 ViewContext = GetViewContext(),
@@ -705,10 +690,10 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             await cacheTagHelper2.ProcessAsync(tagHelperContext2, tagHelperOutput2);
 
             // Assert - 2
-            Assert.Null(tagHelperOutput2.PreContent);
-            Assert.Null(tagHelperOutput2.PostContent);
-            Assert.True(tagHelperOutput2.ContentSet);
-            Assert.Equal(childContent2, tagHelperOutput2.Content);
+            Assert.Empty(tagHelperOutput2.PreContent.GetContent());
+            Assert.Empty(tagHelperOutput2.PostContent.GetContent());
+            Assert.True(tagHelperOutput2.IsContentModified);
+            Assert.Equal(childContent2, tagHelperOutput2.Content.GetContent());
         }
 
         [Fact]
@@ -716,7 +701,8 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         {
             // Arrange
             var id = "some-id";
-            var expectedContent = "some-content";
+            var expectedContent = new DefaultTagHelperContent();
+            expectedContent.SetContent("some-content");
             var tokenSource = new CancellationTokenSource();
             var cache = new MemoryCache(new MemoryCacheOptions());
             var tagHelperContext = new TagHelperContext(
@@ -731,15 +717,13 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                     {
                         new CancellationTokenTrigger(tokenSource.Token)
                     });
-                    return Task.FromResult(expectedContent);
+                    return Task.FromResult<TagHelperContent>(expectedContent);
                 });
             var tagHelperOutput = new TagHelperOutput("cache",
                                                        new Dictionary<string, string> { { "attr", "value" } },
-                                                       new HtmlEncoder())
-            {
-                PreContent = "<cache>",
-                PostContent = "</cache>"
-            };
+                                                       new HtmlEncoder());
+            tagHelperOutput.PreContent.SetContent("<cache>");
+            tagHelperOutput.PostContent.SetContent("</cache>");
             var cacheTagHelper = new CacheTagHelper
             {
                 ViewContext = GetViewContext(),
@@ -749,11 +733,11 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
 
             // Act - 1
             await cacheTagHelper.ProcessAsync(tagHelperContext, tagHelperOutput);
-            string cachedValue;
+            TagHelperContent cachedValue;
             var result = cache.TryGetValue(key, out cachedValue);
 
             // Assert - 1
-            Assert.Equal(expectedContent, tagHelperOutput.Content);
+            Assert.Equal(expectedContent.GetContent(), tagHelperOutput.Content.GetContent());
             Assert.True(result);
             Assert.Equal(expectedContent, cachedValue);
 
@@ -782,7 +766,12 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 allAttributes: new Dictionary<string, object>(),
                 items: new Dictionary<object, object>(),
                 uniqueId: id,
-                getChildContentAsync: () => Task.FromResult(childContent));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent(childContent);
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
         }
 
         private static string GetHashedBytes(string input)
diff --git a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/EnvironmentTagHelperTest.cs b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/EnvironmentTagHelperTest.cs
index 8dd846c22b..3540064d66 100644
--- a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/EnvironmentTagHelperTest.cs
+++ b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/EnvironmentTagHelperTest.cs
@@ -98,10 +98,10 @@ namespace Microsoft.AspNet.Mvc.TagHelpers.Test
 
             // Assert
             Assert.Null(output.TagName);
-            Assert.Null(output.PreContent);
-            Assert.Null(output.Content);
-            Assert.Null(output.PostContent);
-            Assert.True(output.ContentSet);
+            Assert.Empty(output.PreContent.GetContent());
+            Assert.True(output.Content.IsEmpty);
+            Assert.Empty(output.PostContent.GetContent());
+            Assert.True(output.IsContentModified);
         }
 
         private void ShouldShowContent(string namesAttribute, string environmentName)
@@ -126,7 +126,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers.Test
 
             // Assert
             Assert.Null(output.TagName);
-            Assert.False(output.ContentSet);
+            Assert.False(output.IsContentModified);
         }
 
         private TagHelperContext MakeTagHelperContext(
@@ -139,7 +139,12 @@ namespace Microsoft.AspNet.Mvc.TagHelpers.Test
                 attributes,
                 items: new Dictionary<object, object>(),
                 uniqueId: Guid.NewGuid().ToString("N"),
-                getChildContentAsync: () => Task.FromResult(content));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent(content);
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
         }
 
         private TagHelperOutput MakeTagHelperOutput(string tagName, IDictionary<string, string> attributes = null)
diff --git a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/FormTagHelperTest.cs b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/FormTagHelperTest.cs
index 243e6bacb8..9079d5c24b 100644
--- a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/FormTagHelperTest.cs
+++ b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/FormTagHelperTest.cs
@@ -36,7 +36,12 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 },
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something Else"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something Else");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var output = new TagHelperOutput(
                 expectedTagName,
                 attributes: new Dictionary<string, string>
@@ -44,10 +49,8 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                     { "id", "myform" },
                     { "asp-route-foo", "bar" },
                 },
-                htmlEncoder: new HtmlEncoder())
-            {
-                PostContent = "Something"
-            };
+                htmlEncoder: new HtmlEncoder());
+            output.PostContent.SetContent("Something");
             var urlHelper = new Mock<IUrlHelper>();
             urlHelper
                 .Setup(mock => mock.Action(It.IsAny<UrlActionContext>())).Returns("home/index");
@@ -79,9 +82,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             Assert.Equal("post", attribute.Value);
             attribute = Assert.Single(output.Attributes, kvp => kvp.Key.Equals("action"));
             Assert.Equal("home/index", attribute.Value);
-            Assert.Empty(output.PreContent);
-            Assert.Empty(output.Content);
-            Assert.Equal(expectedPostContent, output.PostContent);
+            Assert.Empty(output.PreContent.GetContent());
+            Assert.True(output.Content.IsEmpty);
+            Assert.Equal(expectedPostContent, output.PostContent.GetContent());
             Assert.Equal(expectedTagName, output.TagName);
         }
 
@@ -97,7 +100,12 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 allAttributes: new Dictionary<string, object>(),
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var output = new TagHelperOutput(
                 "form",
                 attributes: new Dictionary<string, string>(),
@@ -130,9 +138,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             Assert.Equal("form", output.TagName);
             Assert.False(output.SelfClosing);
             Assert.Empty(output.Attributes);
-            Assert.Empty(output.PreContent);
-            Assert.Empty(output.Content);
-            Assert.Equal(expectedPostContent, output.PostContent);
+            Assert.Empty(output.PreContent.GetContent());
+            Assert.True(output.Content.IsEmpty);
+            Assert.Equal(expectedPostContent, output.PostContent.GetContent());
         }
 
         [Fact]
@@ -144,7 +152,12 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 allAttributes: new Dictionary<string, object>(),
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var expectedAttribute = new KeyValuePair<string, string>("asp-ROUTEE-NotRoute", "something");
             var output = new TagHelperOutput(
                 "form",
@@ -196,9 +209,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             Assert.False(output.SelfClosing);
             var attribute = Assert.Single(output.Attributes);
             Assert.Equal(expectedAttribute, attribute);
-            Assert.Empty(output.PreContent);
-            Assert.Empty(output.Content);
-            Assert.Empty(output.PostContent);
+            Assert.Empty(output.PreContent.GetContent());
+            Assert.True(output.Content.IsEmpty);
+            Assert.Empty(output.PostContent.GetContent());
             generator.Verify();
         }
 
@@ -211,7 +224,12 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 allAttributes: new Dictionary<string, object>(),
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var output = new TagHelperOutput(
                 "form",
                 attributes: new Dictionary<string, string>(),
@@ -238,9 +256,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             Assert.Equal("form", output.TagName);
             Assert.False(output.SelfClosing);
             Assert.Empty(output.Attributes);
-            Assert.Empty(output.PreContent);
-            Assert.Empty(output.Content);
-            Assert.Empty(output.PostContent);
+            Assert.Empty(output.PreContent.GetContent());
+            Assert.True(output.Content.IsEmpty);
+            Assert.Empty(output.PostContent.GetContent());
         }
 
         [Theory]
@@ -268,7 +286,12 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 },
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
 
             // Act
             await formTagHelper.ProcessAsync(context, output);
@@ -280,9 +303,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             Assert.Equal(htmlAction, attribute.Value);
             attribute = Assert.Single(output.Attributes, kvp => kvp.Key.Equals("METhod"));
             Assert.Equal("POST", attribute.Value);
-            Assert.Empty(output.PreContent);
-            Assert.Empty(output.Content);
-            Assert.Empty(output.PostContent);
+            Assert.Empty(output.PreContent.GetContent());
+            Assert.True(output.Content.IsEmpty);
+            Assert.Empty(output.PostContent.GetContent());
         }
 
         [Theory]
@@ -316,7 +339,12 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 allAttributes: new Dictionary<string, object>(),
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
 
 
             // Act
@@ -327,9 +355,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             Assert.False(output.SelfClosing);
             var attribute = Assert.Single(output.Attributes);
             Assert.Equal(new KeyValuePair<string, string>("aCTiON", "my-action"), attribute);
-            Assert.Empty(output.PreContent);
-            Assert.Empty(output.Content);
-            Assert.Equal(expectedPostContent, output.PostContent);
+            Assert.Empty(output.PreContent.GetContent());
+            Assert.True(output.Content.IsEmpty);
+            Assert.Equal(expectedPostContent, output.PostContent.GetContent());
         }
 
         [Theory]
diff --git a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/InputTagHelperTest.cs b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/InputTagHelperTest.cs
index 5e00270ea8..4db0ea1581 100644
--- a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/InputTagHelperTest.cs
+++ b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/InputTagHelperTest.cs
@@ -99,18 +99,23 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 allAttributes: new Dictionary<string, object>(),
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var originalAttributes = new Dictionary<string, string>
             {
                 { "class", "form-control" },
             };
             var output = new TagHelperOutput(expectedTagName, originalAttributes, new HtmlEncoder())
             {
-                PreContent = expectedPreContent,
-                Content = expectedContent,
-                PostContent = expectedPostContent,
                 SelfClosing = false,
             };
+            output.PreContent.SetContent(expectedPreContent);
+            output.Content.SetContent(expectedContent);
+            output.PostContent.SetContent(expectedPostContent);
 
             var htmlGenerator = new TestableHtmlGenerator(new EmptyModelMetadataProvider())
             {
@@ -134,9 +139,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
 
             // Assert
             Assert.Equal(expectedAttributes, output.Attributes);
-            Assert.Equal(expectedPreContent, output.PreContent);
-            Assert.Equal(expectedContent, output.Content);
-            Assert.Equal(expectedPostContent, output.PostContent);
+            Assert.Equal(expectedPreContent, output.PreContent.GetContent());
+            Assert.Equal(expectedContent, output.Content.GetContent());
+            Assert.Equal(expectedPostContent, output.PostContent.GetContent());
             Assert.False(output.SelfClosing);
             Assert.Equal(expectedTagName, output.TagName);
         }
@@ -155,18 +160,23 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 allAttributes: new Dictionary<string, object>(),
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var originalAttributes = new Dictionary<string, string>
             {
                 { "class", "form-control" },
             };
             var output = new TagHelperOutput(originalTagName, originalAttributes, new HtmlEncoder())
             {
-                PreContent = expectedPreContent,
-                Content = originalContent,
-                PostContent = expectedPostContent,
                 SelfClosing = true,
             };
+            output.PreContent.SetContent(expectedPreContent);
+            output.Content.SetContent(originalContent);
+            output.PostContent.SetContent(expectedPostContent);
 
             var htmlGenerator = new Mock<IHtmlGenerator>(MockBehavior.Strict);
             var tagHelper = GetTagHelper(htmlGenerator.Object, model: false, propertyName: nameof(Model.IsACar));
@@ -201,9 +211,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             htmlGenerator.Verify();
 
             Assert.Empty(output.Attributes);    // Moved to Content and cleared
-            Assert.Equal(expectedPreContent, output.PreContent);
-            Assert.Equal(expectedContent, output.Content);
-            Assert.Equal(expectedPostContent, output.PostContent);
+            Assert.Equal(expectedPreContent, output.PreContent.GetContent());
+            Assert.Equal(expectedContent, output.Content.GetContent());
+            Assert.Equal(expectedPostContent, output.PostContent.GetContent());
             Assert.True(output.SelfClosing);
             Assert.Null(output.TagName);       // Cleared
         }
@@ -246,18 +256,23 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 allAttributes: contextAttributes,
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var originalAttributes = new Dictionary<string, string>
             {
                 { "class", "form-control" },
             };
             var output = new TagHelperOutput(expectedTagName, originalAttributes, new HtmlEncoder())
             {
-                PreContent = expectedPreContent,
-                Content = expectedContent,
-                PostContent = expectedPostContent,
                 SelfClosing = false,
             };
+            output.PreContent.SetContent(expectedPreContent);
+            output.Content.SetContent(expectedContent);
+            output.PostContent.SetContent(expectedPostContent);
 
             var htmlGenerator = new Mock<IHtmlGenerator>(MockBehavior.Strict);
             var tagHelper = GetTagHelper(htmlGenerator.Object, model, nameof(Model.Text));
@@ -290,9 +305,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
 
             Assert.False(output.SelfClosing);
             Assert.Equal(expectedAttributes, output.Attributes);
-            Assert.Equal(expectedPreContent, output.PreContent);
-            Assert.Equal(expectedContent, output.Content);
-            Assert.Equal(expectedPostContent, output.PostContent);
+            Assert.Equal(expectedPreContent, output.PreContent.GetContent());
+            Assert.Equal(expectedContent, output.Content.GetContent());
+            Assert.Equal(expectedPostContent, output.PostContent.GetContent());
             Assert.Equal(expectedTagName, output.TagName);
         }
 
@@ -334,18 +349,23 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 allAttributes: contextAttributes,
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var originalAttributes = new Dictionary<string, string>
             {
                 { "class", "form-control" },
             };
             var output = new TagHelperOutput(expectedTagName, originalAttributes, new HtmlEncoder())
             {
-                PreContent = expectedPreContent,
-                Content = expectedContent,
-                PostContent = expectedPostContent,
                 SelfClosing = false,
             };
+            output.PreContent.SetContent(expectedPreContent);
+            output.Content.SetContent(expectedContent);
+            output.PostContent.SetContent(expectedPostContent);
 
             var htmlGenerator = new Mock<IHtmlGenerator>(MockBehavior.Strict);
             var tagHelper = GetTagHelper(htmlGenerator.Object, model, nameof(Model.Text));
@@ -377,9 +397,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
 
             Assert.False(output.SelfClosing);
             Assert.Equal(expectedAttributes, output.Attributes);
-            Assert.Equal(expectedPreContent, output.PreContent);
-            Assert.Equal(expectedContent, output.Content);
-            Assert.Equal(expectedPostContent, output.PostContent);
+            Assert.Equal(expectedPreContent, output.PreContent.GetContent());
+            Assert.Equal(expectedContent, output.Content.GetContent());
+            Assert.Equal(expectedPostContent, output.PostContent.GetContent());
             Assert.Equal(expectedTagName, output.TagName);
         }
 
@@ -419,18 +439,23 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 allAttributes: contextAttributes,
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var originalAttributes = new Dictionary<string, string>
             {
                 { "class", "form-control" },
             };
             var output = new TagHelperOutput(expectedTagName, originalAttributes, new HtmlEncoder())
             {
-                PreContent = expectedPreContent,
-                Content = expectedContent,
-                PostContent = expectedPostContent,
                 SelfClosing = false,
             };
+            output.PreContent.SetContent(expectedPreContent);
+            output.Content.SetContent(expectedContent);
+            output.PostContent.SetContent(expectedPostContent);
 
             var htmlGenerator = new Mock<IHtmlGenerator>(MockBehavior.Strict);
             var tagHelper = GetTagHelper(htmlGenerator.Object, model, nameof(Model.Text));
@@ -463,9 +488,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
 
             Assert.False(output.SelfClosing);
             Assert.Equal(expectedAttributes, output.Attributes);
-            Assert.Equal(expectedPreContent, output.PreContent);
-            Assert.Equal(expectedContent, output.Content);
-            Assert.Equal(expectedPostContent, output.PostContent);
+            Assert.Equal(expectedPreContent, output.PreContent.GetContent());
+            Assert.Equal(expectedContent, output.Content.GetContent());
+            Assert.Equal(expectedPostContent, output.PostContent.GetContent());
             Assert.Equal(expectedTagName, output.TagName);
         }
 
@@ -519,18 +544,23 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 allAttributes: contextAttributes,
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var originalAttributes = new Dictionary<string, string>
             {
                 { "class", "form-control" },
             };
             var output = new TagHelperOutput(expectedTagName, originalAttributes, new HtmlEncoder())
             {
-                PreContent = expectedPreContent,
-                Content = expectedContent,
-                PostContent = expectedPostContent,
                 SelfClosing = false,
             };
+            output.PreContent.SetContent(expectedPreContent);
+            output.Content.SetContent(expectedContent);
+            output.PostContent.SetContent(expectedPostContent);
 
             var htmlGenerator = new Mock<IHtmlGenerator>(MockBehavior.Strict);
             var tagHelper = GetTagHelper(htmlGenerator.Object, model, nameof(Model.Text));
@@ -563,9 +593,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
 
             Assert.False(output.SelfClosing);
             Assert.Equal(expectedAttributes, output.Attributes);
-            Assert.Equal(expectedPreContent, output.PreContent);
-            Assert.Equal(expectedContent, output.Content);
-            Assert.Equal(expectedPostContent, output.PostContent);
+            Assert.Equal(expectedPreContent, output.PreContent.GetContent());
+            Assert.Equal(expectedContent, output.Content.GetContent());
+            Assert.Equal(expectedPostContent, output.PostContent.GetContent());
             Assert.Equal(expectedTagName, output.TagName);
         }
 
@@ -588,14 +618,20 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 allAttributes: new Dictionary<string, object>(),
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
+
             var output = new TagHelperOutput(expectedTagName, expectedAttributes, new HtmlEncoder())
             {
-                PreContent = expectedPreContent,
-                Content = expectedContent,
-                PostContent = expectedPostContent,
                 SelfClosing = false,
             };
+            output.PreContent.SetContent(expectedPreContent);
+            output.Content.SetContent(expectedContent);
+            output.PostContent.SetContent(expectedPostContent);
 
             var htmlGenerator = new TestableHtmlGenerator(new EmptyModelMetadataProvider())
             {
@@ -612,9 +648,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
 
             // Assert
             Assert.Equal(expectedAttributes, output.Attributes);
-            Assert.Equal(expectedPreContent, output.PreContent);
-            Assert.Equal(expectedContent, output.Content);
-            Assert.Equal(expectedPostContent, output.PostContent);
+            Assert.Equal(expectedPreContent, output.PreContent.GetContent());
+            Assert.Equal(expectedContent, output.Content.GetContent());
+            Assert.Equal(expectedPostContent, output.PostContent.GetContent());
             Assert.False(output.SelfClosing);
             Assert.Equal(expectedTagName, output.TagName);
         }
@@ -644,7 +680,12 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 allAttributes: new Dictionary<string, object>(),
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var output = new TagHelperOutput(expectedTagName, originalAttributes, new HtmlEncoder());
             var tagHelper = new InputTagHelper
             {
diff --git a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/Internal/AttributeMatcherTest.cs b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/Internal/AttributeMatcherTest.cs
index 054a51446e..6853e0ddf7 100644
--- a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/Internal/AttributeMatcherTest.cs
+++ b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/Internal/AttributeMatcherTest.cs
@@ -128,7 +128,12 @@ namespace Microsoft.AspNet.Mvc.TagHelpers.Internal
                 attributes,
                 items: new Dictionary<object, object>(),
                 uniqueId: Guid.NewGuid().ToString("N"),
-                getChildContentAsync: () => Task.FromResult(content));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.Append(content);
+                    return Task.FromResult((TagHelperContent)tagHelperContent);
+                });
         }
     }
 }
\ No newline at end of file
diff --git a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/LabelTagHelperTest.cs b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/LabelTagHelperTest.cs
index 3aa5548bb5..29d2dcdee6 100644
--- a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/LabelTagHelperTest.cs
+++ b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/LabelTagHelperTest.cs
@@ -190,22 +190,25 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 allAttributes: new Dictionary<string, object>(),
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult(tagHelperOutputContent.OriginalChildContent));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent(tagHelperOutputContent.OriginalChildContent);
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var htmlAttributes = new Dictionary<string, string>
             {
                 { "class", "form-control" },
             };
-            var output = new TagHelperOutput(expectedTagName, htmlAttributes, new HtmlEncoder())
-            {
-                PreContent = expectedPreContent,
-                PostContent = expectedPostContent,
-            };
+            var output = new TagHelperOutput(expectedTagName, htmlAttributes, new HtmlEncoder());
+            output.PreContent.SetContent(expectedPreContent);
+            output.PostContent.SetContent(expectedPostContent);
 
-            // LabelTagHelper checks ContentSet so we don't want to forcibly set it if 
+            // LabelTagHelper checks IsContentModified so we don't want to forcibly set it if 
             // tagHelperOutputContent.OriginalContent is going to be null or empty.
             if (!string.IsNullOrEmpty(tagHelperOutputContent.OriginalContent))
             {
-                output.Content = tagHelperOutputContent.OriginalContent;
+                output.Content.SetContent(tagHelperOutputContent.OriginalContent);
             }
 
             var htmlGenerator = new TestableHtmlGenerator(metadataProvider);
@@ -218,9 +221,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
 
             // Assert
             Assert.Equal(expectedAttributes, output.Attributes);
-            Assert.Equal(expectedPreContent, output.PreContent);
-            Assert.Equal(tagHelperOutputContent.ExpectedContent, output.Content);
-            Assert.Equal(expectedPostContent, output.PostContent);
+            Assert.Equal(expectedPreContent, output.PreContent.GetContent());
+            Assert.Equal(tagHelperOutputContent.ExpectedContent, output.Content.GetContent());
+            Assert.Equal(expectedPostContent, output.PostContent.GetContent());
             Assert.False(output.SelfClosing);
             Assert.Equal(expectedTagName, output.TagName);
         }
@@ -250,13 +253,16 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 allAttributes: new Dictionary<string, object>(),
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
-            var output = new TagHelperOutput(expectedTagName, expectedAttributes, new HtmlEncoder())
-            {
-                PreContent = expectedPreContent,
-                Content = expectedContent,
-                PostContent = expectedPostContent,
-            };
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
+            var output = new TagHelperOutput(expectedTagName, expectedAttributes, new HtmlEncoder());
+            output.PreContent.SetContent(expectedPreContent);
+            output.Content.SetContent(expectedContent);
+            output.PostContent.SetContent(expectedPostContent);
 
             var htmlGenerator = new TestableHtmlGenerator(metadataProvider);
             Model model = null;
@@ -269,9 +275,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
 
             // Assert
             Assert.Equal(expectedAttributes, output.Attributes);
-            Assert.Equal(expectedPreContent, output.PreContent);
-            Assert.Equal(expectedContent, output.Content);
-            Assert.Equal(expectedPostContent, output.PostContent);
+            Assert.Equal(expectedPreContent, output.PreContent.GetContent());
+            Assert.Equal(expectedContent, output.Content.GetContent());
+            Assert.Equal(expectedPostContent, output.PostContent.GetContent());
             Assert.Equal(expectedTagName, output.TagName);
         }
 
diff --git a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/LinkTagHelperTest.cs b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/LinkTagHelperTest.cs
index e212222949..3e8e6a61e4 100644
--- a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/LinkTagHelperTest.cs
+++ b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/LinkTagHelperTest.cs
@@ -114,7 +114,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             // Assert
             Assert.Null(output.TagName);
             Assert.NotNull(output.Content);
-            Assert.True(output.ContentSet);
+            Assert.True(output.IsContentModified);
         }
 
         [Fact]
@@ -158,7 +158,8 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             helper.Process(context, output);
 
             // Assert
-            Assert.StartsWith("<link rel=\"stylesheet\" data-extra=\"something\" href=\"test.css\"", output.Content);
+            Assert.StartsWith(
+                "<link rel=\"stylesheet\" data-extra=\"something\" href=\"test.css\"", output.Content.GetContent());
         }
 
         public static TheoryData DoesNotRunWhenARequiredAttributeIsMissing_Data
@@ -258,7 +259,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
 
             // Assert
             Assert.NotNull(output.TagName);
-            Assert.False(output.ContentSet);
+            Assert.False(output.IsContentModified);
         }
 
         [Fact]
@@ -282,7 +283,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
 
             // Assert
             Assert.NotNull(output.TagName);
-            Assert.False(output.ContentSet);
+            Assert.False(output.IsContentModified);
         }
 
         [Fact]
@@ -322,7 +323,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
 
             // Assert
             Assert.Equal("<link href=\"/css/site.css\" rel=\"stylesheet\" />" +
-                         "<link href=\"/base.css\" rel=\"stylesheet\" />", output.Content);
+                         "<link href=\"/base.css\" rel=\"stylesheet\" />", output.Content.GetContent());
         }
 
         [Fact]
@@ -362,7 +363,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
 
             // Assert
             Assert.Equal("<link href=\"HtmlEncode[[/css/site.css]]\" rel=\"stylesheet\" />" +
-                         "<link href=\"HtmlEncode[[/base.css]]\" rel=\"stylesheet\" />", output.Content);
+                         "<link href=\"HtmlEncode[[/base.css]]\" rel=\"stylesheet\" />", output.Content.GetContent());
         }
 
         private static ViewContext MakeViewContext()
@@ -385,7 +386,12 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 attributes,
                 items: new Dictionary<object, object>(),
                 uniqueId: Guid.NewGuid().ToString("N"),
-                getChildContentAsync: () => Task.FromResult(content));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent(content);
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
         }
 
         private static TagHelperOutput MakeTagHelperOutput(string tagName, IDictionary<string, string> attributes = null)
diff --git a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/OptionTagHelperTest.cs b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/OptionTagHelperTest.cs
index 5a649c790b..4dad5e7a47 100644
--- a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/OptionTagHelperTest.cs
+++ b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/OptionTagHelperTest.cs
@@ -141,12 +141,17 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 contextAttributes,
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult(originalContent));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent(originalContent);
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var output = new TagHelperOutput(expectedTagName, originalAttributes, new HtmlEncoder())
             {
-                Content = originalContent,
                 SelfClosing = false,
             };
+            output.Content.SetContent(originalContent);
 
             var metadataProvider = new EmptyModelMetadataProvider();
             var htmlGenerator = new TestableHtmlGenerator(metadataProvider);
@@ -169,7 +174,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             // Assert
             Assert.Equal(
                 expectedOutput,
-                output.GenerateStartTag() + output.GenerateContent() + output.GenerateEndTag());
+                output.GenerateStartTag() +
+                (output.GenerateContent() as TagHelperContent).GetContent() +
+                output.GenerateEndTag());
         }
 
         [Theory]
@@ -200,14 +207,19 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 contextAttributes,
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult(originalContent));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent(originalContent);
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var output = new TagHelperOutput(originalTagName, originalAttributes, new HtmlEncoder())
             {
-                PreContent = originalPreContent,
-                Content = originalContent,
-                PostContent = originalPostContent,
                 SelfClosing = false,
             };
+            output.PreContent.SetContent(originalPreContent);
+            output.Content.SetContent(originalContent);
+            output.PostContent.SetContent(originalPostContent);
 
             var metadataProvider = new EmptyModelMetadataProvider();
             var htmlGenerator = new TestableHtmlGenerator(metadataProvider);
@@ -256,14 +268,19 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 contextAttributes,
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult(originalContent));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent(originalContent);
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var output = new TagHelperOutput(originalTagName, originalAttributes, new HtmlEncoder())
             {
-                PreContent = originalPreContent,
-                Content = originalContent,
-                PostContent = originalPostContent,
                 SelfClosing = false,
             };
+            output.PreContent.SetContent(originalPreContent);
+            output.Content.SetContent(originalContent);
+            output.PostContent.SetContent(originalPostContent);
 
             var tagHelper = new OptionTagHelper
             {
diff --git a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/ScriptTagHelperTest.cs b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/ScriptTagHelperTest.cs
index ac6512e00d..31e6e2dc78 100644
--- a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/ScriptTagHelperTest.cs
+++ b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/ScriptTagHelperTest.cs
@@ -133,8 +133,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
 
             // Assert
             Assert.Null(output.TagName);
-            Assert.NotNull(output.Content);
-            Assert.True(output.ContentSet);
+            Assert.True(output.IsContentModified);
             Assert.Empty(logger.Logged);
         }
 
@@ -223,7 +222,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
 
             // Assert
             Assert.NotNull(output.TagName);
-            Assert.False(output.ContentSet);
+            Assert.False(output.IsContentModified);
         }
 
         [Theory]
@@ -251,7 +250,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
 
             // Assert
             Assert.Equal("script", output.TagName);
-            Assert.False(output.ContentSet);
+            Assert.False(output.IsContentModified);
 
             Assert.Equal(2, logger.Logged.Count);
 
@@ -286,7 +285,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
 
             // Assert
             Assert.Equal("script", output.TagName);
-            Assert.False(output.ContentSet);
+            Assert.False(output.IsContentModified);
         }
 
         [Fact]
@@ -309,7 +308,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
 
             // Assert
             Assert.Equal("script", output.TagName);
-            Assert.False(output.ContentSet);
+            Assert.False(output.IsContentModified);
 
             Assert.Single(logger.Logged);
 
@@ -360,7 +359,8 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             await helper.ProcessAsync(tagHelperContext, output);
 
             // Assert
-            Assert.StartsWith("<script data-extra=\"something\" src=\"/blank.js\" data-more=\"else\"", output.Content);
+            Assert.StartsWith(
+                "<script data-extra=\"something\" src=\"/blank.js\" data-more=\"else\"", output.Content.GetContent());
             Assert.Empty(logger.Logged);
         }
 
@@ -398,7 +398,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             await helper.ProcessAsync(context, output);
 
             // Assert
-            Assert.Equal("<script src=\"/js/site.js\"></script><script src=\"/common.js\"></script>", output.Content);
+            Assert.Equal("<script src=\"/js/site.js\"></script><script src=\"/common.js\"></script>", output.Content.GetContent());
         }
 
         [Fact]
@@ -436,7 +436,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
 
             // Assert
             Assert.Equal("<script src=\"HtmlEncode[[/js/site.js]]\"></script>" +
-                "<script src=\"HtmlEncode[[/common.js]]\"></script>", output.Content);
+                "<script src=\"HtmlEncode[[/common.js]]\"></script>", output.Content.GetContent());
         }
 
         private TagHelperContext MakeTagHelperContext(
@@ -449,7 +449,12 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 attributes,
                 items: new Dictionary<object, object>(),
                 uniqueId: Guid.NewGuid().ToString("N"),
-                getChildContentAsync: () => Task.FromResult(content));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent(content);
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
         }
 
         private static ViewContext MakeViewContext()
diff --git a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/SelectTagHelperTest.cs b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/SelectTagHelperTest.cs
index bcfd5bbd55..92cc3da776 100644
--- a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/SelectTagHelperTest.cs
+++ b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/SelectTagHelperTest.cs
@@ -202,14 +202,19 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 allAttributes: new Dictionary<string, object>(),
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var output = new TagHelperOutput(expectedTagName, originalAttributes, new HtmlEncoder())
             {
-                PreContent = expectedPreContent,
-                Content = expectedContent,
-                PostContent = originalPostContent,
                 SelfClosing = true,
             };
+            output.PreContent.SetContent(expectedPreContent);
+            output.Content.SetContent(expectedContent);
+            output.PostContent.SetContent(originalPostContent);
 
             var htmlGenerator = new TestableHtmlGenerator(metadataProvider)
             {
@@ -232,9 +237,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             // Assert
             Assert.True(output.SelfClosing);
             Assert.Equal(expectedAttributes, output.Attributes);
-            Assert.Equal(expectedPreContent, output.PreContent);
-            Assert.Equal(expectedContent, output.Content);
-            Assert.Equal(expectedPostContent, output.PostContent);
+            Assert.Equal(expectedPreContent, output.PreContent.GetContent());
+            Assert.Equal(expectedContent, output.Content.GetContent());
+            Assert.Equal(expectedPostContent, output.PostContent.GetContent());
             Assert.Equal(expectedTagName, output.TagName);
 
             Assert.NotNull(viewContext.FormContext?.FormData);
@@ -287,14 +292,19 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 allAttributes: new Dictionary<string, object>(),
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var output = new TagHelperOutput(expectedTagName, originalAttributes, new HtmlEncoder())
             {
-                PreContent = expectedPreContent,
-                Content = expectedContent,
-                PostContent = originalPostContent,
                 SelfClosing = true,
             };
+            output.PreContent.SetContent(expectedPreContent);
+            output.Content.SetContent(expectedContent);
+            output.PostContent.SetContent(originalPostContent);
 
             var htmlGenerator = new TestableHtmlGenerator(metadataProvider)
             {
@@ -325,9 +335,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             // Assert
             Assert.True(output.SelfClosing);
             Assert.Equal(expectedAttributes, output.Attributes);
-            Assert.Equal(expectedPreContent, output.PreContent);
-            Assert.Equal(expectedContent, output.Content);
-            Assert.Equal(expectedPostContent, output.PostContent);
+            Assert.Equal(expectedPreContent, output.PreContent.GetContent());
+            Assert.Equal(expectedContent, output.Content.GetContent());
+            Assert.Equal(expectedPostContent, output.PostContent.GetContent());
             Assert.Equal(expectedTagName, output.TagName);
 
             Assert.NotNull(viewContext.FormContext?.FormData);
@@ -386,14 +396,19 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 allAttributes: new Dictionary<string, object>(),
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var output = new TagHelperOutput(expectedTagName, originalAttributes, new HtmlEncoder())
             {
-                PreContent = expectedPreContent,
-                Content = expectedContent,
-                PostContent = originalPostContent,
-                SelfClosing = true,
+                SelfClosing = true
             };
+            output.PreContent.SetContent(expectedPreContent);
+            output.Content.SetContent(expectedContent);
+            output.PostContent.SetContent(originalPostContent);
 
             var htmlGenerator = new TestableHtmlGenerator(metadataProvider)
             {
@@ -425,9 +440,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             // Assert
             Assert.True(output.SelfClosing);
             Assert.Equal(expectedAttributes, output.Attributes);
-            Assert.Equal(expectedPreContent, output.PreContent);
-            Assert.Equal(expectedContent, output.Content);
-            Assert.Equal(expectedPostContent, output.PostContent);
+            Assert.Equal(expectedPreContent, output.PreContent.GetContent());
+            Assert.Equal(expectedContent, output.Content.GetContent());
+            Assert.Equal(expectedPostContent, output.PostContent.GetContent());
             Assert.Equal(expectedTagName, output.TagName);
 
             Assert.NotNull(viewContext.FormContext?.FormData);
@@ -470,9 +485,14 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 contextAttributes,
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
-            var output = new TagHelperOutput(expectedTagName, originalAttributes, new HtmlEncoder());
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
 
+            var output = new TagHelperOutput(expectedTagName, originalAttributes, new HtmlEncoder());
             var metadataProvider = new EmptyModelMetadataProvider();
             string model = null;
             var modelExplorer = metadataProvider.GetModelExplorerForType(typeof(string), model);
@@ -536,9 +556,13 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 contextAttributes,
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var output = new TagHelperOutput(tagName, originalAttributes, new HtmlEncoder());
-
             var metadataProvider = new EmptyModelMetadataProvider();
             var modelExplorer = metadataProvider.GetModelExplorerForType(modelType, model);
             var modelExpression = new ModelExpression(propertyName, modelExplorer);
@@ -592,7 +616,12 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 contextAttributes,
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var output = new TagHelperOutput(expectedTagName, originalAttributes, new HtmlEncoder());
             var tagHelper = new SelectTagHelper
             {
diff --git a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/TagHelperOutputExtensionsTest.cs b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/TagHelperOutputExtensionsTest.cs
index 52b5c0ab74..f2bc557e39 100644
--- a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/TagHelperOutputExtensionsTest.cs
+++ b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/TagHelperOutputExtensionsTest.cs
@@ -30,7 +30,12 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 },
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.Append("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var expectedAttribute = new KeyValuePair<string, string>(attributeName, attributeValue);
 
             // Act
@@ -61,7 +66,12 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 },
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.Append("Something Else");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
 
             // Act
             tagHelperOutput.CopyHtmlAttribute(attributeName, tagHelperContext);
diff --git a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/TextAreaTagHelperTest.cs b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/TextAreaTagHelperTest.cs
index 6b54a85f94..b38dfd9634 100644
--- a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/TextAreaTagHelperTest.cs
+++ b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/TextAreaTagHelperTest.cs
@@ -117,16 +117,21 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 allAttributes: new Dictionary<string, object>(),
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var htmlAttributes = new Dictionary<string, string>
             {
                 { "class", "form-control" },
             };
             var output = new TagHelperOutput(expectedTagName, htmlAttributes, new HtmlEncoder())
             {
-                Content = "original content",
                 SelfClosing = true,
             };
+            output.Content.SetContent("original content");
 
             var htmlGenerator = new TestableHtmlGenerator(metadataProvider)
             {
@@ -145,7 +150,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             // Assert
             Assert.True(output.SelfClosing);
             Assert.Equal(expectedAttributes, output.Attributes);
-            Assert.Equal(expectedContent, output.Content);
+            Assert.Equal(expectedContent, output.Content.GetContent());
             Assert.Equal(expectedTagName, output.TagName);
         }
 
@@ -174,14 +179,19 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 allAttributes: new Dictionary<string, object>(),
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var output = new TagHelperOutput(expectedTagName, expectedAttributes, new HtmlEncoder())
             {
-                PreContent = expectedPreContent,
-                Content = expectedContent,
-                PostContent = expectedPostContent,
                 SelfClosing = true,
             };
+            output.PreContent.SetContent(expectedPreContent);
+            output.Content.SetContent(expectedContent);
+            output.PostContent.SetContent(expectedPostContent);
 
             var htmlGenerator = new TestableHtmlGenerator(metadataProvider)
             {
@@ -200,7 +210,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
 
             // Assert
             Assert.Equal(expectedAttributes, output.Attributes);
-            Assert.Equal(expectedContent, output.Content);
+            Assert.Equal(expectedContent, output.Content.GetContent());
             Assert.True(output.SelfClosing);
             Assert.Equal(expectedTagName, output.TagName);
         }
diff --git a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/ValidationMessageTagHelperTest.cs b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/ValidationMessageTagHelperTest.cs
index 3f9450028a..4d899b4b90 100644
--- a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/ValidationMessageTagHelperTest.cs
+++ b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/ValidationMessageTagHelperTest.cs
@@ -41,19 +41,22 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 },
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var output = new TagHelperOutput(
                 expectedTagName,
                 attributes: new Dictionary<string, string>
                 {
                     { "id", "myvalidationmessage" }
                 },
-                htmlEncoder: new HtmlEncoder())
-            {
-                PreContent = expectedPreContent,
-                Content = expectedContent,
-                PostContent = expectedPostContent,
-            };
+                htmlEncoder: new HtmlEncoder());
+            output.PreContent.SetContent(expectedPreContent);
+            output.Content.SetContent(expectedContent);
+            output.PostContent.SetContent(expectedPostContent);
             var htmlGenerator = new TestableHtmlGenerator(metadataProvider);
             var viewContext = TestableHtmlGenerator.GetViewContext(model: null,
                                                                    htmlGenerator: htmlGenerator,
@@ -74,9 +77,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             Assert.Equal("Name", attribute.Value);
             attribute = Assert.Single(output.Attributes, kvp => kvp.Key.Equals("data-valmsg-replace"));
             Assert.Equal("true", attribute.Value);
-            Assert.Equal(expectedPreContent, output.PreContent);
-            Assert.Equal(expectedContent, output.Content);
-            Assert.Equal(expectedPostContent, output.PostContent);
+            Assert.Equal(expectedPreContent, output.PreContent.GetContent());
+            Assert.Equal(expectedContent, output.Content.GetContent());
+            Assert.Equal(expectedPostContent, output.PostContent.GetContent());
             Assert.Equal(expectedTagName, output.TagName);
         }
 
@@ -95,16 +98,20 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 allAttributes: new Dictionary<string, object>(),
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var output = new TagHelperOutput(
                 "span",
                 attributes: new Dictionary<string, string>(),
-                htmlEncoder: new HtmlEncoder())
-            {
-                PreContent = expectedPreContent,
-                Content = expectedContent,
-                PostContent = expectedPostContent,
-            };
+                htmlEncoder: new HtmlEncoder());
+            output.PreContent.SetContent(expectedPreContent);
+            output.Content.SetContent(expectedContent);
+            output.PostContent.SetContent(expectedPostContent);
+
             var expectedViewContext = CreateViewContext();
             var generator = new Mock<IHtmlGenerator>();
             generator
@@ -121,9 +128,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             generator.Verify();
             Assert.Equal("span", output.TagName);
             Assert.Empty(output.Attributes);
-            Assert.Equal(expectedPreContent, output.PreContent);
-            Assert.Equal(expectedContent, output.Content);
-            Assert.Equal(expectedPostContent, output.PostContent);
+            Assert.Equal(expectedPreContent, output.PreContent.GetContent());
+            Assert.Equal(expectedContent, output.Content.GetContent());
+            Assert.Equal(expectedPostContent, output.PostContent.GetContent());
         }
 
         [Theory]
@@ -141,16 +148,19 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             var output = new TagHelperOutput(
                 "span",
                 attributes: new Dictionary<string, string>(),
-                htmlEncoder: new HtmlEncoder())
-            {
-                Content = outputContent
-            };
+                htmlEncoder: new HtmlEncoder());
+            output.Content.SetContent(outputContent);
 
             var context = new TagHelperContext(
                 allAttributes: new Dictionary<string, object>(),
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult(childContent));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent(childContent);
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var tagBuilder = new TagBuilder("span2", new HtmlEncoder())
             {
                 InnerHtml = "New HTML"
@@ -181,7 +191,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             Assert.Equal("bar", attribute.Value);
             attribute = Assert.Single(output.Attributes, kvp => kvp.Key.Equals("data-hello"));
             Assert.Equal("world", attribute.Value);
-            Assert.Equal(expectedOutputContent, output.Content);
+            Assert.Equal(expectedOutputContent, output.Content.GetContent());
         }
 
         [Theory]
@@ -204,7 +214,12 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 allAttributes: new Dictionary<string, object>(),
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult(childContent));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent(childContent);
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var tagBuilder = new TagBuilder("span2", new HtmlEncoder())
             {
                 InnerHtml = "New HTML"
@@ -235,7 +250,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             Assert.Equal("bar", attribute.Value);
             attribute = Assert.Single(output.Attributes, kvp => kvp.Key.Equals("data-hello"));
             Assert.Equal("world", attribute.Value);
-            Assert.Equal(expectedOutputContent, output.Content);
+            Assert.Equal(expectedOutputContent, output.Content.GetContent());
         }
 
         [Fact]
@@ -249,12 +264,11 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             var output = new TagHelperOutput(
                 "span",
                 attributes: new Dictionary<string, string>(),
-                htmlEncoder: new HtmlEncoder())
-            {
-                PreContent = expectedPreContent,
-                Content = expectedContent,
-                PostContent = expectedPostContent,
-            };
+                htmlEncoder: new HtmlEncoder());
+            output.PreContent.SetContent(expectedPreContent);
+            output.Content.SetContent(expectedContent);
+            output.PostContent.SetContent(expectedPostContent);
+
             var viewContext = CreateViewContext();
             var generator = new Mock<IHtmlGenerator>(MockBehavior.Strict);
             validationMessageTagHelper.ViewContext = viewContext;
@@ -266,9 +280,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             // Assert
             Assert.Equal("span", output.TagName);
             Assert.Empty(output.Attributes);
-            Assert.Equal(expectedPreContent, output.PreContent);
-            Assert.Equal(expectedContent, output.Content);
-            Assert.Equal(expectedPostContent, output.PostContent);
+            Assert.Equal(expectedPreContent, output.PreContent.GetContent());
+            Assert.Equal(expectedContent, output.Content.GetContent());
+            Assert.Equal(expectedPostContent, output.PostContent.GetContent());
         }
 
         private static ModelExpression CreateModelExpression(string name)
diff --git a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/ValidationSummaryTagHelperTest.cs b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/ValidationSummaryTagHelperTest.cs
index 6f38ddf41a..50e8c3aa96 100644
--- a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/ValidationSummaryTagHelperTest.cs
+++ b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/ValidationSummaryTagHelperTest.cs
@@ -47,19 +47,22 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 allAttributes: new Dictionary<string, object>(),
                 items: new Dictionary<object, object>(),
                 uniqueId: "test",
-                getChildContentAsync: () => Task.FromResult("Something"));
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
             var output = new TagHelperOutput(
                 expectedTagName,
                 attributes: new Dictionary<string, string>
                 {
                     { "class", "form-control" }
                 },
-                htmlEncoder: new HtmlEncoder())
-            {
-                PreContent = expectedPreContent,
-                Content = expectedContent,
-                PostContent = "Custom Content",
-            };
+                htmlEncoder: new HtmlEncoder());
+            output.PreContent.SetContent(expectedPreContent);
+            output.Content.SetContent(expectedContent);
+            output.PostContent.SetContent("Custom Content");
 
             var htmlGenerator = new TestableHtmlGenerator(metadataProvider);
             Model model = null;
@@ -76,10 +79,10 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             Assert.Equal("form-control validation-summary-valid", attribute.Value);
             attribute = Assert.Single(output.Attributes, kvp => kvp.Key.Equals("data-valmsg-summary"));
             Assert.Equal("true", attribute.Value);
-            Assert.Equal(expectedPreContent, output.PreContent);
-            Assert.Equal(expectedContent, output.Content);
+            Assert.Equal(expectedPreContent, output.PreContent.GetContent());
+            Assert.Equal(expectedContent, output.Content.GetContent());
             Assert.Equal("Custom Content<ul><li style=\"display:none\"></li>" + Environment.NewLine + "</ul>",
-                         output.PostContent);
+                         output.PostContent.GetContent());
             Assert.Equal(expectedTagName, output.TagName);
         }
 
@@ -101,12 +104,11 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             var output = new TagHelperOutput(
                 "div",
                 attributes: new Dictionary<string, string>(),
-                htmlEncoder: new HtmlEncoder())
-            {
-                PreContent = expectedPreContent,
-                Content = expectedContent,
-                PostContent = expectedPostContent,
-            };
+                htmlEncoder: new HtmlEncoder());
+            output.PreContent.SetContent(expectedPreContent);
+            output.Content.SetContent(expectedContent);
+            output.PostContent.SetContent(expectedPostContent);
+
             var expectedViewContext = CreateViewContext();
             var generator = new Mock<IHtmlGenerator>();
             generator
@@ -127,9 +129,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             generator.Verify();
             Assert.Equal("div", output.TagName);
             Assert.Empty(output.Attributes);
-            Assert.Equal(expectedPreContent, output.PreContent);
-            Assert.Equal(expectedContent, output.Content);
-            Assert.Equal(expectedPostContent, output.PostContent);
+            Assert.Equal(expectedPreContent, output.PreContent.GetContent());
+            Assert.Equal(expectedContent, output.Content.GetContent());
+            Assert.Equal(expectedPostContent, output.PostContent.GetContent());
         }
 
         [Fact]
@@ -145,12 +147,11 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             var output = new TagHelperOutput(
                 "div",
                 attributes: new Dictionary<string, string>(),
-                htmlEncoder: new HtmlEncoder())
-            {
-                PreContent = expectedPreContent,
-                Content = expectedContent,
-                PostContent = "Content of validation summary"
-            };
+                htmlEncoder: new HtmlEncoder());
+            output.PreContent.SetContent(expectedPreContent);
+            output.Content.SetContent(expectedContent);
+            output.PostContent.SetContent("Content of validation summary");
+
             var tagBuilder = new TagBuilder("span2", new HtmlEncoder())
             {
                 InnerHtml = "New HTML"
@@ -185,9 +186,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             Assert.Equal("world", attribute.Value);
             attribute = Assert.Single(output.Attributes, kvp => kvp.Key.Equals("anything"));
             Assert.Equal("something", attribute.Value);
-            Assert.Equal(expectedPreContent, output.PreContent);
-            Assert.Equal(expectedContent, output.Content);
-            Assert.Equal("Content of validation summaryNew HTML", output.PostContent);
+            Assert.Equal(expectedPreContent, output.PreContent.GetContent());
+            Assert.Equal(expectedContent, output.Content.GetContent());
+            Assert.Equal("Content of validation summaryNew HTML", output.PostContent.GetContent());
         }
 
         [Fact]
@@ -204,12 +205,10 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             var output = new TagHelperOutput(
                 "div",
                 attributes: new Dictionary<string, string>(),
-                htmlEncoder: new HtmlEncoder())
-            {
-                PreContent = expectedPreContent,
-                Content = expectedContent,
-                PostContent = expectedPostContent,
-            };
+                htmlEncoder: new HtmlEncoder());
+            output.PreContent.SetContent(expectedPreContent);
+            output.Content.SetContent(expectedContent);
+            output.PostContent.SetContent(expectedPostContent);
 
             var generator = new Mock<IHtmlGenerator>(MockBehavior.Strict);
             var viewContext = CreateViewContext();
@@ -222,9 +221,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             // Assert
             Assert.Equal("div", output.TagName);
             Assert.Empty(output.Attributes);
-            Assert.Equal(expectedPreContent, output.PreContent);
-            Assert.Equal(expectedContent, output.Content);
-            Assert.Equal(expectedPostContent, output.PostContent);
+            Assert.Equal(expectedPreContent, output.PreContent.GetContent());
+            Assert.Equal(expectedContent, output.Content.GetContent());
+            Assert.Equal(expectedPostContent, output.PostContent.GetContent());
         }
 
         [Theory]
@@ -242,12 +241,10 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             var output = new TagHelperOutput(
                 "div",
                 attributes: new Dictionary<string, string>(),
-                htmlEncoder: new HtmlEncoder())
-            {
-                PreContent = expectedPreContent,
-                Content = expectedContent,
-                PostContent = "Content of validation message",
-            };
+                htmlEncoder: new HtmlEncoder());
+            output.PreContent.SetContent(expectedPreContent);
+            output.Content.SetContent(expectedContent);
+            output.PostContent.SetContent("Content of validation message");
             var tagBuilder = new TagBuilder("span2", new HtmlEncoder())
             {
                 InnerHtml = "New HTML"
@@ -273,9 +270,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             // Assert
             Assert.Equal("div", output.TagName);
             Assert.Empty(output.Attributes);
-            Assert.Equal(expectedPreContent, output.PreContent);
-            Assert.Equal(expectedContent, output.Content);
-            Assert.Equal("Content of validation messageNew HTML", output.PostContent);
+            Assert.Equal(expectedPreContent, output.PreContent.GetContent());
+            Assert.Equal(expectedContent, output.Content.GetContent());
+            Assert.Equal("Content of validation messageNew HTML", output.PostContent.GetContent());
             generator.Verify();
         }
 
diff --git a/test/WebSites/ActivatorWebSite/TagHelpers/FooterTagHelper.cs b/test/WebSites/ActivatorWebSite/TagHelpers/FooterTagHelper.cs
index 4dd643184c..b569297c6e 100644
--- a/test/WebSites/ActivatorWebSite/TagHelpers/FooterTagHelper.cs
+++ b/test/WebSites/ActivatorWebSite/TagHelpers/FooterTagHelper.cs
@@ -18,7 +18,7 @@ namespace ActivatorWebSite.TagHelpers
 
         public override void Process(TagHelperContext context, TagHelperOutput output)
         {
-            output.PostContent = $"<footer>{HtmlHelper.Encode(ViewData["footer"])}</footer>";
+            output.PostContent.SetContent($"<footer>{HtmlHelper.Encode(ViewData["footer"])}</footer>");
         }
     }
 }
\ No newline at end of file
diff --git a/test/WebSites/ActivatorWebSite/TagHelpers/HiddenTagHelper.cs b/test/WebSites/ActivatorWebSite/TagHelpers/HiddenTagHelper.cs
index b031b4a14f..79db55d8fb 100644
--- a/test/WebSites/ActivatorWebSite/TagHelpers/HiddenTagHelper.cs
+++ b/test/WebSites/ActivatorWebSite/TagHelpers/HiddenTagHelper.cs
@@ -20,7 +20,7 @@ namespace ActivatorWebSite.TagHelpers
         {
             var content = await context.GetChildContentAsync();
 
-            output.Content = HtmlHelper.Hidden(Name, content).ToString();
+            output.Content.SetContent(HtmlHelper.Hidden(Name, content).ToString());
         }
     }
 }
\ No newline at end of file
diff --git a/test/WebSites/ActivatorWebSite/TagHelpers/RepeatContentTagHelper.cs b/test/WebSites/ActivatorWebSite/TagHelpers/RepeatContentTagHelper.cs
index 1780100eb4..7b2003150a 100644
--- a/test/WebSites/ActivatorWebSite/TagHelpers/RepeatContentTagHelper.cs
+++ b/test/WebSites/ActivatorWebSite/TagHelpers/RepeatContentTagHelper.cs
@@ -25,12 +25,12 @@ namespace ActivatorWebSite.TagHelpers
 
             if (string.IsNullOrEmpty(repeatContent))
             {
-                repeatContent = content;
+                repeatContent = content.GetContent();
             }
 
             for (int i = 0; i < RepeatContent; i++)
             {
-                output.Content += repeatContent;
+                output.Content.Append(repeatContent);
             }
         }
 
diff --git a/test/WebSites/ActivatorWebSite/TagHelpers/TitleTagHelper.cs b/test/WebSites/ActivatorWebSite/TagHelpers/TitleTagHelper.cs
index 8a99555798..c63d319cd7 100644
--- a/test/WebSites/ActivatorWebSite/TagHelpers/TitleTagHelper.cs
+++ b/test/WebSites/ActivatorWebSite/TagHelpers/TitleTagHelper.cs
@@ -22,7 +22,7 @@ namespace ActivatorWebSite.TagHelpers
             var builder = new TagBuilder("h2", HtmlHelper.HtmlEncoder);
             var title = ViewContext.ViewBag.Title;
             builder.InnerHtml = HtmlHelper.Encode(title);
-            output.PreContent = builder.ToString();
+            output.PreContent.SetContent(builder.ToString());
         }
     }
 }
\ No newline at end of file
diff --git a/test/WebSites/RequestServicesWebSite/RequestScopedTagHelper.cs b/test/WebSites/RequestServicesWebSite/RequestScopedTagHelper.cs
index d0743d66d2..cec089aaf0 100644
--- a/test/WebSites/RequestServicesWebSite/RequestScopedTagHelper.cs
+++ b/test/WebSites/RequestServicesWebSite/RequestScopedTagHelper.cs
@@ -14,7 +14,7 @@ namespace RequestServicesWebSite
 
         public override void Process(TagHelperContext context, TagHelperOutput output)
         {
-            output.Content = RequestIdService.RequestId;
+            output.Content.SetContent(RequestIdService.RequestId);
         }
     }
 }
\ No newline at end of file
diff --git a/test/WebSites/TagHelpersWebSite/TagHelpers/ATagHelper.cs b/test/WebSites/TagHelpersWebSite/TagHelpers/ATagHelper.cs
index 40355cf6b8..6759200744 100644
--- a/test/WebSites/TagHelpersWebSite/TagHelpers/ATagHelper.cs
+++ b/test/WebSites/TagHelpersWebSite/TagHelpers/ATagHelper.cs
@@ -30,7 +30,7 @@ namespace TagHelpersWebSite.TagHelpers
 
                 output.Attributes["href"] = UrlHelper.Action(Action, Controller, methodParameters);
 
-                output.PreContent = "My ";
+                output.PreContent.SetContent("My ");
             }
         }
     }
diff --git a/test/WebSites/TagHelpersWebSite/TagHelpers/AutoLinkerTagHelper.cs b/test/WebSites/TagHelpersWebSite/TagHelpers/AutoLinkerTagHelper.cs
index 71a0111864..62bb8e49c4 100644
--- a/test/WebSites/TagHelpersWebSite/TagHelpers/AutoLinkerTagHelper.cs
+++ b/test/WebSites/TagHelpersWebSite/TagHelpers/AutoLinkerTagHelper.cs
@@ -4,7 +4,6 @@
 using System.Text.RegularExpressions;
 using System.Threading.Tasks;
 using Microsoft.AspNet.Razor.Runtime.TagHelpers;
-using Microsoft.AspNet.Razor.TagHelpers;
 
 namespace TagHelpersWebSite.TagHelpers
 {
@@ -16,10 +15,10 @@ namespace TagHelpersWebSite.TagHelpers
             var childContent = await context.GetChildContentAsync();
 
             // Find Urls in the content and replace them with their anchor tag equivalent.
-            output.Content = Regex.Replace(
-                childContent,
+            output.Content.SetContent(Regex.Replace(
+                childContent.GetContent(),
                 @"\b(?:https?://|www\.)(\S+)\b",
-                "<strong><a target=\"_blank\" href=\"http://$0\">$0</a></strong>");
+                "<strong><a target=\"_blank\" href=\"http://$0\">$0</a></strong>"));
         }
     }
 }
\ No newline at end of file
diff --git a/test/WebSites/TagHelpersWebSite/TagHelpers/NestedViewStartTagHelper.cs b/test/WebSites/TagHelpersWebSite/TagHelpers/NestedViewStartTagHelper.cs
index 8ef3daa358..059df3e4b8 100644
--- a/test/WebSites/TagHelpersWebSite/TagHelpers/NestedViewStartTagHelper.cs
+++ b/test/WebSites/TagHelpersWebSite/TagHelpers/NestedViewStartTagHelper.cs
@@ -11,7 +11,7 @@ namespace TagHelpersWebSite.TagHelpers
     {
         public override void Process(TagHelperContext context, TagHelperOutput output)
         {
-            output.Content = "nested-content";
+            output.Content.SetContent("nested-content");
         }
     }
 }
\ No newline at end of file
diff --git a/test/WebSites/TagHelpersWebSite/TagHelpers/RootViewStartTagHelper.cs b/test/WebSites/TagHelpersWebSite/TagHelpers/RootViewStartTagHelper.cs
index d5d9fa15d0..35459ff842 100644
--- a/test/WebSites/TagHelpersWebSite/TagHelpers/RootViewStartTagHelper.cs
+++ b/test/WebSites/TagHelpersWebSite/TagHelpers/RootViewStartTagHelper.cs
@@ -11,7 +11,7 @@ namespace TagHelpersWebSite.TagHelpers
     {
         public override void Process(TagHelperContext context, TagHelperOutput output)
         {
-            output.Content = "root-content";
+            output.Content.SetContent("root-content");
         }
     }
 }
\ No newline at end of file
diff --git a/test/WebSites/TagHelpersWebSite/TagHelpers/TagCloudViewComponentTagHelper.cs b/test/WebSites/TagHelpersWebSite/TagHelpers/TagCloudViewComponentTagHelper.cs
index 5e4ec503f3..5a9a576a1e 100644
--- a/test/WebSites/TagHelpersWebSite/TagHelpers/TagCloudViewComponentTagHelper.cs
+++ b/test/WebSites/TagHelpersWebSite/TagHelpers/TagCloudViewComponentTagHelper.cs
@@ -8,7 +8,6 @@ using System.Reflection;
 using System.Threading.Tasks;
 using Microsoft.AspNet.Mvc;
 using Microsoft.AspNet.Razor.Runtime.TagHelpers;
-using Microsoft.AspNet.Razor.TagHelpers;
 
 namespace MvcSample.Web.Components
 {
@@ -42,7 +41,7 @@ namespace MvcSample.Web.Components
                                          writer));
 
             output.TagName = null;
-            output.Content = writer.ToString();
+            output.Content.SetContent(writer.ToString());
         }
 
         public async Task<IViewComponentResult> InvokeAsync(int count)
diff --git a/test/WebSites/TagHelpersWebSite/TagHelpers/WebsiteInformationTagHelper.cs b/test/WebSites/TagHelpersWebSite/TagHelpers/WebsiteInformationTagHelper.cs
index dbc5afedf0..90726a7cc6 100644
--- a/test/WebSites/TagHelpersWebSite/TagHelpers/WebsiteInformationTagHelper.cs
+++ b/test/WebSites/TagHelpersWebSite/TagHelpers/WebsiteInformationTagHelper.cs
@@ -14,7 +14,7 @@ namespace TagHelpersWebSite.TagHelpers
         public override void Process(TagHelperContext context, TagHelperOutput output)
         {
             output.TagName = "section";
-            output.PostContent = string.Format(
+            output.PostContent.SetContent(string.Format(
                 "<p><strong>Version:</strong> {0}</p>" + Environment.NewLine +
                 "<p><strong>Copyright Year:</strong> {1}</p>" + Environment.NewLine +
                 "<p><strong>Approved:</strong> {2}</p>" + Environment.NewLine +
@@ -22,7 +22,7 @@ namespace TagHelpersWebSite.TagHelpers
                 Info.Version.ToString(),
                 Info.CopyrightYear.ToString(),
                 Info.Approved.ToString(),
-                Info.TagsToShow.ToString());
+                Info.TagsToShow.ToString()));
             output.SelfClosing = false;
         }
     }