#361 Introduce StringValues to replace string[] usage.

HttpAbstractions.sln

@@ -1,7 +1,7 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio 14
-VisualStudioVersion = 14.0.22823.1
+VisualStudioVersion = 14.0.23107.0
 MinimumVisualStudioVersion = 10.0.40219.1
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "src", "src", "{A5A15F1C-885A-452A-A731-B0173DDBD913}"
 EndProject
@@ -43,6 +43,14 @@ Project("{8BB2217D-0F2D-49D1-97BC-3654ED321F3B}") = "Microsoft.Framework.WebEnco
 EndProject
 Project("{8BB2217D-0F2D-49D1-97BC-3654ED321F3B}") = "Microsoft.AspNet.Html.Abstractions", "src\Microsoft.AspNet.Html.Abstractions\Microsoft.AspNet.Html.Abstractions.xproj", "{68A28E4A-3ADE-4187-9625-4FF185887CB3}"
 EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "samples", "samples", "{982F09D8-621E-4872-BA7B-BBDEA47D1EFD}"
+EndProject
+Project("{8BB2217D-0F2D-49D1-97BC-3654ED321F3B}") = "SampleApp", "samples\SampleApp\SampleApp.xproj", "{1D0764B4-1DEB-4232-A714-D4B7E846918A}"
+EndProject
+Project("{8BB2217D-0F2D-49D1-97BC-3654ED321F3B}") = "Microsoft.Framework.Primitives", "src\Microsoft.Framework.Primitives\Microsoft.Framework.Primitives.xproj", "{E5FACCD4-6327-43AA-80A9-AE6F4A3BFE6A}"
+EndProject
+Project("{8BB2217D-0F2D-49D1-97BC-3654ED321F3B}") = "Microsoft.Framework.Primitives.Tests", "test\Microsoft.Framework.Primitives.Tests\Microsoft.Framework.Primitives.Tests.xproj", "{61F72E92-B3AE-4A10-B838-44F80AED40AE}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -245,6 +253,42 @@ Global
 		{68A28E4A-3ADE-4187-9625-4FF185887CB3}.Release|Mixed Platforms.Build.0 = Release|Any CPU
 		{68A28E4A-3ADE-4187-9625-4FF185887CB3}.Release|x86.ActiveCfg = Release|Any CPU
 		{68A28E4A-3ADE-4187-9625-4FF185887CB3}.Release|x86.Build.0 = Release|Any CPU
+		{1D0764B4-1DEB-4232-A714-D4B7E846918A}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{1D0764B4-1DEB-4232-A714-D4B7E846918A}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{1D0764B4-1DEB-4232-A714-D4B7E846918A}.Debug|Mixed Platforms.ActiveCfg = Debug|Any CPU
+		{1D0764B4-1DEB-4232-A714-D4B7E846918A}.Debug|Mixed Platforms.Build.0 = Debug|Any CPU
+		{1D0764B4-1DEB-4232-A714-D4B7E846918A}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{1D0764B4-1DEB-4232-A714-D4B7E846918A}.Debug|x86.Build.0 = Debug|Any CPU
+		{1D0764B4-1DEB-4232-A714-D4B7E846918A}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{1D0764B4-1DEB-4232-A714-D4B7E846918A}.Release|Any CPU.Build.0 = Release|Any CPU
+		{1D0764B4-1DEB-4232-A714-D4B7E846918A}.Release|Mixed Platforms.ActiveCfg = Release|Any CPU
+		{1D0764B4-1DEB-4232-A714-D4B7E846918A}.Release|Mixed Platforms.Build.0 = Release|Any CPU
+		{1D0764B4-1DEB-4232-A714-D4B7E846918A}.Release|x86.ActiveCfg = Release|Any CPU
+		{1D0764B4-1DEB-4232-A714-D4B7E846918A}.Release|x86.Build.0 = Release|Any CPU
+		{E5FACCD4-6327-43AA-80A9-AE6F4A3BFE6A}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{E5FACCD4-6327-43AA-80A9-AE6F4A3BFE6A}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{E5FACCD4-6327-43AA-80A9-AE6F4A3BFE6A}.Debug|Mixed Platforms.ActiveCfg = Debug|Any CPU
+		{E5FACCD4-6327-43AA-80A9-AE6F4A3BFE6A}.Debug|Mixed Platforms.Build.0 = Debug|Any CPU
+		{E5FACCD4-6327-43AA-80A9-AE6F4A3BFE6A}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{E5FACCD4-6327-43AA-80A9-AE6F4A3BFE6A}.Debug|x86.Build.0 = Debug|Any CPU
+		{E5FACCD4-6327-43AA-80A9-AE6F4A3BFE6A}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{E5FACCD4-6327-43AA-80A9-AE6F4A3BFE6A}.Release|Any CPU.Build.0 = Release|Any CPU
+		{E5FACCD4-6327-43AA-80A9-AE6F4A3BFE6A}.Release|Mixed Platforms.ActiveCfg = Release|Any CPU
+		{E5FACCD4-6327-43AA-80A9-AE6F4A3BFE6A}.Release|Mixed Platforms.Build.0 = Release|Any CPU
+		{E5FACCD4-6327-43AA-80A9-AE6F4A3BFE6A}.Release|x86.ActiveCfg = Release|Any CPU
+		{E5FACCD4-6327-43AA-80A9-AE6F4A3BFE6A}.Release|x86.Build.0 = Release|Any CPU
+		{61F72E92-B3AE-4A10-B838-44F80AED40AE}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{61F72E92-B3AE-4A10-B838-44F80AED40AE}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{61F72E92-B3AE-4A10-B838-44F80AED40AE}.Debug|Mixed Platforms.ActiveCfg = Debug|Any CPU
+		{61F72E92-B3AE-4A10-B838-44F80AED40AE}.Debug|Mixed Platforms.Build.0 = Debug|Any CPU
+		{61F72E92-B3AE-4A10-B838-44F80AED40AE}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{61F72E92-B3AE-4A10-B838-44F80AED40AE}.Debug|x86.Build.0 = Debug|Any CPU
+		{61F72E92-B3AE-4A10-B838-44F80AED40AE}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{61F72E92-B3AE-4A10-B838-44F80AED40AE}.Release|Any CPU.Build.0 = Release|Any CPU
+		{61F72E92-B3AE-4A10-B838-44F80AED40AE}.Release|Mixed Platforms.ActiveCfg = Release|Any CPU
+		{61F72E92-B3AE-4A10-B838-44F80AED40AE}.Release|Mixed Platforms.Build.0 = Release|Any CPU
+		{61F72E92-B3AE-4A10-B838-44F80AED40AE}.Release|x86.ActiveCfg = Release|Any CPU
+		{61F72E92-B3AE-4A10-B838-44F80AED40AE}.Release|x86.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -268,5 +312,8 @@ Global
 		{7AE2731D-43CD-4CF8-850A-4914DE2CE930} = {F31FF137-390C-49BF-A3BD-7C6ED3597C21}
 		{BE9112CB-D87D-4080-9CC3-24492D49CBE6} = {A5A15F1C-885A-452A-A731-B0173DDBD913}
 		{68A28E4A-3ADE-4187-9625-4FF185887CB3} = {A5A15F1C-885A-452A-A731-B0173DDBD913}
+		{1D0764B4-1DEB-4232-A714-D4B7E846918A} = {982F09D8-621E-4872-BA7B-BBDEA47D1EFD}
+		{E5FACCD4-6327-43AA-80A9-AE6F4A3BFE6A} = {A5A15F1C-885A-452A-A731-B0173DDBD913}
+		{61F72E92-B3AE-4A10-B838-44F80AED40AE} = {F31FF137-390C-49BF-A3BD-7C6ED3597C21}
 	EndGlobalSection
 EndGlobal

samples/SampleApp/Program.cs

@@ -0,0 +1,30 @@
+using System;
+using System.Diagnostics;
+using Microsoft.Framework.Primitives;
+
+namespace SampleApp
+{
+    public class Program
+    {
+        public void Main(string[] args)
+        {
+            for (int i = 0; i < 10; i++)
+            {
+                Stopwatch timer = new Stopwatch();
+                timer.Start();
+                string myString;
+                string[] myArray;
+                StringValues myValues;
+                for (int j = 0; j < 100000000; j++)
+                {
+                    myString = new string('a', 40);
+                    myArray = new[] { myString };
+                    // myValues = new StringValues(myString);
+                    myValues = new StringValues(myArray);
+                }
+                timer.Stop();
+                Console.WriteLine(timer.Elapsed + ", " + Environment.WorkingSet);
+            }
+        }
+    }
+}

samples/SampleApp/SampleApp.xproj

@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="14.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <PropertyGroup>
+    <VisualStudioVersion Condition="'$(VisualStudioVersion)' == ''">14.0</VisualStudioVersion>
+    <VSToolsPath Condition="'$(VSToolsPath)' == ''">$(MSBuildExtensionsPath32)\Microsoft\VisualStudio\v$(VisualStudioVersion)</VSToolsPath>
+  </PropertyGroup>
+
+  <Import Project="$(VSToolsPath)\DNX\Microsoft.DNX.Props" Condition="'$(VSToolsPath)' != ''" />
+  <PropertyGroup Label="Globals">
+    <ProjectGuid>1d0764b4-1deb-4232-a714-d4b7e846918a</ProjectGuid>
+    <RootNamespace>SampleApp</RootNamespace>
+    <BaseIntermediateOutputPath Condition="'$(BaseIntermediateOutputPath)'=='' ">..\..\artifacts\obj\$(MSBuildProjectName)</BaseIntermediateOutputPath>
+    <OutputPath Condition="'$(OutputPath)'=='' ">..\..\artifacts\bin\$(MSBuildProjectName)\</OutputPath>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <SchemaVersion>2.0</SchemaVersion>
+  </PropertyGroup>
+  <Import Project="$(VSToolsPath)\DNX\Microsoft.DNX.targets" Condition="'$(VSToolsPath)' != ''" />
+</Project>

samples/SampleApp/project.json

@@ -0,0 +1,15 @@
+{
+  "version": "1.0.0-*",
+
+  "dependencies": {
+    "Microsoft.AspNet.Http": "1.0.0-*"
+  },
+
+  "commands": {
+    "SampleApp": "SampleApp"
+  },
+
+  "frameworks": {
+    "dnx451": { }
+  }
+}

src/Microsoft.AspNet.Http.Abstractions/IHeaderDictionary.cs

@@ -2,29 +2,30 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System.Collections.Generic;
-using System.Diagnostics.CodeAnalysis;
+using Microsoft.Framework.Primitives;
 
 namespace Microsoft.AspNet.Http
 {
     /// <summary>
     /// Represents request and response headers
     /// </summary>
-    public interface IHeaderDictionary : IReadableStringCollection, IDictionary<string, string[]>
+    public interface IHeaderDictionary : IReadableStringCollection, IDictionary<string, StringValues>
     {
+        // This property is duplicated to resolve an ambiguity between IReadableStringCollection and IDictionary<string, StringValues>
         /// <summary>
-        /// Get or sets the associated value from the collection as a single string.
+        ///
         /// </summary>
-        /// <param name="key">The header name.</param>
+        /// <param name="key"></param>
-        /// <returns>the associated value from the collection as a single string or null if the key is not present.</returns>
+        /// <returns>The stored value, or StringValues.Empty if the key is not present.</returns>
-        new string this[string key] { get; set; }
+        new StringValues this[string key] { get; set; }
 
-        // This property is duplicated to resolve an ambiguity between IReadableStringCollection.Count and IDictionary<string, string[]>.Count
+        // This property is duplicated to resolve an ambiguity between IReadableStringCollection.Count and IDictionary<string, StringValues>.Count
         /// <summary>
         /// Gets the number of elements contained in the collection.
         /// </summary>
         new int Count { get; }
 
-        // This property is duplicated to resolve an ambiguity between IReadableStringCollection.Keys and IDictionary<string, string[]>.Keys
+        // This property is duplicated to resolve an ambiguity between IReadableStringCollection.Keys and IDictionary<string, StringValues>.Keys
         /// <summary>
         /// Gets a collection containing the keys.
         /// </summary>
@@ -36,21 +37,14 @@ namespace Microsoft.AspNet.Http
         /// </summary>
         /// <param name="key">The header name.</param>
         /// <returns>the associated values from the collection separated into individual values, or null if the key is not present.</returns>
-        IList<string> GetCommaSeparatedValues(string key);
+        StringValues GetCommaSeparatedValues(string key);
 
         /// <summary>
-        /// Add a new value. Appends to the header if already present
+        /// Add a new value. Appends to the header list if already present
         /// </summary>
         /// <param name="key">The header name.</param>
         /// <param name="value">The header value.</param>
-        void Append(string key, string value);
+        void Append(string key, StringValues value);
-
-        /// <summary>
-        /// Add new values. Each item remains a separate array entry.
-        /// </summary>
-        /// <param name="key">The header name.</param>
-        /// <param name="values">The header values.</param>
-        void AppendValues(string key, params string[] values);
 
         /// <summary>
         /// Quotes any values containing comas, and then coma joins all of the values with any existing values.
@@ -59,21 +53,6 @@ namespace Microsoft.AspNet.Http
         /// <param name="values">The header values.</param>
         void AppendCommaSeparatedValues(string key, params string[] values);
 
-        /// <summary>
-        /// Sets a specific header value.
-        /// </summary>
-        /// <param name="key">The header name.</param>
-        /// <param name="value">The header value.</param>
-        [SuppressMessage("Microsoft.Naming", "CA1716:IdentifiersShouldNotMatchKeywords", MessageId = "Set", Justification = "Re-evaluate later.")]
-        void Set(string key, string value);
-
-        /// <summary>
-        /// Sets the specified header values without modification.
-        /// </summary>
-        /// <param name="key">The header name.</param>
-        /// <param name="values">The header values.</param>
-        void SetValues(string key, params string[] values);
-
         /// <summary>
         /// Quotes any values containing comas, and then coma joins all of the values.
         /// </summary>

src/Microsoft.AspNet.Http.Abstractions/IReadableStringCollection.cs

@@ -2,22 +2,22 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System.Collections.Generic;
-using System.Diagnostics.CodeAnalysis;
+using Microsoft.Framework.Primitives;
 
 namespace Microsoft.AspNet.Http
 {
     /// <summary>
     /// Accessors for headers, query, forms, etc.
     /// </summary>
-    public interface IReadableStringCollection : IEnumerable<KeyValuePair<string, string[]>>
+    public interface IReadableStringCollection : IEnumerable<KeyValuePair<string, StringValues>>
     {
         /// <summary>
-        /// Get the associated value from the collection.  Multiple values will be merged.
+        /// Get the associated value from the collection.
-        /// Returns null if the key is not present.
+        /// Returns StringValues.Empty if the key is not present.
         /// </summary>
         /// <param name="key"></param>
         /// <returns></returns>
-        string this[string key] { get; }
+        StringValues this[string key] { get; }
 
         /// <summary>
         /// Gets the number of elements contained in the collection.
@@ -35,22 +35,5 @@ namespace Microsoft.AspNet.Http
         /// <param name="key"></param>
         /// <returns></returns>
         bool ContainsKey(string key);
-
-        /// <summary>
-        /// Get the associated value from the collection.  Multiple values will be merged.
-        /// Returns null if the key is not present.
-        /// </summary>
-        /// <param name="key"></param>
-        /// <returns></returns>
-        [SuppressMessage("Microsoft.Naming", "CA1716:IdentifiersShouldNotMatchKeywords", MessageId = "Get", Justification = "Re-evaluate later.")]
-        string Get(string key);
-
-        /// <summary>
-        /// Get the associated values from the collection in their original format.
-        /// Returns null if the key is not present.
-        /// </summary>
-        /// <param name="key"></param>
-        /// <returns></returns>
-        IList<string> GetValues(string key);
     }
 }

src/Microsoft.AspNet.Http.Abstractions/QueryString.cs

@@ -5,6 +5,7 @@ using System;
 using System.Collections.Generic;
 using System.Text;
 using Microsoft.Framework.Internal;
+using Microsoft.Framework.Primitives;
 using Microsoft.Framework.WebEncoders;
 
 namespace Microsoft.AspNet.Http
@@ -143,7 +144,7 @@ namespace Microsoft.AspNet.Http
         /// </summary>
         /// <param name="parameters"></param>
         /// <returns>The resulting QueryString</returns>
-        public static QueryString Create(IEnumerable<KeyValuePair<string, string[]>> parameters)
+        public static QueryString Create(IEnumerable<KeyValuePair<string, StringValues>> parameters)
         {
             var builder = new StringBuilder();
             bool first = true;

src/Microsoft.AspNet.Http.Extensions/HeaderDictionaryTypeExtensions.cs

@@ -7,6 +7,7 @@ using System.Linq;
 using System.Reflection;
 using Microsoft.AspNet.Http.Headers;
 using Microsoft.Framework.Internal;
+using Microsoft.Framework.Primitives;
 using Microsoft.Net.Http.Headers;
 
 namespace Microsoft.AspNet.Http
@@ -50,7 +51,7 @@ namespace Microsoft.AspNet.Http
             }
             else
             {
-                headers.SetValues(name, values.Select(value => value.ToString()).ToArray());
+                headers[name] = values.Select(value => value.ToString()).ToArray();
             }
         }
 
@@ -98,7 +99,7 @@ namespace Microsoft.AspNet.Http
             }
 
             var value = headers[name];
-            if (string.IsNullOrWhiteSpace(value))
+            if (StringValues.IsNullOrEmpty(value))
             {
                 return default(T);
             }
@@ -112,11 +113,11 @@ namespace Microsoft.AspNet.Http
             if (KnownListParsers.TryGetValue(typeof(T), out temp))
             {
                 var func = (Func<IList<string>, IList<T>>)temp;
-                return func(headers.GetValues(name));
+                return func(headers[name]);
             }
 
-            var values = headers.GetValues(name);
+            var values = headers[name];
-            if (values == null || !values.Any())
+            if (StringValues.IsNullOrEmpty(values))
             {
                 return null;
             }
@@ -158,7 +159,7 @@ namespace Microsoft.AspNet.Http
             return default(T);
         }
 
-        private static IList<T> GetListViaReflection<T>(IList<string> values)
+        private static IList<T> GetListViaReflection<T>(StringValues values)
         {
             // TODO: Cache the reflected type for later? Only if success?
             var type = typeof(T);

src/Microsoft.AspNet.Http.Extensions/RequestHeaders.cs

@@ -285,7 +285,7 @@ namespace Microsoft.AspNet.Http.Headers
 
         public void AppendList<T>([NotNull] string name, [NotNull] IList<T> values)
         {
-            Headers.AppendValues(name, values.Select(value => value.ToString()).ToArray());
+            Headers.Append(name, values.Select(value => value.ToString()).ToArray());
         }
     }
 }

src/Microsoft.AspNet.Http.Extensions/ResponseHeaders.cs

@@ -182,7 +182,7 @@ namespace Microsoft.AspNet.Http.Headers
 
         public void AppendList<T>([NotNull] string name, [NotNull] IList<T> values)
         {
-            Headers.AppendValues(name, values.Select(value => value.ToString()).ToArray());
+            Headers.Append(name, values.Select(value => value.ToString()).ToArray());
         }
     }
 }

src/Microsoft.AspNet.Http.Features/IHttpRequestFeature.cs

@@ -3,6 +3,7 @@
 
 using System.Collections.Generic;
 using System.IO;
+using Microsoft.Framework.Primitives;
 
 namespace Microsoft.AspNet.Http.Features
 {
@@ -14,7 +15,7 @@ namespace Microsoft.AspNet.Http.Features
         string PathBase { get; set; }
         string Path { get; set; }
         string QueryString { get; set; }
-        IDictionary<string, string[]> Headers { get; set; }
+        IDictionary<string, StringValues> Headers { get; set; }
         Stream Body { get; set; }
     }
 }

src/Microsoft.AspNet.Http.Features/IHttpResponseFeature.cs

@@ -5,6 +5,7 @@ using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Threading.Tasks;
+using Microsoft.Framework.Primitives;
 
 namespace Microsoft.AspNet.Http.Features
 {
@@ -12,7 +13,7 @@ namespace Microsoft.AspNet.Http.Features
     {
         int StatusCode { get; set; }
         string ReasonPhrase { get; set; }
-        IDictionary<string, string[]> Headers { get; set; }
+        IDictionary<string, StringValues> Headers { get; set; }
         Stream Body { get; set; }
         bool HasStarted { get; }
         void OnStarting(Func<object, Task> callback, object state);

src/Microsoft.AspNet.Http.Features/project.json

@@ -6,7 +6,11 @@
         "url": "git://github.com/aspnet/httpabstractions"
     },
     "dependencies": {
-        "Microsoft.Framework.NotNullAttribute.Sources": { "type": "build", "version": "1.0.0-*" }
+        "Microsoft.Framework.NotNullAttribute.Sources": {
+            "type": "build",
+            "version": "1.0.0-*"
+        },
+        "Microsoft.Framework.Primitives": "1.0.0-*"
     },
     "frameworks": {
         "dnx451": { },

src/Microsoft.AspNet.Http/DefaultHttpResponse.cs

@@ -68,8 +68,7 @@ namespace Microsoft.AspNet.Http.Internal
         {
             get
             {
-                var contentType = Headers[HeaderNames.ContentType];
+                return Headers[HeaderNames.ContentType];
-                return contentType;
             }
             set
             {
@@ -79,7 +78,7 @@ namespace Microsoft.AspNet.Http.Internal
                 }
                 else
                 {
-                    HttpResponseFeature.Headers[HeaderNames.ContentType] = new[] { value };
+                    HttpResponseFeature.Headers[HeaderNames.ContentType] = value;
                 }
             }
         }
@@ -115,7 +114,7 @@ namespace Microsoft.AspNet.Http.Internal
                 HttpResponseFeature.StatusCode = 302;
             }
 
-            Headers.Set(HeaderNames.Location, location);
+            Headers[HeaderNames.Location] = location;
         }
     }
 }

src/Microsoft.AspNet.Http/DefaultWebSocketManager.cs

@@ -12,8 +12,6 @@ namespace Microsoft.AspNet.Http.Internal
 {
     public class DefaultWebSocketManager : WebSocketManager
     {
-        private static IList<string> EmptyList = new List<string>();
-
         private IFeatureCollection _features;
         private FeatureReference<IHttpRequestFeature> _request = FeatureReference<IHttpRequestFeature>.Default;
         private FeatureReference<IHttpWebSocketFeature> _webSockets = FeatureReference<IHttpWebSocketFeature>.Default;
@@ -45,8 +43,7 @@ namespace Microsoft.AspNet.Http.Internal
         {
             get
             {
-                return ParsingHelpers.GetHeaderUnmodified(HttpRequestFeature.Headers,
+                return ParsingHelpers.GetHeaderSplit(HttpRequestFeature.Headers, HeaderNames.WebSocketSubProtocols);
-                    HeaderNames.WebSocketSubProtocols) ?? EmptyList;
             }
         }
 

src/Microsoft.AspNet.Http/Features/FormFeature.cs

@@ -10,6 +10,7 @@ using System.Threading.Tasks;
 using Microsoft.AspNet.Http.Internal;
 using Microsoft.AspNet.WebUtilities;
 using Microsoft.Framework.Internal;
+using Microsoft.Framework.Primitives;
 using Microsoft.Net.Http.Headers;
 
 namespace Microsoft.AspNet.Http.Features.Internal
@@ -87,7 +88,7 @@ namespace Microsoft.AspNet.Http.Features.Internal
 
             _request.EnableRewind();
 
-            IDictionary<string, string[]> formFields = null;
+            IDictionary<string, StringValues> formFields = null;
             var files = new FormFileCollection();
 
             // Some of these code paths use StreamReader which does not support cancellation tokens.
@@ -102,7 +103,7 @@ namespace Microsoft.AspNet.Http.Features.Internal
                 }
                 else if (HasMultipartFormContentType(contentType))
                 {
-                    var formAccumulator = new KeyValueAccumulator<string, string>(StringComparer.OrdinalIgnoreCase);
+                    var formAccumulator = new KeyValueAccumulator();
 
                     var boundary = GetBoundary(contentType);
                     var multipartReader = new MultipartReader(boundary, _request.Body);
@@ -111,7 +112,7 @@ namespace Microsoft.AspNet.Http.Features.Internal
                     {
                         var headers = new HeaderDictionary(section.Headers);
                         ContentDispositionHeaderValue contentDisposition;
-                        ContentDispositionHeaderValue.TryParse(headers.Get(HeaderNames.ContentDisposition), out contentDisposition);
+                        ContentDispositionHeaderValue.TryParse(headers[HeaderNames.ContentDisposition], out contentDisposition);
                         if (HasFileContentDisposition(contentDisposition))
                         {
                             // Find the end
@@ -131,7 +132,7 @@ namespace Microsoft.AspNet.Http.Features.Internal
 
                             var key = HeaderUtilities.RemoveQuotes(contentDisposition.Name);
                             MediaTypeHeaderValue mediaType;
-                            MediaTypeHeaderValue.TryParse(headers.Get(HeaderNames.ContentType), out mediaType);
+                            MediaTypeHeaderValue.TryParse(headers[HeaderNames.ContentType], out mediaType);
                             var encoding = FilterEncoding(mediaType?.Encoding);
                             using (var reader = new StreamReader(section.Body, encoding, detectEncodingFromByteOrderMarks: true, bufferSize: 1024, leaveOpen: true))
                             {
@@ -141,7 +142,7 @@ namespace Microsoft.AspNet.Http.Features.Internal
                         }
                         else
                         {
-                            System.Diagnostics.Debug.Assert(false, "Unrecognized content-disposition for this section: " + headers.Get(HeaderNames.ContentDisposition));
+                            System.Diagnostics.Debug.Assert(false, "Unrecognized content-disposition for this section: " + headers[HeaderNames.ContentDisposition]);
                         }
 
                         section = await multipartReader.ReadNextSectionAsync(cancellationToken);

src/Microsoft.AspNet.Http/Features/HttpRequestFeature.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using Microsoft.Framework.Primitives;
 
 namespace Microsoft.AspNet.Http.Features.Internal
 {
@@ -11,7 +12,7 @@ namespace Microsoft.AspNet.Http.Features.Internal
     {
         public HttpRequestFeature()
         {
-            Headers = new Dictionary<string, string[]>(StringComparer.OrdinalIgnoreCase);
+            Headers = new Dictionary<string, StringValues>(StringComparer.OrdinalIgnoreCase);
             Body = Stream.Null;
             Protocol = string.Empty;
             Scheme = string.Empty;
@@ -27,7 +28,7 @@ namespace Microsoft.AspNet.Http.Features.Internal
         public string PathBase { get; set; }
         public string Path { get; set; }
         public string QueryString { get; set; }
-        public IDictionary<string, string[]> Headers { get; set; }
+        public IDictionary<string, StringValues> Headers { get; set; }
         public Stream Body { get; set; }
     }
 }

src/Microsoft.AspNet.Http/Features/HttpResponseFeature.cs

@@ -5,6 +5,7 @@ using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Threading.Tasks;
+using Microsoft.Framework.Primitives;
 
 namespace Microsoft.AspNet.Http.Features.Internal
 {
@@ -13,7 +14,7 @@ namespace Microsoft.AspNet.Http.Features.Internal
         public HttpResponseFeature()
         {
             StatusCode = 200;
-            Headers = new Dictionary<string, string[]>(StringComparer.OrdinalIgnoreCase);
+            Headers = new Dictionary<string, StringValues>(StringComparer.OrdinalIgnoreCase);
             Body = Stream.Null;
         }
 
@@ -21,7 +22,7 @@ namespace Microsoft.AspNet.Http.Features.Internal
 
         public string ReasonPhrase { get; set; }
 
-        public IDictionary<string, string[]> Headers { get; set; }
+        public IDictionary<string, StringValues> Headers { get; set; }
 
         public Stream Body { get; set; }
 

src/Microsoft.AspNet.Http/Features/QueryFeature.cs

@@ -6,6 +6,7 @@ using System.Collections.Generic;
 using Microsoft.AspNet.Http.Internal;
 using Microsoft.AspNet.WebUtilities;
 using Microsoft.Framework.Internal;
+using Microsoft.Framework.Primitives;
 
 namespace Microsoft.AspNet.Http.Features.Internal
 {
@@ -13,17 +14,18 @@ namespace Microsoft.AspNet.Http.Features.Internal
     {
         private readonly IFeatureCollection _features;
         private FeatureReference<IHttpRequestFeature> _request = FeatureReference<IHttpRequestFeature>.Default;
-        private string _queryString;
-        private IReadableStringCollection _query;
 
-        public QueryFeature([NotNull] IDictionary<string, string[]> query)
+        private string _original;
-            : this (new ReadableStringCollection(query))
+        private IReadableStringCollection _parsedValues;
+
+        public QueryFeature([NotNull] IDictionary<string, StringValues> query)
+            : this(new ReadableStringCollection(query))
         {
         }
 
         public QueryFeature([NotNull] IReadableStringCollection query)
         {
-            _query = query;
+            _parsedValues = query;
         }
 
         public QueryFeature([NotNull] IFeatureCollection features)
@@ -37,24 +39,32 @@ namespace Microsoft.AspNet.Http.Features.Internal
             {
                 if (_features == null)
                 {
-                    return _query;
+                    return _parsedValues ?? ReadableStringCollection.Empty;
                 }
 
-                var queryString = _request.Fetch(_features).QueryString;
+                var current = _request.Fetch(_features).QueryString;
-                if (_query == null || !string.Equals(_queryString, queryString, StringComparison.Ordinal))
+                if (_parsedValues == null || !string.Equals(_original, current, StringComparison.Ordinal))
                 {
-                    _queryString = queryString;
+                    _original = current;
-                    _query = new ReadableStringCollection(QueryHelpers.ParseQuery(queryString));
+                    _parsedValues = new ReadableStringCollection(QueryHelpers.ParseQuery(current));
                 }
-                return _query;
+                return _parsedValues;
             }
             set
             {
-                _query = value;
+                _parsedValues = value;
                 if (_features != null)
                 {
-                    _queryString = _query == null ? string.Empty : QueryString.Create(_query).ToString();
+                    if (value == null)
-                    _request.Fetch(_features).QueryString = _queryString;
+                    {
+                        _original = string.Empty;
+                        _request.Fetch(_features).QueryString = string.Empty;
+                    }
+                    else
+                    {
+                        _original = QueryString.Create(_parsedValues).ToString();
+                        _request.Fetch(_features).QueryString = _original;
+                    }
                 }
             }
         }

src/Microsoft.AspNet.Http/Features/RequestCookiesFeature.cs

@@ -6,6 +6,7 @@ using System.Collections.Generic;
 using System.Linq;
 using Microsoft.AspNet.Http.Internal;
 using Microsoft.Framework.Internal;
+using Microsoft.Framework.Primitives;
 using Microsoft.Net.Http.Headers;
 
 namespace Microsoft.AspNet.Http.Features.Internal
@@ -14,18 +15,18 @@ namespace Microsoft.AspNet.Http.Features.Internal
     {
         private readonly IFeatureCollection _features;
         private readonly FeatureReference<IHttpRequestFeature> _request = FeatureReference<IHttpRequestFeature>.Default;
-        private string[] _cookieHeaders;
-        private RequestCookiesCollection _cookiesCollection;
-        private IReadableStringCollection _cookies;
 
-        public RequestCookiesFeature([NotNull] IDictionary<string, string[]> cookies)
+        private StringValues _original;
-            : this (new ReadableStringCollection(cookies))
+        private IReadableStringCollection _parsedValues;
+
+        public RequestCookiesFeature([NotNull] IDictionary<string, StringValues> cookies)
+            : this(new ReadableStringCollection(cookies))
         {
         }
 
         public RequestCookiesFeature([NotNull] IReadableStringCollection cookies)
         {
-            _cookies = cookies;
+            _parsedValues = cookies;
         }
 
         public RequestCookiesFeature([NotNull] IFeatureCollection features)
@@ -39,46 +40,53 @@ namespace Microsoft.AspNet.Http.Features.Internal
             {
                 if (_features == null)
                 {
-                    return _cookies;
+                    return _parsedValues ?? ReadableStringCollection.Empty;
                 }
 
                 var headers = _request.Fetch(_features).Headers;
-                string[] values;
+                StringValues current;
-                if (!headers.TryGetValue(HeaderNames.Cookie, out values))
+                if (!headers.TryGetValue(HeaderNames.Cookie, out current))
                 {
-                    values = new string[0];
+                    current = StringValues.Empty;
                 }
 
-                if (_cookieHeaders == null || !Enumerable.SequenceEqual(_cookieHeaders, values, StringComparer.Ordinal))
+                if (_parsedValues == null || !Enumerable.SequenceEqual(_original, current, StringComparer.Ordinal))
                 {
-                    _cookieHeaders = values;
+                    _original = current;
-                    if (_cookiesCollection == null)
+                    var collectionParser = _parsedValues as RequestCookiesCollection;
+                    if (collectionParser == null)
                     {
-                        _cookiesCollection = new RequestCookiesCollection();
+                        collectionParser = new RequestCookiesCollection();
-                        _cookies = _cookiesCollection;
+                        _parsedValues = collectionParser;
                     }
-                    _cookiesCollection.Reparse(values);
+                    collectionParser.Reparse(current);
                 }
 
-                return _cookies;
+                return _parsedValues;
             }
             set
             {
-                _cookies = value;
+                _parsedValues = value;
-                _cookieHeaders = null;
+                _original = StringValues.Empty;
-                _cookiesCollection = _cookies as RequestCookiesCollection;
+                if (_features != null)
-                if (_cookies != null && _features != null)
                 {
-                    var headers = new List<string>();
+                    if (_parsedValues == null || _parsedValues.Count == 0)
-                    foreach (var pair in _cookies)
                     {
-                        foreach (var cookieValue in pair.Value)
+                        _request.Fetch(_features).Headers.Remove(HeaderNames.Cookie);
-                        {
+                    }
-                            headers.Add(new CookieHeaderValue(pair.Key, cookieValue).ToString());
+                    else
-                        }
+                    {
+                        var headers = new List<string>();
+                        foreach (var pair in _parsedValues)
+                        {
+                            foreach (var cookieValue in pair.Value)
+                            {
+                                headers.Add(new CookieHeaderValue(pair.Key, cookieValue).ToString());
+                            }
+                        }
+                        _original = headers.ToArray();
+                        _request.Fetch(_features).Headers[HeaderNames.Cookie] = _original;
                     }
-                    _cookieHeaders = headers.ToArray();
-                    _request.Fetch(_features).Headers[HeaderNames.Cookie] = _cookieHeaders;
                 }
             }
         }

src/Microsoft.AspNet.Http/FormCollection.cs

@@ -3,6 +3,7 @@
 
 using System.Collections.Generic;
 using Microsoft.Framework.Internal;
+using Microsoft.Framework.Primitives;
 
 namespace Microsoft.AspNet.Http.Internal
 {
@@ -11,12 +12,12 @@ namespace Microsoft.AspNet.Http.Internal
     /// </summary>
     public class FormCollection : ReadableStringCollection, IFormCollection
     {
-        public FormCollection([NotNull] IDictionary<string, string[]> store)
+        public FormCollection([NotNull] IDictionary<string, StringValues> store)
             : this(store, new FormFileCollection())
         {
         }
 
-        public FormCollection([NotNull] IDictionary<string, string[]> store, [NotNull] IFormFileCollection files)
+        public FormCollection([NotNull] IDictionary<string, StringValues> store, [NotNull] IFormFileCollection files)
             : base(store)
         {
             Files = files;

src/Microsoft.AspNet.Http/HeaderDictionary.cs

@@ -4,9 +4,8 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
-using System.Linq;
-using Microsoft.AspNet.Http.Internal;
 using Microsoft.Framework.Internal;
+using Microsoft.Framework.Primitives;
 
 namespace Microsoft.AspNet.Http.Internal
 {
@@ -15,7 +14,7 @@ namespace Microsoft.AspNet.Http.Internal
     /// </summary>
     public class HeaderDictionary : IHeaderDictionary
     {
-        public HeaderDictionary() : this(new Dictionary<string, string[]>(StringComparer.OrdinalIgnoreCase))
+        public HeaderDictionary() : this(new Dictionary<string, StringValues>(StringComparer.OrdinalIgnoreCase))
         {
         }
 
@@ -23,12 +22,12 @@ namespace Microsoft.AspNet.Http.Internal
         /// Initializes a new instance of the <see cref="T:Microsoft.Owin.HeaderDictionary" /> class.
         /// </summary>
         /// <param name="store">The underlying data store.</param>
-        public HeaderDictionary([NotNull] IDictionary<string, string[]> store)
+        public HeaderDictionary([NotNull] IDictionary<string, StringValues> store)
         {
             Store = store;
         }
 
-        private IDictionary<string, string[]> Store { get; set; }
+        private IDictionary<string, StringValues> Store { get; set; }
 
         /// <summary>
         /// Gets an <see cref="T:System.Collections.ICollection" /> that contains the keys in the <see cref="T:Microsoft.Owin.HeaderDictionary" />;.
@@ -42,7 +41,7 @@ namespace Microsoft.AspNet.Http.Internal
         /// <summary>
         /// 
         /// </summary>
-        public ICollection<string[]> Values
+        public ICollection<StringValues> Values
         {
             get { return Store.Values; }
         }
@@ -69,11 +68,11 @@ namespace Microsoft.AspNet.Http.Internal
         /// Get or sets the associated value from the collection as a single string.
         /// </summary>
         /// <param name="key">The header name.</param>
-        /// <returns>the associated value from the collection as a single string or null if the key is not present.</returns>
+        /// <returns>the associated value from the collection as a StringValues or StringValues.Empty if the key is not present.</returns>
-        public string this[string key]
+        public StringValues this[string key]
         {
-            get { return Get(key); }
+            get { return ParsingHelpers.GetHeader(Store, key); }
-            set { Set(key, value); }
+            set { ParsingHelpers.SetHeader(Store, key, value); }
         }
 
         /// <summary>
@@ -81,7 +80,7 @@ namespace Microsoft.AspNet.Http.Internal
         /// </summary>
         /// <param name="key">The header name.</param>
         /// <returns></returns>
-        string[] IDictionary<string, string[]>.this[string key]
+        StringValues IDictionary<string, StringValues>.this[string key]
         {
             get { return Store[key]; }
             set { Store[key] = value; }
@@ -91,7 +90,7 @@ namespace Microsoft.AspNet.Http.Internal
         /// Returns an enumerator that iterates through a collection.
         /// </summary>
         /// <returns>An <see cref="T:System.Collections.IEnumerator" /> object that can be used to iterate through the collection.</returns>
-        public IEnumerator<KeyValuePair<string, string[]>> GetEnumerator()
+        IEnumerator<KeyValuePair<string, StringValues>> IEnumerable<KeyValuePair<string, StringValues>>.GetEnumerator()
         {
             return Store.GetEnumerator();
         }
@@ -102,59 +101,29 @@ namespace Microsoft.AspNet.Http.Internal
         /// <returns>An <see cref="T:System.Collections.IEnumerator" /> object that can be used to iterate through the collection.</returns>
         IEnumerator IEnumerable.GetEnumerator()
         {
-            return GetEnumerator();
+            return Store.GetEnumerator();
         }
 
-        /// <summary>
-        /// Get the associated value from the collection as a single string.
-        /// </summary>
-        /// <param name="key">The header name.</param>
-        /// <returns>the associated value from the collection as a single string or null if the key is not present.</returns>
-        public string Get(string key)
-        {
-            return ParsingHelpers.GetHeader(Store, key);
-        }
-
-        /// <summary>
-        /// Get the associated values from the collection without modification.
-        /// </summary>
-        /// <param name="key">The header name.</param>
-        /// <returns>the associated value from the collection without modification, or null if the key is not present.</returns>
-        public IList<string> GetValues(string key)
-        {
-            return ParsingHelpers.GetHeaderUnmodified(Store, key);
-        }
 
         /// <summary>
         /// Get the associated values from the collection separated into individual values.
         /// Quoted values will not be split, and the quotes will be removed.
         /// </summary>
         /// <param name="key">The header name.</param>
-        /// <returns>the associated values from the collection separated into individual values, or null if the key is not present.</returns>
+        /// <returns>the associated values from the collection separated into individual values, or StringValues.Empty if the key is not present.</returns>
-        public IList<string> GetCommaSeparatedValues(string key)
+        public StringValues GetCommaSeparatedValues(string key)
         {
-            IEnumerable<string> values = ParsingHelpers.GetHeaderSplit(Store, key);
+            return ParsingHelpers.GetHeaderSplit(Store, key);
-            return values == null ? null : values.ToList();
-        }
-
-        /// <summary>
-        /// Add a new value. Appends to the header if already present
-        /// </summary>
-        /// <param name="key">The header name.</param>
-        /// <param name="value">The header value.</param>
-        public void Append(string key, string value)
-        {
-            ParsingHelpers.AppendHeader(Store, key, value);
         }
 
         /// <summary>
         /// Add new values. Each item remains a separate array entry.
         /// </summary>
         /// <param name="key">The header name.</param>
-        /// <param name="values">The header values.</param>
+        /// <param name="value">The header value.</param>
-        public void AppendValues(string key, params string[] values)
+        public void Append(string key, StringValues value)
         {
-            ParsingHelpers.AppendHeaderUnmodified(Store, key, values);
+            ParsingHelpers.AppendHeaderUnmodified(Store, key, value);
         }
 
         /// <summary>
@@ -167,26 +136,6 @@ namespace Microsoft.AspNet.Http.Internal
             ParsingHelpers.AppendHeaderJoined(Store, key, values);
         }
 
-        /// <summary>
-        /// Sets a specific header value.
-        /// </summary>
-        /// <param name="key">The header name.</param>
-        /// <param name="value">The header value.</param>
-        public void Set(string key, string value)
-        {
-            ParsingHelpers.SetHeader(Store, key, value);
-        }
-
-        /// <summary>
-        /// Sets the specified header values without modification.
-        /// </summary>
-        /// <param name="key">The header name.</param>
-        /// <param name="values">The header values.</param>
-        public void SetValues(string key, params string[] values)
-        {
-            ParsingHelpers.SetHeaderUnmodified(Store, key, values);
-        }
-
         /// <summary>
         /// Quotes any values containing comas, and then coma joins all of the values.
         /// </summary>
@@ -202,7 +151,7 @@ namespace Microsoft.AspNet.Http.Internal
         /// </summary>
         /// <param name="key">The header name.</param>
         /// <param name="value">The header values.</param>
-        public void Add(string key, string[] value)
+        public void Add(string key, StringValues value)
         {
             Store.Add(key, value);
         }
@@ -233,7 +182,7 @@ namespace Microsoft.AspNet.Http.Internal
         /// <param name="key">The header name.</param>
         /// <param name="value">The value.</param>
         /// <returns>true if the <see cref="T:Microsoft.Owin.HeaderDictionary" /> contains the key; otherwise, false.</returns>
-        public bool TryGetValue(string key, out string[] value)
+        public bool TryGetValue(string key, out StringValues value)
         {
             return Store.TryGetValue(key, out value);
         }
@@ -242,7 +191,7 @@ namespace Microsoft.AspNet.Http.Internal
         /// Adds a new list of items to the collection.
         /// </summary>
         /// <param name="item">The item to add.</param>
-        public void Add(KeyValuePair<string, string[]> item)
+        public void Add(KeyValuePair<string, StringValues> item)
         {
             Store.Add(item);
         }
@@ -260,7 +209,7 @@ namespace Microsoft.AspNet.Http.Internal
         /// </summary>
         /// <param name="item">The item.</param>
         /// <returns>true if the specified object occurs within this collection; otherwise, false.</returns>
-        public bool Contains(KeyValuePair<string, string[]> item)
+        public bool Contains(KeyValuePair<string, StringValues> item)
         {
             return Store.Contains(item);
         }
@@ -270,7 +219,7 @@ namespace Microsoft.AspNet.Http.Internal
         /// </summary>
         /// <param name="array">The one-dimensional Array that is the destination of the specified objects copied from the <see cref="T:Microsoft.Owin.HeaderDictionary" />.</param>
         /// <param name="arrayIndex">The zero-based index in <paramref name="array" /> at which copying begins.</param>
-        public void CopyTo(KeyValuePair<string, string[]>[] array, int arrayIndex)
+        public void CopyTo(KeyValuePair<string, StringValues>[] array, int arrayIndex)
         {
             Store.CopyTo(array, arrayIndex);
         }
@@ -280,7 +229,7 @@ namespace Microsoft.AspNet.Http.Internal
         /// </summary>
         /// <param name="item">The item.</param>
         /// <returns>true if the specified object was removed from the collection; otherwise, false.</returns>
-        public bool Remove(KeyValuePair<string, string[]> item)
+        public bool Remove(KeyValuePair<string, StringValues> item)
         {
             return Store.Remove(item);
         }

src/Microsoft.AspNet.Http/ParsingHelpers.cs

@@ -7,6 +7,7 @@ using System.Collections.Generic;
 using System.Globalization;
 using System.Linq;
 using Microsoft.Framework.Internal;
+using Microsoft.Framework.Primitives;
 using Microsoft.Net.Http.Headers;
 
 namespace Microsoft.AspNet.Http.Internal
@@ -76,9 +77,9 @@ namespace Microsoft.AspNet.Http.Internal
     [System.CodeDom.Compiler.GeneratedCode("App_Packages", "")]
     internal struct HeaderSegmentCollection : IEnumerable<HeaderSegment>, IEquatable<HeaderSegmentCollection>
     {
-        private readonly string[] _headers;
+        private readonly StringValues _headers;
 
-        public HeaderSegmentCollection(string[] headers)
+        public HeaderSegmentCollection(StringValues headers)
         {
             _headers = headers;
         }
@@ -102,7 +103,7 @@ namespace Microsoft.AspNet.Http.Internal
 
         public override int GetHashCode()
         {
-            return (_headers != null ? _headers.GetHashCode() : 0);
+            return (!StringValues.IsNullOrEmpty(_headers) ? _headers.GetHashCode() : 0);
         }
 
         public static bool operator ==(HeaderSegmentCollection left, HeaderSegmentCollection right)
@@ -134,7 +135,7 @@ namespace Microsoft.AspNet.Http.Internal
 
         internal struct Enumerator : IEnumerator<HeaderSegment>
         {
-            private readonly string[] _headers;
+            private readonly StringValues _headers;
             private int _index;
 
             private string _header;
@@ -149,11 +150,9 @@ namespace Microsoft.AspNet.Http.Internal
 
             private Mode _mode;
 
-            private static readonly string[] NoHeaders = new string[0];
+            public Enumerator(StringValues headers)
-
-            public Enumerator(string[] headers)
             {
-                _headers = headers ?? NoHeaders;
+                _headers = headers;
                 _header = string.Empty;
                 _headerLength = -1;
                 _index = -1;
@@ -237,7 +236,7 @@ namespace Microsoft.AspNet.Http.Internal
                         _trailingStart = -1;
 
                         // if that was the last string
-                        if (_index == _headers.Length)
+                        if (_index == _headers.Count)
                         {
                             // no more move nexts
                             return false;
@@ -496,19 +495,19 @@ namespace Microsoft.AspNet.Http.Internal
 
     internal static class ParsingHelpers
     {
-        public static string GetHeader(IDictionary<string, string[]> headers, string key)
+        public static StringValues GetHeader(IDictionary<string, StringValues> headers, string key)
         {
-            string[] values = GetHeaderUnmodified(headers, key);
+            StringValues value;
-            return values == null ? null : string.Join(",", values);
+            return headers.TryGetValue(key, out value) ? value : StringValues.Empty;
         }
 
-        public static IEnumerable<string> GetHeaderSplit(IDictionary<string, string[]> headers, string key)
+        public static StringValues GetHeaderSplit(IDictionary<string, StringValues> headers, string key)
         {
-            string[] values = GetHeaderUnmodified(headers, key);
+            var values = GetHeaderUnmodified(headers, key);
-            return values == null ? null : GetHeaderSplitImplementation(values);
+            return new StringValues(GetHeaderSplitImplementation(values).ToArray());
         }
 
-        private static IEnumerable<string> GetHeaderSplitImplementation(string[] values)
+        private static IEnumerable<string> GetHeaderSplitImplementation(StringValues values)
         {
             foreach (var segment in new HeaderSegmentCollection(values))
             {
@@ -519,41 +518,41 @@ namespace Microsoft.AspNet.Http.Internal
             }
         }
 
-        public static string[] GetHeaderUnmodified([NotNull] IDictionary<string, string[]> headers, string key)
+        public static StringValues GetHeaderUnmodified([NotNull] IDictionary<string, StringValues> headers, string key)
         {
-            string[] values;
+            StringValues values;
-            return headers.TryGetValue(key, out values) ? values : null;
+            return headers.TryGetValue(key, out values) ? values : StringValues.Empty;
         }
 
-        public static void SetHeader([NotNull] IDictionary<string, string[]> headers, [NotNull] string key, string value)
+        public static void SetHeader([NotNull] IDictionary<string, StringValues> headers, [NotNull] string key, StringValues value)
         {
             if (string.IsNullOrWhiteSpace(key))
             {
                 throw new ArgumentNullException(nameof(key));
             }
-            if (string.IsNullOrWhiteSpace(value))
+            if (StringValues.IsNullOrEmpty(value))
             {
                 headers.Remove(key);
             }
             else
             {
-                headers[key] = new[] { value };
+                headers[key] = value;
             }
         }
 
-        public static void SetHeaderJoined([NotNull] IDictionary<string, string[]> headers, [NotNull] string key, params string[] values)
+        public static void SetHeaderJoined([NotNull] IDictionary<string, StringValues> headers, [NotNull] string key, StringValues value)
         {
             if (string.IsNullOrWhiteSpace(key))
             {
                 throw new ArgumentNullException(nameof(key));
             }
-            if (values == null || values.Length == 0)
+            if (StringValues.IsNullOrEmpty(value))
             {
                 headers.Remove(key);
             }
             else
             {
-                headers[key] = new[] { string.Join(",", values.Select(value => QuoteIfNeeded(value))) };
+                headers[key] = string.Join(",", value.Select(QuoteIfNeeded));
             }
         }
 
@@ -589,46 +588,23 @@ namespace Microsoft.AspNet.Http.Internal
             return value;
         }
 
-        public static void SetHeaderUnmodified([NotNull] IDictionary<string, string[]> headers, [NotNull] string key, params string[] values)
+        public static void SetHeaderUnmodified([NotNull] IDictionary<string, StringValues> headers, [NotNull] string key, StringValues? values)
         {
             if (string.IsNullOrWhiteSpace(key))
             {
                 throw new ArgumentNullException(nameof(key));
             }
-            if (values == null || values.Length == 0)
+            if (!values.HasValue || StringValues.IsNullOrEmpty(values.Value))
             {
                 headers.Remove(key);
             }
             else
             {
-                headers[key] = values;
+                headers[key] = values.Value;
             }
         }
 
-        public static void SetHeaderUnmodified([NotNull] IDictionary<string, string[]> headers, [NotNull] string key, [NotNull] IEnumerable<string> values)
+        public static void AppendHeaderJoined([NotNull] IDictionary<string, StringValues> headers, [NotNull] string key, params string[] values)
-        {
-            headers[key] = values.ToArray();
-        }
-
-        public static void AppendHeader([NotNull] IDictionary<string, string[]> headers, [NotNull] string key, string values)
-        {
-            if (string.IsNullOrWhiteSpace(values))
-            {
-                return;
-            }
-
-            string existing = GetHeader(headers, key);
-            if (existing == null)
-            {
-                SetHeader(headers, key, values);
-            }
-            else
-            {
-                headers[key] = new[] { existing + "," + values };
-            }
-        }
-
-        public static void AppendHeaderJoined([NotNull] IDictionary<string, string[]> headers, [NotNull] string key, params string[] values)
         {
             if (values == null || values.Length == 0)
             {
@@ -642,35 +618,29 @@ namespace Microsoft.AspNet.Http.Internal
             }
             else
             {
-                headers[key] = new[] { existing + "," + string.Join(",", values.Select(value => QuoteIfNeeded(value))) };
+                headers[key] = existing + "," + string.Join(",", values.Select(value => QuoteIfNeeded(value)));
             }
         }
 
-        public static void AppendHeaderUnmodified([NotNull] IDictionary<string, string[]> headers, [NotNull] string key, params string[] values)
+        public static void AppendHeaderUnmodified([NotNull] IDictionary<string, StringValues> headers, [NotNull] string key, StringValues values)
         {
-            if (values == null || values.Length == 0)
+            if (values.Count == 0)
             {
                 return;
             }
 
-            string[] existing = GetHeaderUnmodified(headers, key);
+            var existing = GetHeaderUnmodified(headers, key);
-            if (existing == null)
+            SetHeaderUnmodified(headers, key, StringValues.Concat(existing, values));
-            {
-                SetHeaderUnmodified(headers, key, values);
-            }
-            else
-            {
-                SetHeaderUnmodified(headers, key, existing.Concat(values));
-            }
         }
 
         public static long? GetContentLength([NotNull] IHeaderDictionary headers)
         {
             const NumberStyles styles = NumberStyles.AllowLeadingWhite | NumberStyles.AllowTrailingWhite;
             long value;
-            string rawValue = headers.Get(HeaderNames.ContentLength);
+            var rawValue = headers[HeaderNames.ContentLength];
-            if (!string.IsNullOrWhiteSpace(rawValue) &&
+            if (rawValue.Count == 1 &&
-                long.TryParse(rawValue, styles, CultureInfo.InvariantCulture, out value))
+                !string.IsNullOrWhiteSpace(rawValue[0]) &&
+                long.TryParse(rawValue[0], styles, CultureInfo.InvariantCulture, out value))
             {
                 return value;
             }

src/Microsoft.AspNet.Http/ReadableStringCollection.cs

@@ -4,6 +4,7 @@
 using System.Collections;
 using System.Collections.Generic;
 using Microsoft.Framework.Internal;
+using Microsoft.Framework.Primitives;
 
 namespace Microsoft.AspNet.Http.Internal
 {
@@ -12,16 +13,18 @@ namespace Microsoft.AspNet.Http.Internal
     /// </summary>
     public class ReadableStringCollection : IReadableStringCollection
     {
+        public static readonly IReadableStringCollection Empty = new ReadableStringCollection(new Dictionary<string, StringValues>(0));
+
         /// <summary>
         /// Create a new wrapper
         /// </summary>
         /// <param name="store"></param>
-        public ReadableStringCollection([NotNull] IDictionary<string, string[]> store)
+        public ReadableStringCollection([NotNull] IDictionary<string, StringValues> store)
         {
             Store = store;
         }
 
-        private IDictionary<string, string[]> Store { get; set; }
+        private IDictionary<string, StringValues> Store { get; set; }
 
         /// <summary>
         /// Gets the number of elements contained in the collection.
@@ -42,13 +45,21 @@ namespace Microsoft.AspNet.Http.Internal
 
         /// <summary>
         /// Get the associated value from the collection.  Multiple values will be merged.
-        /// Returns null if the key is not present.
+        /// Returns StringValues.Empty if the key is not present.
         /// </summary>
         /// <param name="key"></param>
         /// <returns></returns>
-        public string this[string key]
+        public StringValues this[string key]
         {
-            get { return Get(key); }
+            get
+            {
+                StringValues value;
+                if (Store.TryGetValue(key, out value))
+                {
+                    return value;
+                }
+                return StringValues.Empty;
+            }
         }
 
         /// <summary>
@@ -61,35 +72,12 @@ namespace Microsoft.AspNet.Http.Internal
             return Store.ContainsKey(key);
         }
 
-        /// <summary>
-        /// Get the associated value from the collection.  Multiple values will be merged.
-        /// Returns null if the key is not present.
-        /// </summary>
-        /// <param name="key"></param>
-        /// <returns></returns>
-        public string Get(string key)
-        {
-            return GetJoinedValue(Store, key);
-        }
-
-        /// <summary>
-        /// Get the associated values from the collection in their original format.
-        /// Returns null if the key is not present.
-        /// </summary>
-        /// <param name="key"></param>
-        /// <returns></returns>
-        public IList<string> GetValues(string key)
-        {
-            string[] values;
-            Store.TryGetValue(key, out values);
-            return values;
-        }
 
         /// <summary>
         /// 
         /// </summary>
         /// <returns></returns>
-        public IEnumerator<KeyValuePair<string, string[]>> GetEnumerator()
+        public IEnumerator<KeyValuePair<string, StringValues>> GetEnumerator()
         {
             return Store.GetEnumerator();
         }
@@ -102,15 +90,5 @@ namespace Microsoft.AspNet.Http.Internal
         {
             return GetEnumerator();
         }
-
-        private static string GetJoinedValue(IDictionary<string, string[]> store, string key)
-        {
-            string[] values;
-            if (store.TryGetValue(key, out values))
-            {
-                return string.Join(",", values);
-            }
-            return null;
-        }
     }
 }

src/Microsoft.AspNet.Http/RequestCookiesCollection.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
+using Microsoft.Framework.Primitives;
 using Microsoft.Net.Http.Headers;
 
 namespace Microsoft.AspNet.Http.Internal
@@ -17,7 +18,7 @@ namespace Microsoft.AspNet.Http.Internal
             _dictionary = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
         }
 
-        public string this[string key]
+        public StringValues this[string key]
         {
             get { return Get(key); }
         }
@@ -88,11 +89,11 @@ namespace Microsoft.AspNet.Http.Internal
             }
         }
 
-        public IEnumerator<KeyValuePair<string, string[]>> GetEnumerator()
+        public IEnumerator<KeyValuePair<string, StringValues>> GetEnumerator()
         {
             foreach (var pair in _dictionary)
             {
-                yield return new KeyValuePair<string, string[]>(pair.Key, new[] { pair.Value });
+                yield return new KeyValuePair<string, StringValues>(pair.Key, pair.Value);
             }
         }
 

src/Microsoft.AspNet.Http/ResponseCookies.cs

@@ -2,9 +2,9 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.Collections.Generic;
 using System.Linq;
 using Microsoft.Framework.Internal;
+using Microsoft.Framework.Primitives;
 using Microsoft.Framework.WebEncoders;
 using Microsoft.Net.Http.Headers;
 
@@ -33,11 +33,14 @@ namespace Microsoft.AspNet.Http.Internal
         /// <param name="value"></param>
         public void Append(string key, string value)
         {
-            Headers.AppendValues(HeaderNames.SetCookie,
+            var setCookieHeaderValue = new SetCookieHeaderValue(
-                new SetCookieHeaderValue(
                     UrlEncoder.Default.UrlEncode(key),
                     UrlEncoder.Default.UrlEncode(value))
-                    { Path = "/" }.ToString());
+            {
+                Path = "/"
+            };
+
+            Headers[HeaderNames.SetCookie] = StringValues.Concat(Headers[HeaderNames.SetCookie], setCookieHeaderValue.ToString());
         }
 
         /// <summary>
@@ -48,17 +51,18 @@ namespace Microsoft.AspNet.Http.Internal
         /// <param name="options"></param>
         public void Append(string key, string value, [NotNull] CookieOptions options)
         {
-            Headers.AppendValues(HeaderNames.SetCookie,
+            var setCookieHeaderValue = new SetCookieHeaderValue(
-                new SetCookieHeaderValue(
                     UrlEncoder.Default.UrlEncode(key),
                     UrlEncoder.Default.UrlEncode(value))
-                {
+            {
-                    Domain = options.Domain,
+                Domain = options.Domain,
-                    Path = options.Path,
+                Path = options.Path,
-                    Expires = options.Expires,
+                Expires = options.Expires,
-                    Secure = options.Secure,
+                Secure = options.Secure,
-                    HttpOnly = options.HttpOnly,
+                HttpOnly = options.HttpOnly,
-                }.ToString());
+            };
+
+            Headers[HeaderNames.SetCookie] = StringValues.Concat(Headers[HeaderNames.SetCookie], setCookieHeaderValue.ToString());
         }
 
         /// <summary>
@@ -70,15 +74,15 @@ namespace Microsoft.AspNet.Http.Internal
             var encodedKeyPlusEquals = UrlEncoder.Default.UrlEncode(key) + "=";
             Func<string, bool> predicate = value => value.StartsWith(encodedKeyPlusEquals, StringComparison.OrdinalIgnoreCase);
 
-            var deleteCookies = new[] { encodedKeyPlusEquals + "; expires=Thu, 01-Jan-1970 00:00:00 GMT" };
+            StringValues deleteCookies = encodedKeyPlusEquals + "; expires=Thu, 01-Jan-1970 00:00:00 GMT";
-            IList<string> existingValues = Headers.GetValues(HeaderNames.SetCookie);
+            var existingValues = Headers[HeaderNames.SetCookie];
-            if (existingValues == null || existingValues.Count == 0)
+            if (StringValues.IsNullOrEmpty(existingValues))
             {
-                Headers.SetValues(HeaderNames.SetCookie, deleteCookies);
+                Headers[HeaderNames.SetCookie] = deleteCookies;
             }
             else
             {
-                Headers.SetValues(HeaderNames.SetCookie, existingValues.Where(value => !predicate(value)).Concat(deleteCookies).ToArray());
+                Headers[HeaderNames.SetCookie] = existingValues.Where(value => !predicate(value)).Concat(deleteCookies).ToArray();
             }
         }
 
@@ -111,10 +115,10 @@ namespace Microsoft.AspNet.Http.Internal
                 rejectPredicate = value => value.StartsWith(encodedKeyPlusEquals, StringComparison.OrdinalIgnoreCase);
             }
 
-            IList<string> existingValues = Headers.GetValues(HeaderNames.SetCookie);
+            var existingValues = Headers[HeaderNames.SetCookie];
-            if (existingValues != null)
+            if (!StringValues.IsNullOrEmpty(existingValues))
             {
-                Headers.SetValues(HeaderNames.SetCookie, existingValues.Where(value => !rejectPredicate(value)).ToArray());
+                Headers[HeaderNames.SetCookie] = existingValues.Where(value => !rejectPredicate(value)).ToArray();
             }
 
             Append(key, string.Empty, new CookieOptions

src/Microsoft.AspNet.Owin/DictionaryStringArrayWrapper.cs

@@ -0,0 +1,80 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.Framework.Primitives;
+
+namespace Microsoft.AspNet.Owin
+{
+    internal class DictionaryStringArrayWrapper : IDictionary<string, string[]>
+    {
+        public DictionaryStringArrayWrapper(IDictionary<string, StringValues> inner)
+        {
+            Inner = inner;
+        }
+
+        public readonly IDictionary<string, StringValues> Inner;
+
+        private KeyValuePair<string, StringValues> Convert(KeyValuePair<string, string[]> item) => new KeyValuePair<string, StringValues>(item.Key, item.Value);
+
+        private KeyValuePair<string, string[]> Convert(KeyValuePair<string, StringValues> item) => new KeyValuePair<string, string[]>(item.Key, item.Value);
+
+        private StringValues Convert(string[] item) => item;
+
+        private string[] Convert(StringValues item) => item;
+
+        string[] IDictionary<string, string[]>.this[string key]
+        {
+            get { return Inner[key]; }
+            set { Inner[key] = value; }
+        }
+
+        int ICollection<KeyValuePair<string, string[]>>.Count => Inner.Count;
+
+        bool ICollection<KeyValuePair<string, string[]>>.IsReadOnly => Inner.IsReadOnly;
+
+        ICollection<string> IDictionary<string, string[]>.Keys => Inner.Keys;
+
+        ICollection<string[]> IDictionary<string, string[]>.Values => Inner.Values.Select(Convert).ToList();
+
+        void ICollection<KeyValuePair<string, string[]>>.Add(KeyValuePair<string, string[]> item) => Inner.Add(Convert(item));
+
+        void IDictionary<string, string[]>.Add(string key, string[] value) => Inner.Add(key, value);
+
+        void ICollection<KeyValuePair<string, string[]>>.Clear() => Inner.Clear();
+
+        bool ICollection<KeyValuePair<string, string[]>>.Contains(KeyValuePair<string, string[]> item) => Inner.Contains(Convert(item));
+
+        bool IDictionary<string, string[]>.ContainsKey(string key) => Inner.ContainsKey(key);
+
+        void ICollection<KeyValuePair<string, string[]>>.CopyTo(KeyValuePair<string, string[]>[] array, int arrayIndex)
+        {
+            foreach(var kv in Inner)
+            {
+                array[arrayIndex++] = Convert(kv);
+            }
+        }
+
+        IEnumerator IEnumerable.GetEnumerator() => Inner.Select(Convert).GetEnumerator();
+
+        IEnumerator<KeyValuePair<string, string[]>> IEnumerable<KeyValuePair<string, string[]>>.GetEnumerator() => Inner.Select(Convert).GetEnumerator();
+
+        bool ICollection<KeyValuePair<string, string[]>>.Remove(KeyValuePair<string, string[]> item) => Inner.Remove(Convert(item));
+
+        bool IDictionary<string, string[]>.Remove(string key) => Inner.Remove(key);
+
+        bool IDictionary<string, string[]>.TryGetValue(string key, out string[] value)
+        {
+            StringValues temp;
+            if (Inner.TryGetValue(key, out temp))
+            {
+                value = temp;
+                return true;
+            }
+            value = default(StringValues);
+            return false;
+        }
+    }
+}

src/Microsoft.AspNet.Owin/DictionaryStringValuesWrapper.cs

@@ -0,0 +1,80 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.Framework.Primitives;
+
+namespace Microsoft.AspNet.Owin
+{
+    internal class DictionaryStringValuesWrapper : IDictionary<string, StringValues>
+    {
+        public DictionaryStringValuesWrapper(IDictionary<string, string[]> inner)
+        {
+            Inner = inner;
+        }
+
+        public readonly IDictionary<string, string[]> Inner;
+
+        private KeyValuePair<string, StringValues> Convert(KeyValuePair<string, string[]> item) => new KeyValuePair<string, StringValues>(item.Key, item.Value);
+
+        private KeyValuePair<string, string[]> Convert(KeyValuePair<string, StringValues> item) => new KeyValuePair<string, string[]>(item.Key, item.Value);
+
+        private StringValues Convert(string[] item) => item;
+
+        private string[] Convert(StringValues item) => item;
+
+        StringValues IDictionary<string, StringValues>.this[string key]
+        {
+            get { return Inner[key]; }
+            set { Inner[key] = value; }
+        }
+
+        int ICollection<KeyValuePair<string, StringValues>>.Count => Inner.Count;
+
+        bool ICollection<KeyValuePair<string, StringValues>>.IsReadOnly => Inner.IsReadOnly;
+
+        ICollection<string> IDictionary<string, StringValues>.Keys => Inner.Keys;
+
+        ICollection<StringValues> IDictionary<string, StringValues>.Values => Inner.Values.Select(Convert).ToList();
+
+        void ICollection<KeyValuePair<string, StringValues>>.Add(KeyValuePair<string, StringValues> item) => Inner.Add(Convert(item));
+
+        void IDictionary<string, StringValues>.Add(string key, StringValues value) => Inner.Add(key, value);
+
+        void ICollection<KeyValuePair<string, StringValues>>.Clear() => Inner.Clear();
+
+        bool ICollection<KeyValuePair<string, StringValues>>.Contains(KeyValuePair<string, StringValues> item) => Inner.Contains(Convert(item));
+
+        bool IDictionary<string, StringValues>.ContainsKey(string key) => Inner.ContainsKey(key);
+
+        void ICollection<KeyValuePair<string, StringValues>>.CopyTo(KeyValuePair<string, StringValues>[] array, int arrayIndex)
+        {
+            foreach (var kv in Inner)
+            {
+                array[arrayIndex++] = Convert(kv);
+            }
+        }
+
+        IEnumerator IEnumerable.GetEnumerator() => Inner.Select(Convert).GetEnumerator();
+
+        IEnumerator<KeyValuePair<string, StringValues>> IEnumerable<KeyValuePair<string, StringValues>>.GetEnumerator() => Inner.Select(Convert).GetEnumerator();
+
+        bool ICollection<KeyValuePair<string, StringValues>>.Remove(KeyValuePair<string, StringValues> item) => Inner.Remove(Convert(item));
+
+        bool IDictionary<string, StringValues>.Remove(string key) => Inner.Remove(key);
+
+        bool IDictionary<string, StringValues>.TryGetValue(string key, out StringValues value)
+        {
+            string[] temp;
+            if (Inner.TryGetValue(key, out temp))
+            {
+                value = temp;
+                return true;
+            }
+            value = default(StringValues);
+            return false;
+        }
+    }
+}

src/Microsoft.AspNet.Owin/OwinEnvironment.cs

@@ -56,13 +56,13 @@ namespace Microsoft.AspNet.Owin
                 { OwinConstants.RequestPath, new FeatureMap<IHttpRequestFeature>(feature => feature.Path, () => string.Empty, (feature, value) => feature.Path = Convert.ToString(value)) },
                 { OwinConstants.RequestQueryString, new FeatureMap<IHttpRequestFeature>(feature => Utilities.RemoveQuestionMark(feature.QueryString), () => string.Empty,
                     (feature, value) => feature.QueryString = Utilities.AddQuestionMark(Convert.ToString(value))) },
-                { OwinConstants.RequestHeaders, new FeatureMap<IHttpRequestFeature>(feature => feature.Headers, (feature, value) => feature.Headers = (IDictionary<string, string[]>)value) },
+                { OwinConstants.RequestHeaders, new FeatureMap<IHttpRequestFeature>(feature => Utilities.MakeDictionaryStringArray(feature.Headers), (feature, value) => feature.Headers = Utilities.MakeDictionaryStringValues((IDictionary<string, string[]>)value)) },
                 { OwinConstants.RequestBody, new FeatureMap<IHttpRequestFeature>(feature => feature.Body, () => Stream.Null, (feature, value) => feature.Body = (Stream)value) },
                 { OwinConstants.RequestUser, new FeatureMap<IHttpAuthenticationFeature>(feature => feature.User, () => null, (feature, value) => feature.User = (ClaimsPrincipal)value) },
 
                 { OwinConstants.ResponseStatusCode, new FeatureMap<IHttpResponseFeature>(feature => feature.StatusCode, () => 200, (feature, value) => feature.StatusCode = Convert.ToInt32(value)) },
                 { OwinConstants.ResponseReasonPhrase, new FeatureMap<IHttpResponseFeature>(feature => feature.ReasonPhrase, (feature, value) => feature.ReasonPhrase = Convert.ToString(value)) },
-                { OwinConstants.ResponseHeaders, new FeatureMap<IHttpResponseFeature>(feature => feature.Headers, (feature, value) => feature.Headers = (IDictionary<string, string[]>)value) },
+                { OwinConstants.ResponseHeaders, new FeatureMap<IHttpResponseFeature>(feature => Utilities.MakeDictionaryStringArray(feature.Headers), (feature, value) => feature.Headers = Utilities.MakeDictionaryStringValues((IDictionary<string, string[]>)value)) },
                 { OwinConstants.ResponseBody, new FeatureMap<IHttpResponseFeature>(feature => feature.Body, () => Stream.Null, (feature, value) => feature.Body = (Stream)value) },
                 { OwinConstants.CommonKeys.OnSendingHeaders, new FeatureMap<IHttpResponseFeature>(
                     feature => new Action<Action<object>, object>((cb, state) => {

src/Microsoft.AspNet.Owin/OwinFeatureCollection.cs

@@ -14,8 +14,10 @@ using System.Security.Cryptography.X509Certificates;
 using System.Security.Principal;
 using System.Threading;
 using System.Threading.Tasks;
+using Microsoft.AspNet.Http;
 using Microsoft.AspNet.Http.Features;
 using Microsoft.AspNet.Http.Features.Authentication;
+using Microsoft.Framework.Primitives;
 
 namespace Microsoft.AspNet.Owin
 {
@@ -104,10 +106,10 @@ namespace Microsoft.AspNet.Owin
             set { Prop(OwinConstants.RequestQueryString, Utilities.RemoveQuestionMark(value)); }
         }
 
-        IDictionary<string, string[]> IHttpRequestFeature.Headers
+        IDictionary<string, StringValues> IHttpRequestFeature.Headers
         {
-            get { return Prop<IDictionary<string, string[]>>(OwinConstants.RequestHeaders); }
+            get { return Utilities.MakeDictionaryStringValues(Prop<IDictionary<string, string[]>>(OwinConstants.RequestHeaders)); }
-            set { Prop(OwinConstants.RequestHeaders, value); }
+            set { Prop(OwinConstants.RequestHeaders, Utilities.MakeDictionaryStringArray(value)); }
         }
 
         string IHttpRequestIdentifierFeature.TraceIdentifier
@@ -134,10 +136,10 @@ namespace Microsoft.AspNet.Owin
             set { Prop(OwinConstants.ResponseReasonPhrase, value); }
         }
 
-        IDictionary<string, string[]> IHttpResponseFeature.Headers
+        IDictionary<string, StringValues> IHttpResponseFeature.Headers
         {
-            get { return Prop<IDictionary<string, string[]>>(OwinConstants.ResponseHeaders); }
+            get { return Utilities.MakeDictionaryStringValues(Prop<IDictionary<string, string[]>>(OwinConstants.ResponseHeaders)); }
-            set { Prop(OwinConstants.ResponseHeaders, value); }
+            set { Prop(OwinConstants.ResponseHeaders, Utilities.MakeDictionaryStringArray(value)); }
         }
 
         Stream IHttpResponseFeature.Body

src/Microsoft.AspNet.Owin/Utilities.cs

@@ -1,8 +1,12 @@
 // Copyright (c) .NET Foundation. 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.Security.Claims;
 using System.Security.Principal;
+using Microsoft.AspNet.Http;
+using Microsoft.Framework.Primitives;
 
 namespace Microsoft.AspNet.Owin
 {
@@ -41,5 +45,25 @@ namespace Microsoft.AspNet.Owin
             }
             return new ClaimsPrincipal(principal);
         }
+
+        internal static IDictionary<string, StringValues> MakeDictionaryStringValues(IDictionary<string, string[]> dictionary)
+        {
+            var wrapper = dictionary as DictionaryStringArrayWrapper;
+            if (wrapper != null)
+            {
+                return wrapper.Inner;
+            }
+            return new DictionaryStringValuesWrapper(dictionary);
+        }
+
+        internal static IDictionary<string, string[]> MakeDictionaryStringArray(IDictionary<string, StringValues> dictionary)
+        {
+            var wrapper = dictionary as DictionaryStringValuesWrapper;
+            if (wrapper != null)
+            {
+                return wrapper.Inner;
+            }
+            return new DictionaryStringArrayWrapper(dictionary);
+        }
     }
 }

src/Microsoft.AspNet.WebUtilities/FormReader.cs

@@ -8,6 +8,7 @@ using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.Framework.Internal;
+using Microsoft.Framework.Primitives;
 
 namespace Microsoft.AspNet.WebUtilities
 {
@@ -150,11 +151,11 @@ namespace Microsoft.AspNet.WebUtilities
         /// </summary>
         /// <param name="text">The HTTP form body to parse.</param>
         /// <returns>The collection containing the parsed HTTP form body.</returns>
-        public static IDictionary<string, string[]> ReadForm(string text)
+        public static IDictionary<string, StringValues> ReadForm(string text)
         {
             var reader = new FormReader(text);
 
-            var accumulator = new KeyValueAccumulator<string, string>(StringComparer.OrdinalIgnoreCase);
+            var accumulator = new KeyValueAccumulator();
             var pair = reader.ReadNextPair();
             while (pair.HasValue)
             {
@@ -170,7 +171,7 @@ namespace Microsoft.AspNet.WebUtilities
         /// </summary>
         /// <param name="stream">The HTTP form body to parse.</param>
         /// <returns>The collection containing the parsed HTTP form body.</returns>
-        public static Task<IDictionary<string, string[]>> ReadFormAsync(Stream stream, CancellationToken cancellationToken = new CancellationToken())
+        public static Task<IDictionary<string, StringValues>> ReadFormAsync(Stream stream, CancellationToken cancellationToken = new CancellationToken())
         {
             return ReadFormAsync(stream, Encoding.UTF8, cancellationToken);
         }
@@ -180,11 +181,11 @@ namespace Microsoft.AspNet.WebUtilities
         /// </summary>
         /// <param name="stream">The HTTP form body to parse.</param>
         /// <returns>The collection containing the parsed HTTP form body.</returns>
-        public static async Task<IDictionary<string, string[]>> ReadFormAsync(Stream stream, Encoding encoding, CancellationToken cancellationToken = new CancellationToken())
+        public static async Task<IDictionary<string, StringValues>> ReadFormAsync(Stream stream, Encoding encoding, CancellationToken cancellationToken = new CancellationToken())
         {
             var reader = new FormReader(stream, encoding);
 
-            var accumulator = new KeyValueAccumulator<string, string>(StringComparer.OrdinalIgnoreCase);
+            var accumulator = new KeyValueAccumulator();
             var pair = await reader.ReadNextPairAsync(cancellationToken);
             while (pair.HasValue)
             {

src/Microsoft.AspNet.WebUtilities/KeyValueAccumulator.cs

@@ -1,38 +1,37 @@
 // Copyright (c) .NET Foundation. 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 Microsoft.Framework.Internal;
+using Microsoft.Framework.Primitives;
 
 namespace Microsoft.AspNet.WebUtilities
 {
-    public class KeyValueAccumulator<TKey, TValue>
+    public class KeyValueAccumulator
     {
-        private Dictionary<TKey, List<TValue>> _accumulator;
+        private Dictionary<string, List<string>> _accumulator;
-        IEqualityComparer<TKey> _comparer;
 
-        public KeyValueAccumulator([NotNull] IEqualityComparer<TKey> comparer)
+        public KeyValueAccumulator()
         {
-            _comparer = comparer;
+            _accumulator = new Dictionary<string, List<string>>(StringComparer.OrdinalIgnoreCase);
-            _accumulator = new Dictionary<TKey, List<TValue>>(comparer);
         }
 
-        public void Append(TKey key, TValue value)
+        public void Append(string key, string value)
         {
-            List<TValue> values;
+            List<string> values;
             if (_accumulator.TryGetValue(key, out values))
             {
                 values.Add(value);
             }
             else
             {
-                _accumulator[key] = new List<TValue>(1) { value };
+                _accumulator[key] = new List<string>(1) { value };
             }
         }
 
-        public IDictionary<TKey, TValue[]> GetResults()
+        public IDictionary<string, StringValues> GetResults()
         {
-            var results = new Dictionary<TKey, TValue[]>(_comparer);
+            var results = new Dictionary<string, StringValues>(StringComparer.OrdinalIgnoreCase);
             foreach (var kv in _accumulator)
             {
                 results.Add(kv.Key, kv.Value.ToArray());

src/Microsoft.AspNet.WebUtilities/MultipartReader.cs

@@ -8,6 +8,7 @@ using System.IO;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.Framework.Internal;
+using Microsoft.Framework.Primitives;
 
 namespace Microsoft.AspNet.WebUtilities
 {
@@ -64,10 +65,10 @@ namespace Microsoft.AspNet.WebUtilities
             return new MultipartSection() { Headers = headers, Body = _currentStream, BaseStreamOffset = baseStreamOffset };
         }
 
-        private async Task<IDictionary<string, string[]>> ReadHeadersAsync(CancellationToken cancellationToken)
+        private async Task<IDictionary<string, StringValues>> ReadHeadersAsync(CancellationToken cancellationToken)
         {
             int totalSize = 0;
-            var accumulator = new KeyValueAccumulator<string, string>(StringComparer.OrdinalIgnoreCase);
+            var accumulator = new KeyValueAccumulator();
             var line = await _stream.ReadLineAsync(HeaderLengthLimit, cancellationToken);
             while (!string.IsNullOrEmpty(line))
             {

src/Microsoft.AspNet.WebUtilities/MultipartSection.cs

@@ -3,6 +3,7 @@
 
 using System.Collections.Generic;
 using System.IO;
+using Microsoft.Framework.Primitives;
 
 namespace Microsoft.AspNet.WebUtilities
 {
@@ -12,10 +13,10 @@ namespace Microsoft.AspNet.WebUtilities
         {
             get
             {
-                string[] values;
+                StringValues values;
                 if (Headers.TryGetValue("Content-Type", out values))
                 {
-                    return string.Join(", ", values);
+                    return values;
                 }
                 return null;
             }
@@ -25,16 +26,16 @@ namespace Microsoft.AspNet.WebUtilities
         {
             get
             {
-                string[] values;
+                StringValues values;
                 if (Headers.TryGetValue("Content-Disposition", out values))
                 {
-                    return string.Join(", ", values);
+                    return values;
                 }
                 return null;
             }
         }
 
-        public IDictionary<string, string[]> Headers { get; set; }
+        public IDictionary<string, StringValues> Headers { get; set; }
 
         public Stream Body { get; set; }
 

src/Microsoft.AspNet.WebUtilities/QueryHelpers.cs

@@ -5,6 +5,7 @@ using System;
 using System.Collections.Generic;
 using System.Text;
 using Microsoft.Framework.Internal;
+using Microsoft.Framework.Primitives;
 using Microsoft.Framework.WebEncoders;
 
 namespace Microsoft.AspNet.WebUtilities
@@ -72,13 +73,13 @@ namespace Microsoft.AspNet.WebUtilities
         /// </summary>
         /// <param name="text">The raw query string value, with or without the leading '?'.</param>
         /// <returns>A collection of parsed keys and values.</returns>
-        public static IDictionary<string, string[]> ParseQuery(string queryString)
+        public static IDictionary<string, StringValues> ParseQuery(string queryString)
         {
             if (!string.IsNullOrEmpty(queryString) && queryString[0] == '?')
             {
                 queryString = queryString.Substring(1);
             }
-            var accumulator = new KeyValueAccumulator<string, string>(StringComparer.OrdinalIgnoreCase);
+            var accumulator = new KeyValueAccumulator();
 
             int textLength = queryString.Length;
             int equalIndex = queryString.IndexOf('=');

src/Microsoft.AspNet.WebUtilities/project.json

@@ -7,13 +7,13 @@
     },
     "dependencies": {
         "Microsoft.Framework.NotNullAttribute.Sources": { "type": "build", "version": "1.0.0-*" },
+        "Microsoft.Framework.Primitives": "1.0.0-*",
         "Microsoft.Framework.WebEncoders.Core": "1.0.0-*"
     },
     "frameworks": {
         "dnx451": { },
         "dnxcore50": {
             "dependencies": {
-                "System.Collections": "4.0.11-beta-*",
                 "System.Diagnostics.Debug": "4.0.11-beta-*",
                 "System.IO": "4.0.11-beta-*",
                 "System.IO.FileSystem": "4.0.1-beta-*",

src/Microsoft.Framework.Primitives/Microsoft.Framework.Primitives.xproj

@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="14.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <PropertyGroup>
+    <VisualStudioVersion Condition="'$(VisualStudioVersion)' == ''">14.0</VisualStudioVersion>
+    <VSToolsPath Condition="'$(VSToolsPath)' == ''">$(MSBuildExtensionsPath32)\Microsoft\VisualStudio\v$(VisualStudioVersion)</VSToolsPath>
+  </PropertyGroup>
+
+  <Import Project="$(VSToolsPath)\DNX\Microsoft.DNX.Props" Condition="'$(VSToolsPath)' != ''" />
+  <PropertyGroup Label="Globals">
+    <ProjectGuid>e5faccd4-6327-43aa-80a9-ae6f4a3bfe6a</ProjectGuid>
+    <RootNamespace>Microsoft.AspNet.Primitives</RootNamespace>
+    <BaseIntermediateOutputPath Condition="'$(BaseIntermediateOutputPath)'=='' ">..\..\artifacts\obj\$(MSBuildProjectName)</BaseIntermediateOutputPath>
+    <OutputPath Condition="'$(OutputPath)'=='' ">..\..\artifacts\bin\$(MSBuildProjectName)\</OutputPath>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <SchemaVersion>2.0</SchemaVersion>
+  </PropertyGroup>
+  <Import Project="$(VSToolsPath)\DNX\Microsoft.DNX.targets" Condition="'$(VSToolsPath)' != ''" />
+</Project>

src/Microsoft.Framework.Primitives/StringValues.cs

@@ -0,0 +1,233 @@
+// Copyright (c) .NET Foundation. 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;
+
+namespace Microsoft.Framework.Primitives
+{
+    /// <summary>
+    /// Represents zero/null, one, or many strings in an efficient way.
+    /// </summary>
+    public struct StringValues : IList<string>
+    {
+        private static readonly string[] EmptyArray = new string[0];
+        public static readonly StringValues Empty = new StringValues(EmptyArray);
+
+        private readonly string _value;
+        private readonly string[] _values;
+
+        public StringValues(string value)
+        {
+            _value = value;
+            _values = null;
+        }
+
+        public StringValues(string[] values)
+        {
+            _value = null;
+            _values = values;
+        }
+
+        public static implicit operator StringValues(string value)
+        {
+            return new StringValues(value);
+        }
+
+        public static implicit operator StringValues(string[] values)
+        {
+            return new StringValues(values);
+        }
+
+        public static implicit operator string (StringValues values)
+        {
+            return values.GetStringValue();
+        }
+
+        public static implicit operator string[] (StringValues value)
+        {
+            return value.GetArrayValue();
+        }
+
+        public int Count => _values?.Length ?? (_value != null ? 1 : 0);
+
+        bool ICollection<string>.IsReadOnly
+        {
+            get { return true; }
+        }
+
+        string IList<string>.this[int index]
+        {
+            get { return this[index]; }
+            set { throw new NotSupportedException(); }
+        }
+
+        public string this[int key]
+        {
+            get
+            {
+                if (_values != null)
+                {
+                    return _values[key]; // may throw
+                }
+                if (key == 0 && _value != null)
+                {
+                    return _value;
+                }
+                return EmptyArray[0]; // throws
+            }
+        }
+
+        public override string ToString()
+        {
+            return GetStringValue() ?? string.Empty;
+        }
+
+        private string GetStringValue()
+        {
+            if (_values == null)
+            {
+                return _value;
+            }
+            switch (_values.Length)
+            {
+                case 0: return null;
+                case 1: return _values[0];
+                default: return string.Join(",", _values);
+            }
+        }
+
+        public string[] ToArray()
+        {
+            return GetArrayValue() ?? EmptyArray;
+        }
+
+        private string[] GetArrayValue()
+        {
+            if (_value != null)
+            {
+                return new[] { _value };
+            }
+            return _values;
+        }
+
+        int IList<string>.IndexOf(string item)
+        {
+            var index = 0;
+            foreach (var value in this)
+            {
+                if (string.Equals(value, item, StringComparison.Ordinal))
+                {
+                    return index;
+                }
+                index += 1;
+            }
+            return -1;
+        }
+
+        bool ICollection<string>.Contains(string item)
+        {
+            return ((IList<string>)this).IndexOf(item) >= 0;
+        }
+
+        void ICollection<string>.CopyTo(string[] array, int arrayIndex)
+        {
+            for(int i = 0; i < Count; i++)
+            {
+                array[arrayIndex + i] = this[i];
+            }
+        }
+
+        void ICollection<string>.Add(string item)
+        {
+            throw new NotSupportedException();
+        }
+
+        void IList<string>.Insert(int index, string item)
+        {
+            throw new NotSupportedException();
+        }
+
+        bool ICollection<string>.Remove(string item)
+        {
+            throw new NotSupportedException();
+        }
+
+        void IList<string>.RemoveAt(int index)
+        {
+            throw new NotSupportedException();
+        }
+
+        void ICollection<string>.Clear()
+        {
+            throw new NotSupportedException();
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return ((IEnumerable<string>)this).GetEnumerator();
+        }
+
+        IEnumerator<string> IEnumerable<string>.GetEnumerator()
+        {
+            if (Count == 0)
+            {
+                yield break;
+            }
+            if (_values == null)
+            {
+                yield return _value;
+            }
+            else
+            {
+                for (int i = 0; i < _values.Length; i++)
+                {
+                    yield return _values[i];
+                }
+            }
+        }
+
+        public static bool IsNullOrEmpty(StringValues value)
+        {
+            if (value._values == null)
+            {
+                return string.IsNullOrEmpty(value._value);
+            }
+            switch (value._values.Length)
+            {
+                case 0: return true;
+                case 1: return string.IsNullOrEmpty(value._values[0]);
+                default: return false;
+            }
+        }
+
+        public static StringValues Concat(StringValues values1, StringValues values2)
+        {
+            var count1 = values1.Count;
+            var count2 = values2.Count;
+
+            if (count1 == 0)
+            {
+                return values2;
+            }
+
+            if (count2 == 0)
+            {
+                return values1;
+            }
+
+            var combined = new string[count1 + count2];
+            var index = 0;
+            foreach (var value in values1)
+            {
+                combined[index++] = value;
+            }
+            foreach (var value in values2)
+            {
+                combined[index++] = value;
+            }
+            return new StringValues(combined);
+        }
+    }
+}

src/Microsoft.Framework.Primitives/project.json

@@ -0,0 +1,23 @@
+{
+  "version": "1.0.0-*",
+  "description": "Contains primitive types such as StringValues.",
+  "repository": {
+    "type": "git",
+    "url": "git://github.com/aspnet/httpabstractions"
+  },
+  "dependencies": {
+    "Microsoft.Framework.NotNullAttribute.Sources": {
+      "type": "build",
+      "version": "1.0.0-*"
+    }
+  },
+  "frameworks": {
+    "net451": { },
+    "dnx451": { },
+    "dnxcore50": {
+      "dependencies": {
+        "System.Collections": "4.0.11-beta-*"
+      }
+    }
+  }
+}

test/Microsoft.AspNet.Http.Tests/DefaultHttpRequestTests.cs

@@ -5,6 +5,7 @@ using System;
 using System.Collections.Generic;
 using System.Globalization;
 using Microsoft.AspNet.Http.Features;
+using Microsoft.Framework.Primitives;
 using Xunit;
 
 namespace Microsoft.AspNet.Http.Internal
@@ -64,9 +65,9 @@ namespace Microsoft.AspNet.Http.Internal
             // Arrange
             const string expected = "localhost:9001";
 
-            var headers = new Dictionary<string, string[]>(StringComparer.OrdinalIgnoreCase)
+            var headers = new Dictionary<string, StringValues>(StringComparer.OrdinalIgnoreCase)
             {
-                { "Host", new string[] { expected } },
+                { "Host", expected },
             };
 
             var request = CreateRequest(headers);
@@ -84,9 +85,9 @@ namespace Microsoft.AspNet.Http.Internal
             // Arrange
             const string expected = "löcalhöst";
 
-            var headers = new Dictionary<string, string[]>(StringComparer.OrdinalIgnoreCase)
+            var headers = new Dictionary<string, StringValues>(StringComparer.OrdinalIgnoreCase)
             {
-                { "Host", new string[]{ "xn--lcalhst-90ae" } },
+                { "Host", "xn--lcalhst-90ae" },
             };
 
             var request = CreateRequest(headers);
@@ -104,7 +105,7 @@ namespace Microsoft.AspNet.Http.Internal
             // Arrange
             const string expected = "xn--lcalhst-90ae";
 
-            var headers = new Dictionary<string, string[]>(StringComparer.OrdinalIgnoreCase);
+            var headers = new Dictionary<string, StringValues>(StringComparer.OrdinalIgnoreCase);
 
             var request = CreateRequest(headers);
 
@@ -149,9 +150,9 @@ namespace Microsoft.AspNet.Http.Internal
             Assert.Equal("value0", query1["name0"]);
             Assert.Equal("value1", query1["name1"]);
 
-            var query2 = new ReadableStringCollection(new Dictionary<string, string[]>()
+            var query2 = new ReadableStringCollection(new Dictionary<string, StringValues>()
             {
-                { "name2", new[] { "value2" } }
+                { "name2", "value2" }
             });
 
             request.Query = query2;
@@ -164,30 +165,30 @@ namespace Microsoft.AspNet.Http.Internal
         public void Cookies_GetAndSet()
         {
             var request = new DefaultHttpContext().Request;
-            var cookieHeaders = request.Headers.GetValues("Cookie");
+            var cookieHeaders = request.Headers["Cookie"];
-            Assert.Null(cookieHeaders);
+            Assert.Equal(0, cookieHeaders.Count);
             var cookies0 = request.Cookies;
             Assert.Equal(0, cookies0.Count);
 
-            request.Headers.SetValues("Cookie", new[] { "name0=value0", "name1=value1" });
+            request.Headers["Cookie"] = new[] { "name0=value0", "name1=value1" };
             var cookies1 = request.Cookies;
             Assert.Same(cookies0, cookies1);
             Assert.Equal(2, cookies1.Count);
             Assert.Equal("value0", cookies1["name0"]);
             Assert.Equal("value1", cookies1["name1"]);
 
-            var cookies2 = new ReadableStringCollection(new Dictionary<string, string[]>()
+            var cookies2 = new ReadableStringCollection(new Dictionary<string, StringValues>()
             {
-                { "name2", new[] { "value2" } }
+                { "name2", "value2" }
             });
             request.Cookies = cookies2;
             Assert.Same(cookies2, request.Cookies);
             Assert.Equal("value2", request.Cookies["name2"]);
-            cookieHeaders = request.Headers.GetValues("Cookie");
+            cookieHeaders = request.Headers["Cookie"];
             Assert.Equal(new[] { "name2=value2" }, cookieHeaders);
         }
 
-        private static HttpRequest CreateRequest(IDictionary<string, string[]> headers)
+        private static HttpRequest CreateRequest(IDictionary<string, StringValues> headers)
         {
             var context = new DefaultHttpContext();
             context.GetFeature<IHttpRequestFeature>().Headers = headers;
@@ -216,10 +217,10 @@ namespace Microsoft.AspNet.Http.Internal
 
         private static HttpRequest GetRequestWithHeader(string headerName, string headerValue)
         {
-            var headers = new Dictionary<string, string[]>(StringComparer.OrdinalIgnoreCase);
+            var headers = new Dictionary<string, StringValues>(StringComparer.OrdinalIgnoreCase);
             if (headerValue != null)
             {
-                headers.Add(headerName, new[] { headerValue });
+                headers.Add(headerName, headerValue);
             }
 
             return CreateRequest(headers);

test/Microsoft.AspNet.Http.Tests/HeaderDictionaryTests.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using Microsoft.Framework.Primitives;
 using Xunit;
 
 namespace Microsoft.AspNet.Http.Internal
@@ -13,9 +14,9 @@ namespace Microsoft.AspNet.Http.Internal
         public void PropertiesAreAccessible()
         {
             var headers = new HeaderDictionary(
-                new Dictionary<string, string[]>(StringComparer.OrdinalIgnoreCase)
+                new Dictionary<string, StringValues>(StringComparer.OrdinalIgnoreCase)
                 {
-                    { "Header1", new[] { "Value1" } }
+                    { "Header1", "Value1" }
                 });
 
             Assert.Equal(1, headers.Count);
@@ -23,8 +24,7 @@ namespace Microsoft.AspNet.Http.Internal
             Assert.True(headers.ContainsKey("header1"));
             Assert.False(headers.ContainsKey("header2"));
             Assert.Equal("Value1", headers["header1"]);
-            Assert.Equal("Value1", headers.Get("header1"));
+            Assert.Equal(new[] { "Value1" }, headers["header1"].ToArray());
-            Assert.Equal(new[] { "Value1" }, headers.GetValues("header1"));
         }
     }
 }

test/Microsoft.Framework.Primitives.Tests/Microsoft.Framework.Primitives.Tests.xproj

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="14.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <PropertyGroup>
+    <VisualStudioVersion Condition="'$(VisualStudioVersion)' == ''">14.0</VisualStudioVersion>
+    <VSToolsPath Condition="'$(VSToolsPath)' == ''">$(MSBuildExtensionsPath32)\Microsoft\VisualStudio\v$(VisualStudioVersion)</VSToolsPath>
+  </PropertyGroup>
+  <Import Project="$(VSToolsPath)\DNX\Microsoft.DNX.Props" Condition="'$(VSToolsPath)' != ''" />
+  <PropertyGroup Label="Globals">
+    <ProjectGuid>61f72e92-b3ae-4a10-b838-44f80aed40ae</ProjectGuid>
+    <RootNamespace>Microsoft.AspNet.Primitives.Tests</RootNamespace>
+    <BaseIntermediateOutputPath Condition="'$(BaseIntermediateOutputPath)'=='' ">..\..\artifacts\obj\$(MSBuildProjectName)</BaseIntermediateOutputPath>
+    <OutputPath Condition="'$(OutputPath)'=='' ">..\..\artifacts\bin\$(MSBuildProjectName)\</OutputPath>
+  </PropertyGroup>
+  <PropertyGroup>
+    <SchemaVersion>2.0</SchemaVersion>
+  </PropertyGroup>
+  <ItemGroup>
+    <Service Include="{82a7f48d-3b50-4b1e-b82e-3ada8210c358}" />
+  </ItemGroup>
+  <Import Project="$(VSToolsPath)\DNX\Microsoft.DNX.targets" Condition="'$(VSToolsPath)' != ''" />
+</Project>

test/Microsoft.Framework.Primitives.Tests/StringValuesTests.cs

@@ -0,0 +1,117 @@
+// Copyright (c) .NET Foundation. 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.Framework.Primitives
+{
+    public class StringValuesTests
+    {
+        [Fact]
+        public void IsReadOnly_True()
+        {
+            var stringValues = new StringValues();
+            Assert.True(((IList<string>)stringValues).IsReadOnly);
+            Assert.Throws<NotSupportedException>(() => ((IList<string>)stringValues)[0] = string.Empty);
+            Assert.Throws<NotSupportedException>(() => ((ICollection<string>)stringValues).Add(string.Empty));
+            Assert.Throws<NotSupportedException>(() => ((IList<string>)stringValues).Insert(0, string.Empty));
+            Assert.Throws<NotSupportedException>(() => ((ICollection<string>)stringValues).Remove(string.Empty));
+            Assert.Throws<NotSupportedException>(() => ((IList<string>)stringValues).RemoveAt(0));
+            Assert.Throws<NotSupportedException>(() => ((ICollection<string>)stringValues).Clear());
+        }
+
+        [Fact]
+        public void DefaultConstructor_ExpectedValues()
+        {
+            var stringValues = new StringValues();
+            Assert.Equal(0, stringValues.Count);
+            Assert.Equal((string)null, stringValues);
+            Assert.Equal(new string[0], stringValues.ToArray());
+
+            Assert.True(StringValues.IsNullOrEmpty(stringValues));
+            Assert.Throws<IndexOutOfRangeException>(() => stringValues[0]);
+            Assert.Equal(string.Empty, stringValues.ToString());
+            Assert.Equal(-1, ((IList<string>)stringValues).IndexOf(string.Empty));
+            Assert.Equal(0, stringValues.Count());
+        }
+
+        [Fact]
+        public void Constructor_NullStringValue_ExpectedValues()
+        {
+            var stringValues = new StringValues((string)null);
+            Assert.Equal(0, stringValues.Count);
+            Assert.Null((string)stringValues);
+            Assert.Equal(string.Empty, stringValues.ToString());
+            Assert.Null((string[])stringValues);
+            Assert.Equal(new string[0], stringValues.ToArray());
+
+            Assert.True(StringValues.IsNullOrEmpty(stringValues));
+            Assert.Throws<IndexOutOfRangeException>(() => stringValues[0]);
+            Assert.Equal(-1, ((IList<string>)stringValues).IndexOf(string.Empty));
+            Assert.Equal(0, stringValues.Count());
+        }
+
+        [Fact]
+        public void Constructor_NullStringArray_ExpectedValues()
+        {
+            var stringValues = new StringValues((string[])null);
+            Assert.Equal(0, stringValues.Count);
+            Assert.Null((string)stringValues);
+            Assert.Equal(string.Empty, stringValues.ToString());
+            Assert.Null((string[])stringValues);
+            Assert.Equal(new string[0], stringValues.ToArray());
+
+            Assert.True(StringValues.IsNullOrEmpty(stringValues));
+            Assert.Throws<IndexOutOfRangeException>(() => stringValues[0]);
+            Assert.Equal(string.Empty, stringValues.ToString());
+            Assert.Equal(-1, ((IList<string>)stringValues).IndexOf(string.Empty));
+            Assert.Equal(0, stringValues.Count());
+        }
+
+        [Fact]
+        public void ImplicitStringConverter_Works()
+        {
+            string nullString = null;
+            StringValues stringValues = nullString;
+            Assert.Equal(0, stringValues.Count);
+            Assert.Null((string)stringValues);
+            Assert.Null((string[])stringValues);
+
+            string aString = "abc";
+            stringValues = aString;
+            Assert.Equal(1, stringValues.Count);
+            Assert.Equal(aString, stringValues);
+            Assert.Equal(aString, stringValues[0]);
+            Assert.Equal<string[]>(new string[] { aString }, stringValues);
+        }
+
+        [Fact]
+        public void ImplicitStringArrayConverter_Works()
+        {
+            string[] nullStringArray = null;
+            StringValues stringValues = nullStringArray;
+            Assert.Equal(0, stringValues.Count);
+            Assert.Null((string)stringValues);
+            Assert.Null((string[])stringValues);
+
+            string aString = "abc";
+            string[] aStringArray = new[] { aString };
+            stringValues = aStringArray;
+            Assert.Equal(1, stringValues.Count);
+            Assert.Equal(aString, stringValues);
+            Assert.Equal(aString, stringValues[0]);
+            Assert.Equal<string[]>(aStringArray, stringValues);
+
+            aString = "abc";
+            string bString = "bcd";
+            aStringArray = new[] { aString, bString };
+            stringValues = aStringArray;
+            Assert.Equal(2, stringValues.Count);
+            Assert.Equal("abc,bcd", stringValues);
+            Assert.Equal<string[]>(aStringArray, stringValues);
+        }
+    }
+}

test/Microsoft.Framework.Primitives.Tests/project.json

@@ -0,0 +1,13 @@
+{
+  "dependencies": {
+    "Microsoft.Framework.Primitives": "1.0.0-*",
+    "xunit.runner.aspnet": "2.0.0-aspnet-*"
+  },
+  "commands": {
+    "test": "xunit.runner.aspnet"
+  },
+  "frameworks": {
+    "dnx451": { },
+    "dnxcore50": { }
+  }
+}