diff --git a/src/Microsoft.AspNet.Mvc.Core/CreatedAtActionResult.cs b/src/Microsoft.AspNet.Mvc.Core/CreatedAtActionResult.cs
index 2e1c5c7aba..709d6b2558 100644
--- a/src/Microsoft.AspNet.Mvc.Core/CreatedAtActionResult.cs
+++ b/src/Microsoft.AspNet.Mvc.Core/CreatedAtActionResult.cs
@@ -7,6 +7,7 @@
 using Microsoft.AspNet.Mvc.Core;
 using Microsoft.Framework.DependencyInjection;
 using Microsoft.Framework.Internal;
+using Microsoft.Net.Http.Headers;
 
 namespace Microsoft.AspNet.Mvc
 {
@@ -73,7 +74,7 @@ protected override void OnFormatting([NotNull] ActionContext context)
                 throw new InvalidOperationException(Resources.NoRoutesMatched);
             }
 
-            context.HttpContext.Response.Headers.Set("Location", url);
+            context.HttpContext.Response.Headers[HeaderNames.Location] = url;
         }
     }
 }
\ No newline at end of file
diff --git a/src/Microsoft.AspNet.Mvc.Core/CreatedAtRouteResult.cs b/src/Microsoft.AspNet.Mvc.Core/CreatedAtRouteResult.cs
index 1767fed7bf..5131136bf1 100644
--- a/src/Microsoft.AspNet.Mvc.Core/CreatedAtRouteResult.cs
+++ b/src/Microsoft.AspNet.Mvc.Core/CreatedAtRouteResult.cs
@@ -7,6 +7,7 @@
 using Microsoft.AspNet.Mvc.Core;
 using Microsoft.Framework.DependencyInjection;
 using Microsoft.Framework.Internal;
+using Microsoft.Net.Http.Headers;
 
 namespace Microsoft.AspNet.Mvc
 {
@@ -70,7 +71,7 @@ protected override void OnFormatting([NotNull] ActionContext context)
                 throw new InvalidOperationException(Resources.NoRoutesMatched);
             }
 
-            context.HttpContext.Response.Headers.Set("Location", url);
+            context.HttpContext.Response.Headers[HeaderNames.Location] = url;
         }
     }
 }
\ No newline at end of file
diff --git a/src/Microsoft.AspNet.Mvc.Core/CreatedResult.cs b/src/Microsoft.AspNet.Mvc.Core/CreatedResult.cs
index 31801556ed..af7148657f 100644
--- a/src/Microsoft.AspNet.Mvc.Core/CreatedResult.cs
+++ b/src/Microsoft.AspNet.Mvc.Core/CreatedResult.cs
@@ -4,6 +4,7 @@
 using System;
 using Microsoft.AspNet.Http;
 using Microsoft.Framework.Internal;
+using Microsoft.Net.Http.Headers;
 
 namespace Microsoft.AspNet.Mvc
 {
@@ -50,7 +51,7 @@ public string Location
         /// <inheritdoc />
         protected override void OnFormatting([NotNull] ActionContext context)
         {
-            context.HttpContext.Response.Headers.Set("Location", Location);
+            context.HttpContext.Response.Headers[HeaderNames.Location] = Location;
         }
     }
 }
\ No newline at end of file
diff --git a/src/Microsoft.AspNet.Mvc.Core/FileResult.cs b/src/Microsoft.AspNet.Mvc.Core/FileResult.cs
index 814be3e544..d33ce318c4 100644
--- a/src/Microsoft.AspNet.Mvc.Core/FileResult.cs
+++ b/src/Microsoft.AspNet.Mvc.Core/FileResult.cs
@@ -68,7 +68,7 @@ public override Task ExecuteResultAsync([NotNull] ActionContext context)
                 // basis for the actual filename, where possible.
                 var cd = new ContentDispositionHeaderValue("attachment");
                 cd.SetHttpFileName(FileDownloadName);
-                context.HttpContext.Response.Headers.Set(HeaderNames.ContentDisposition, cd.ToString());
+                context.HttpContext.Response.Headers[HeaderNames.ContentDisposition] = cd.ToString();
             }
 
             // We aren't flowing the cancellation token appropriately, see
diff --git a/src/Microsoft.AspNet.Mvc.Core/HttpMethodConstraint.cs b/src/Microsoft.AspNet.Mvc.Core/HttpMethodConstraint.cs
index edabe282c8..be65914c9a 100644
--- a/src/Microsoft.AspNet.Mvc.Core/HttpMethodConstraint.cs
+++ b/src/Microsoft.AspNet.Mvc.Core/HttpMethodConstraint.cs
@@ -5,6 +5,7 @@
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.Linq;
+using Microsoft.AspNet.Primitives;
 using Microsoft.Framework.Internal;
 
 namespace Microsoft.AspNet.Mvc
@@ -62,12 +63,12 @@ public bool Accept([NotNull] ActionConstraintContext context)
             if (request.Headers.ContainsKey(OriginHeader))
             {
                 // Update the http method if it is preflight request.
-                var accessControlRequestMethod = request.Headers.Get(AccessControlRequestMethod);
+                var accessControlRequestMethod = request.Headers[AccessControlRequestMethod];
                 if (string.Equals(
                         request.Method,
                         PreflightHttpMethod,
                         StringComparison.Ordinal) &&
-                    accessControlRequestMethod != null)
+                    !StringValues.IsNullOrEmpty(accessControlRequestMethod))
                 {
                     method = accessControlRequestMethod;
                 }
diff --git a/src/Microsoft.AspNet.Mvc.Core/ModelBinding/FormCollectionModelBinder.cs b/src/Microsoft.AspNet.Mvc.Core/ModelBinding/FormCollectionModelBinder.cs
index de3cbf4061..431cd1329b 100644
--- a/src/Microsoft.AspNet.Mvc.Core/ModelBinding/FormCollectionModelBinder.cs
+++ b/src/Microsoft.AspNet.Mvc.Core/ModelBinding/FormCollectionModelBinder.cs
@@ -7,6 +7,7 @@
 using System.Threading.Tasks;
 using Microsoft.AspNet.Http;
 using Microsoft.AspNet.Http.Internal;
+using Microsoft.AspNet.Primitives;
 using Microsoft.Framework.Internal;
 
 namespace Microsoft.AspNet.Mvc.ModelBinding
@@ -42,7 +43,7 @@ public async Task<ModelBindingResult> BindModelAsync([NotNull] ModelBindingConte
             }
             else
             {
-                model = new FormCollection(new Dictionary<string, string[]>());
+                model = new FormCollection(new Dictionary<string, StringValues>());
             }
 
             var validationNode =
diff --git a/src/Microsoft.AspNet.Mvc.Core/ModelBinding/HeaderModelBinder.cs b/src/Microsoft.AspNet.Mvc.Core/ModelBinding/HeaderModelBinder.cs
index 2a253ece64..9061ad5848 100644
--- a/src/Microsoft.AspNet.Mvc.Core/ModelBinding/HeaderModelBinder.cs
+++ b/src/Microsoft.AspNet.Mvc.Core/ModelBinding/HeaderModelBinder.cs
@@ -7,6 +7,7 @@
 using System.Reflection;
 #endif
 using System.Threading.Tasks;
+using Microsoft.AspNet.Primitives;
 using Microsoft.Framework.Internal;
 
 namespace Microsoft.AspNet.Mvc.ModelBinding
@@ -36,7 +37,7 @@ protected override Task<ModelBindingResult> BindModelCoreAsync([NotNull] ModelBi
             object model = null;
             if (bindingContext.ModelType == typeof(string))
             {
-                var value = request.Headers.Get(headerName);
+                string value = request.Headers[headerName];
                 if (value != null)
                 {
                     model = value;
@@ -45,7 +46,7 @@ protected override Task<ModelBindingResult> BindModelCoreAsync([NotNull] ModelBi
             else if (typeof(IEnumerable<string>).IsAssignableFrom(bindingContext.ModelType))
             {
                 var values = request.Headers.GetCommaSeparatedValues(headerName);
-                if (values != null)
+                if (values.Count > 0)
                 {
                     model = ModelBindingHelper.ConvertValuesToCollectionType(
                         bindingContext.ModelType,
@@ -61,7 +62,7 @@ protected override Task<ModelBindingResult> BindModelCoreAsync([NotNull] ModelBi
                     bindingContext.ModelMetadata,
                     model);
 
-                var attemptedValue = (model as string) ?? request.Headers.Get(headerName);
+                var attemptedValue = (model as string) ?? request.Headers[headerName];
                 var valueProviderResult = new ValueProviderResult(model, attemptedValue, CultureInfo.InvariantCulture);
                 bindingContext.ModelState.SetModelValue(bindingContext.ModelName, valueProviderResult);
             }
diff --git a/src/Microsoft.AspNet.Mvc.Core/ModelBinding/JQueryFormValueProvider.cs b/src/Microsoft.AspNet.Mvc.Core/ModelBinding/JQueryFormValueProvider.cs
index e1e319dd95..6ea03df260 100644
--- a/src/Microsoft.AspNet.Mvc.Core/ModelBinding/JQueryFormValueProvider.cs
+++ b/src/Microsoft.AspNet.Mvc.Core/ModelBinding/JQueryFormValueProvider.cs
@@ -6,6 +6,7 @@
 using System.Diagnostics;
 using System.Globalization;
 using System.Threading.Tasks;
+using Microsoft.AspNet.Primitives;
 using Microsoft.Framework.Internal;
 
 namespace Microsoft.AspNet.Mvc.ModelBinding
@@ -16,10 +17,10 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
     /// </summary>
     public class JQueryFormValueProvider : BindingSourceValueProvider, IEnumerableValueProvider
     {
-        private readonly Func<Task<IDictionary<string, string[]>>> _valuesFactory;
+        private readonly Func<Task<IDictionary<string, StringValues>>> _valuesFactory;
 
         private PrefixContainer _prefixContainer;
-        private IDictionary<string, string[]> _values;
+        private IDictionary<string, StringValues> _values;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="DictionaryBasedValueProvider"/> class.
@@ -29,7 +30,7 @@ public class JQueryFormValueProvider : BindingSourceValueProvider, IEnumerableVa
         /// <param name="culture">The culture to return with ValueProviderResult instances.</param>
         public JQueryFormValueProvider(
             [NotNull] BindingSource bindingSource,
-            [NotNull] Func<Task<IDictionary<string, string[]>>> valuesFactory,
+            [NotNull] Func<Task<IDictionary<string, StringValues>>> valuesFactory,
             CultureInfo culture)
             : base(bindingSource)
         {
@@ -40,7 +41,7 @@ public JQueryFormValueProvider(
         // Internal for testing.
         internal JQueryFormValueProvider(
             [NotNull] BindingSource bindingSource,
-            [NotNull] IDictionary<string, string[]> values,
+            [NotNull] IDictionary<string, StringValues> values,
             CultureInfo culture)
             : base(bindingSource)
         {
@@ -70,22 +71,26 @@ public override async Task<ValueProviderResult> GetValueAsync(string key)
         {
             var dictionary = await GetDictionary();
 
-            string[] values;
-            if (dictionary.TryGetValue(key, out values) && values != null && values.Length > 0)
+            StringValues values;
+            if (dictionary.TryGetValue(key, out values) && values.Count > 0)
             {
-                // Success.
-                if (values.Length == 1)
+                if (values.Count == 1)
                 {
-                    return new ValueProviderResult(values[0], values[0], Culture);
+                    var value = (string)values;
+                    return new ValueProviderResult(value, value, Culture);
+                }
+                else
+                {
+                    var rawValue = (string[])values;
+                    var value = (string)values;
+                    return new ValueProviderResult(rawValue, value, Culture);
                 }
-
-                return new ValueProviderResult(values, string.Join(",", values), Culture);
             }
 
             return null;
         }
 
-        private async Task<IDictionary<string, string[]>> GetDictionary()
+        private async Task<IDictionary<string, StringValues>> GetDictionary()
         {
             if (_values == null)
             {
diff --git a/src/Microsoft.AspNet.Mvc.Core/ModelBinding/JQueryFormValueProviderFactory.cs b/src/Microsoft.AspNet.Mvc.Core/ModelBinding/JQueryFormValueProviderFactory.cs
index e40cd205c0..3b7052a636 100644
--- a/src/Microsoft.AspNet.Mvc.Core/ModelBinding/JQueryFormValueProviderFactory.cs
+++ b/src/Microsoft.AspNet.Mvc.Core/ModelBinding/JQueryFormValueProviderFactory.cs
@@ -8,6 +8,7 @@
 using System.Threading.Tasks;
 using Microsoft.AspNet.Http;
 using Microsoft.AspNet.Mvc.Core;
+using Microsoft.AspNet.Primitives;
 using Microsoft.Framework.Internal;
 
 namespace Microsoft.AspNet.Mvc.ModelBinding
@@ -29,11 +30,11 @@ public IValueProvider GetValueProvider([NotNull] ValueProviderFactoryContext con
             return null;
         }
 
-        private static async Task<IDictionary<string, string[]>> GetValueCollectionAsync(HttpRequest request)
+        private static async Task<IDictionary<string, StringValues>> GetValueCollectionAsync(HttpRequest request)
         {
             var formCollection = await request.ReadFormAsync();
 
-            var dictionary = new Dictionary<string, string[]>(StringComparer.OrdinalIgnoreCase);
+            var dictionary = new Dictionary<string, StringValues>(StringComparer.OrdinalIgnoreCase);
             foreach (var entry in formCollection)
             {
                 var key = NormalizeJQueryToMvc(entry.Key);
diff --git a/src/Microsoft.AspNet.Mvc.Core/ModelBinding/ReadableStringCollectionValueProvider.cs b/src/Microsoft.AspNet.Mvc.Core/ModelBinding/ReadableStringCollectionValueProvider.cs
index 346617eea9..32a23dc639 100644
--- a/src/Microsoft.AspNet.Mvc.Core/ModelBinding/ReadableStringCollectionValueProvider.cs
+++ b/src/Microsoft.AspNet.Mvc.Core/ModelBinding/ReadableStringCollectionValueProvider.cs
@@ -7,6 +7,7 @@
 using System.Globalization;
 using System.Threading.Tasks;
 using Microsoft.AspNet.Http;
+using Microsoft.AspNet.Primitives;
 using Microsoft.Framework.Internal;
 
 namespace Microsoft.AspNet.Mvc.ModelBinding
@@ -80,21 +81,21 @@ public virtual async Task<IDictionary<string, string>> GetKeysFromPrefixAsync([N
         public override async Task<ValueProviderResult> GetValueAsync([NotNull] string key)
         {
             var collection = await GetValueCollectionAsync();
-            var values = collection.GetValues(key);
+            var values = collection[key];
 
             ValueProviderResult result;
-            if (values == null)
+            if (values.Count == 0)
             {
                 result = null;
             }
             else if (values.Count == 1)
             {
-                var value = (string)values[0];
+                var value = (string)values;
                 result = new ValueProviderResult(value, value, _culture);
             }
             else
             {
-                result = new ValueProviderResult(values, _values.Get(key), _culture);
+                result = new ValueProviderResult((string[])values, _values[key], _culture);
             }
 
             return result;
diff --git a/src/Microsoft.AspNet.Mvc.Core/ResponseCacheFilter.cs b/src/Microsoft.AspNet.Mvc.Core/ResponseCacheFilter.cs
index ebe249a72b..988b820c39 100644
--- a/src/Microsoft.AspNet.Mvc.Core/ResponseCacheFilter.cs
+++ b/src/Microsoft.AspNet.Mvc.Core/ResponseCacheFilter.cs
@@ -6,6 +6,7 @@
 using System.Linq;
 using Microsoft.AspNet.Mvc.Core;
 using Microsoft.Framework.Internal;
+using Microsoft.Net.Http.Headers;
 
 namespace Microsoft.AspNet.Mvc
 {
@@ -94,24 +95,24 @@ public void OnActionExecuting([NotNull] ActionExecutingContext context)
             var headers = context.HttpContext.Response.Headers;
 
             // Clear all headers
-            headers.Remove("Vary");
-            headers.Remove("Cache-control");
-            headers.Remove("Pragma");
+            headers.Remove(HeaderNames.Vary);
+            headers.Remove(HeaderNames.CacheControl);
+            headers.Remove(HeaderNames.Pragma);
 
             if (!string.IsNullOrEmpty(VaryByHeader))
             {
-                headers.Set("Vary", VaryByHeader);
+                headers[HeaderNames.Vary] = VaryByHeader;
             }
 
             if (NoStore)
             {
-                headers.Set("Cache-control", "no-store");
+                headers[HeaderNames.CacheControl] = "no-store";
 
                 // Cache-control: no-store, no-cache is valid.
                 if (Location == ResponseCacheLocation.None)
                 {
-                    headers.Append("Cache-control", "no-cache");
-                    headers.Set("Pragma", "no-cache");
+                    headers.AppendCommaSeparatedValues(HeaderNames.CacheControl, "no-cache");
+                    headers[HeaderNames.Pragma] = "no-cache";
                 }
             }
             else
@@ -127,7 +128,7 @@ public void OnActionExecuting([NotNull] ActionExecutingContext context)
                         break;
                     case ResponseCacheLocation.None:
                         cacheControlValue = "no-cache";
-                        headers.Set("Pragma", "no-cache");
+                        headers[HeaderNames.Pragma] = "no-cache";
                         break;
                 }
 
@@ -140,7 +141,7 @@ public void OnActionExecuting([NotNull] ActionExecutingContext context)
 
                 if (cacheControlValue != null)
                 {
-                    headers.Set("Cache-control", cacheControlValue);
+                    headers[HeaderNames.CacheControl] = cacheControlValue;
                 }
             }
         }
diff --git a/src/Microsoft.AspNet.Mvc.Cors/CorsAuthorizationFilter.cs b/src/Microsoft.AspNet.Mvc.Cors/CorsAuthorizationFilter.cs
index bc07ef6373..e12b6268fb 100644
--- a/src/Microsoft.AspNet.Mvc.Cors/CorsAuthorizationFilter.cs
+++ b/src/Microsoft.AspNet.Mvc.Cors/CorsAuthorizationFilter.cs
@@ -7,6 +7,7 @@
 using System.Threading.Tasks;
 using Microsoft.AspNet.Cors.Core;
 using Microsoft.AspNet.Http;
+using Microsoft.AspNet.Primitives;
 using Microsoft.Framework.Internal;
 
 namespace Microsoft.AspNet.Mvc
@@ -63,12 +64,12 @@ public async Task OnAuthorizationAsync([NotNull] AuthorizationContext context)
                 _corsService.ApplyResult(result, context.HttpContext.Response);
 
                 var accessControlRequestMethod = 
-                        httpContext.Request.Headers.Get(CorsConstants.AccessControlRequestMethod);
+                        httpContext.Request.Headers[CorsConstants.AccessControlRequestMethod];
                 if (string.Equals(
                         request.Method,
                         CorsConstants.PreflightHttpMethod,
                         StringComparison.Ordinal) &&
-                    accessControlRequestMethod != null)
+                    !StringValues.IsNullOrEmpty(accessControlRequestMethod))
                 {
                     // If this was a preflight, there is no need to run anything else.
                     // Also the response is always 200 so that anyone after mvc can handle the pre flight request.
diff --git a/src/Microsoft.AspNet.Mvc.Cors/DisableCorsAuthorizationFilter.cs b/src/Microsoft.AspNet.Mvc.Cors/DisableCorsAuthorizationFilter.cs
index 4885d622f5..2ec9d48f3c 100644
--- a/src/Microsoft.AspNet.Mvc.Cors/DisableCorsAuthorizationFilter.cs
+++ b/src/Microsoft.AspNet.Mvc.Cors/DisableCorsAuthorizationFilter.cs
@@ -5,6 +5,7 @@
 using System.Threading.Tasks;
 using Microsoft.AspNet.Cors.Core;
 using Microsoft.AspNet.Http;
+using Microsoft.AspNet.Primitives;
 using Microsoft.Framework.Internal;
 
 namespace Microsoft.AspNet.Mvc
@@ -27,12 +28,12 @@ public int Order
         public Task OnAuthorizationAsync([NotNull] AuthorizationContext context)
         {
             var accessControlRequestMethod = 
-                        context.HttpContext.Request.Headers.Get(CorsConstants.AccessControlRequestMethod);
+                        context.HttpContext.Request.Headers[CorsConstants.AccessControlRequestMethod];
             if (string.Equals(
                     context.HttpContext.Request.Method,
                     CorsConstants.PreflightHttpMethod,
                     StringComparison.Ordinal) &&
-                accessControlRequestMethod != null)
+                !StringValues.IsNullOrEmpty(accessControlRequestMethod))
             {
                 // Short circuit if the request is preflight as that should not result in action execution.
                 context.Result = new HttpStatusCodeResult(StatusCodes.Status200OK);
diff --git a/src/Microsoft.AspNet.Mvc.WebApiCompatShim/Formatters/HttpResponseMessageOutputFormatter.cs b/src/Microsoft.AspNet.Mvc.WebApiCompatShim/Formatters/HttpResponseMessageOutputFormatter.cs
index ce6f977a51..e09fa19669 100644
--- a/src/Microsoft.AspNet.Mvc.WebApiCompatShim/Formatters/HttpResponseMessageOutputFormatter.cs
+++ b/src/Microsoft.AspNet.Mvc.WebApiCompatShim/Formatters/HttpResponseMessageOutputFormatter.cs
@@ -53,7 +53,7 @@ public async Task WriteAsync(OutputFormatterContext context)
                 
                 foreach (var header in responseHeaders)
                 {
-                    response.Headers.AppendValues(header.Key, header.Value.ToArray());
+                    response.Headers.Append(header.Key, header.Value.ToArray());
                 }
 
                 if (responseMessage.Content != null)
@@ -67,7 +67,7 @@ public async Task WriteAsync(OutputFormatterContext context)
                     
                     foreach (var header in contentHeaders)
                     {
-                        response.Headers.AppendValues(header.Key, header.Value.ToArray());
+                        response.Headers.Append(header.Key, header.Value.ToArray());
                     }
 
                     await responseMessage.Content.CopyToAsync(response.Body);
diff --git a/src/Microsoft.AspNet.Mvc.WebApiCompatShim/HttpRequestMessage/HttpRequestMessageFeature.cs b/src/Microsoft.AspNet.Mvc.WebApiCompatShim/HttpRequestMessage/HttpRequestMessageFeature.cs
index a0c2ae056b..0af8ba7221 100644
--- a/src/Microsoft.AspNet.Mvc.WebApiCompatShim/HttpRequestMessage/HttpRequestMessageFeature.cs
+++ b/src/Microsoft.AspNet.Mvc.WebApiCompatShim/HttpRequestMessage/HttpRequestMessageFeature.cs
@@ -1,6 +1,7 @@
 // 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.Generic;
 using System.Diagnostics;
 using System.Net.Http;
 using Microsoft.AspNet.Http;
@@ -58,9 +59,9 @@ private static HttpRequestMessage CreateHttpRequestMessage(HttpContext httpConte
             {
                 // Every header should be able to fit into one of the two header collections.
                 // Try message.Headers first since that accepts more of them.
-                if (!message.Headers.TryAddWithoutValidation(header.Key, header.Value))
+                if (!message.Headers.TryAddWithoutValidation(header.Key, (IEnumerable<string>)header.Value))
                 {
-                    var added = message.Content.Headers.TryAddWithoutValidation(header.Key, header.Value);
+                    var added = message.Content.Headers.TryAddWithoutValidation(header.Key, (IEnumerable<string>)header.Value);
                     Debug.Assert(added);
                 }
             }
diff --git a/test/Microsoft.AspNet.Mvc.Core.Test/CreatedAtActionResultTests.cs b/test/Microsoft.AspNet.Mvc.Core.Test/CreatedAtActionResultTests.cs
index 5d2da109ac..4c3736a536 100644
--- a/test/Microsoft.AspNet.Mvc.Core.Test/CreatedAtActionResultTests.cs
+++ b/test/Microsoft.AspNet.Mvc.Core.Test/CreatedAtActionResultTests.cs
@@ -70,7 +70,7 @@ private static HttpResponse GetMockedHttpResponseObject()
             var httpResponse = new Mock<HttpResponse>();
             httpResponse.SetupProperty(o => o.StatusCode);
             httpResponse.Setup(o => o.Headers).Returns(
-                new HeaderDictionary(new Dictionary<string, string[]>()));
+                new HeaderDictionary());
             httpResponse.SetupGet(o => o.Body).Returns(stream);
             return httpResponse.Object;
         }
diff --git a/test/Microsoft.AspNet.Mvc.Core.Test/CreatedResultTests.cs b/test/Microsoft.AspNet.Mvc.Core.Test/CreatedResultTests.cs
index 7b556a8838..49d31674eb 100644
--- a/test/Microsoft.AspNet.Mvc.Core.Test/CreatedResultTests.cs
+++ b/test/Microsoft.AspNet.Mvc.Core.Test/CreatedResultTests.cs
@@ -53,7 +53,7 @@ public async Task CreatedResult_OverwritesLocationHeader()
             var location = "/test/";
             var httpContext = GetHttpContext();
             var actionContext = GetActionContext(httpContext);
-            httpContext.Response.Headers.Set("Location", "/different/location/");
+            httpContext.Response.Headers["Location"] = "/different/location/";
             var result = new CreatedResult(location, "testInput");
 
             // Act
diff --git a/test/Microsoft.AspNet.Mvc.Core.Test/FormatFilterTest.cs b/test/Microsoft.AspNet.Mvc.Core.Test/FormatFilterTest.cs
index 5f855d6c3a..0ade1df1b3 100644
--- a/test/Microsoft.AspNet.Mvc.Core.Test/FormatFilterTest.cs
+++ b/test/Microsoft.AspNet.Mvc.Core.Test/FormatFilterTest.cs
@@ -72,7 +72,7 @@ public void FormatFilter_ContextContainsFormat_InRouteAndQueryData()
 
             // Query contains xml    
             httpContext.Setup(c => c.Request.Query.ContainsKey("format")).Returns(true);
-            httpContext.Setup(c => c.Request.Query.Get("format")).Returns("xml");
+            httpContext.Setup(c => c.Request.Query["format"]).Returns("xml");
 
             // Routedata contains json
             var data = new RouteData();
diff --git a/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/CompositeValueProviderTest.cs b/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/CompositeValueProviderTest.cs
index 6537336403..40a1f7fa87 100644
--- a/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/CompositeValueProviderTest.cs
+++ b/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/CompositeValueProviderTest.cs
@@ -8,6 +8,7 @@
 using System.Globalization;
 #if DNX451
 using System.Threading.Tasks;
+using Microsoft.AspNet.Primitives;
 using Moq;
 using Xunit;
 #endif
@@ -18,11 +19,11 @@ public class CompositeValueProviderTest : EnumerableValueProviderTest
     {
         protected override IEnumerableValueProvider GetEnumerableValueProvider(
             BindingSource bindingSource,
-            IDictionary<string, string[]> values,
+            IDictionary<string, StringValues> values,
             CultureInfo culture)
         {
             var emptyValueProvider =
-                new JQueryFormValueProvider(bindingSource, new Dictionary<string, string[]>(), culture);
+                new JQueryFormValueProvider(bindingSource, new Dictionary<string, StringValues>(), culture);
             var valueProvider = new JQueryFormValueProvider(bindingSource, values, culture);
 
             return new CompositeValueProvider(new[] { emptyValueProvider, valueProvider });
diff --git a/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/DictionaryModelBinderTest.cs b/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/DictionaryModelBinderTest.cs
index 617bd67337..9ebc8c58fc 100644
--- a/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/DictionaryModelBinderTest.cs
+++ b/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/DictionaryModelBinderTest.cs
@@ -8,6 +8,7 @@
 using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.AspNet.Http.Internal;
+using Microsoft.AspNet.Primitives;
 using Moq;
 using Xunit;
 
@@ -442,10 +443,10 @@ private static IValueProvider CreateEnumerableValueProvider(
             string keyFormat,
             IDictionary<string, string> dictionary)
         {
-            // Convert to an IDictionary<string, string[]> then wrap it up.
+            // Convert to an IDictionary<string, StringValues> then wrap it up.
             var backingStore = dictionary.ToDictionary(
                 kvp => string.Format(keyFormat, kvp.Key),
-                kvp => new[] { kvp.Value });
+                kvp => (StringValues)kvp.Value);
             var stringCollection = new ReadableStringCollection(backingStore);
 
             return new ReadableStringCollectionValueProvider(
diff --git a/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/EnumerableValueProviderTest.cs b/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/EnumerableValueProviderTest.cs
index 9fdaf664f6..d816c9f39f 100644
--- a/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/EnumerableValueProviderTest.cs
+++ b/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/EnumerableValueProviderTest.cs
@@ -5,34 +5,35 @@
 using System.Globalization;
 using System.Linq;
 using System.Threading.Tasks;
+using Microsoft.AspNet.Primitives;
 using Xunit;
 
 namespace Microsoft.AspNet.Mvc.ModelBinding
 {
     public abstract class EnumerableValueProviderTest
     {
-        private static readonly IDictionary<string, string[]> _backingStore = new Dictionary<string, string[]>
+        private static readonly IDictionary<string, StringValues> _backingStore = new Dictionary<string, StringValues>
         {
             { "some", new[] { "someValue1", "someValue2" } },
-            { "null_value", null },
+            { "null_value", StringValues.Empty },
             { "prefix.name", new[] { "someOtherValue" } },
-            { "prefix.null_value", null },
-            { "prefix.property1.property", null },
-            { "prefix.property2[index]", null },
-            { "prefix[index1]", null },
-            { "prefix[index1].property1", null },
-            { "prefix[index1].property2", null },
-            { "prefix[index2].property", null },
-            { "[index]", null },
-            { "[index].property", null },
-            { "[index][anotherIndex]", null },
+            { "prefix.null_value", StringValues.Empty },
+            { "prefix.property1.property", StringValues.Empty },
+            { "prefix.property2[index]", StringValues.Empty },
+            { "prefix[index1]", StringValues.Empty },
+            { "prefix[index1].property1", StringValues.Empty },
+            { "prefix[index1].property2", StringValues.Empty },
+            { "prefix[index2].property", StringValues.Empty },
+            { "[index]", StringValues.Empty },
+            { "[index].property", StringValues.Empty },
+            { "[index][anotherIndex]", StringValues.Empty },
         };
 
         [Fact]
         public async Task ContainsPrefixAsync_WithEmptyCollection_ReturnsFalseForEmptyPrefix()
         {
             // Arrange
-            var backingStore = new Dictionary<string, string[]>();
+            var backingStore = new Dictionary<string, StringValues>();
             var valueProvider = GetEnumerableValueProvider(BindingSource.Query, backingStore, culture: null);
 
             // Act
@@ -184,7 +185,7 @@ public async Task GetValueAsync_MultiValue()
 
             // Assert
             Assert.NotNull(result);
-            Assert.Equal(new[] { "someValue1", "someValue2" }, (IList<string>)result.RawValue);
+            Assert.Equal(new[] { "someValue1", "someValue2" }, result.RawValue);
             Assert.Equal("someValue1,someValue2", result.AttemptedValue);
             Assert.Equal(culture, result.Culture);
         }
@@ -209,7 +210,7 @@ public async Task GetValue_NullValue(string key)
         public async Task GetValueAsync_NullMultipleValue()
         {
             // Arrange
-            var backingStore = new Dictionary<string, string[]>
+            var backingStore = new Dictionary<string, StringValues>
             {
                 { "key", new string[] { null, null, "value" } },
             };
@@ -278,7 +279,7 @@ public void FilterExclude()
 
         private IBindingSourceValueProvider GetBindingSourceValueProvider(
             BindingSource bindingSource,
-            IDictionary<string, string[]> values,
+            IDictionary<string, StringValues> values,
             CultureInfo culture)
         {
             var provider = GetEnumerableValueProvider(bindingSource, values, culture) as IBindingSourceValueProvider;
@@ -291,7 +292,7 @@ private IBindingSourceValueProvider GetBindingSourceValueProvider(
 
         protected abstract IEnumerableValueProvider GetEnumerableValueProvider(
             BindingSource bindingSource,
-            IDictionary<string, string[]> values,
+            IDictionary<string, StringValues> values,
             CultureInfo culture);
     }
 }
diff --git a/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/FormCollectionModelBinderTest.cs b/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/FormCollectionModelBinderTest.cs
index 9e6216a9e1..124e5d2dc9 100644
--- a/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/FormCollectionModelBinderTest.cs
+++ b/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/FormCollectionModelBinderTest.cs
@@ -9,6 +9,7 @@
 using System.Threading.Tasks;
 using Microsoft.AspNet.Http;
 using Microsoft.AspNet.Http.Internal;
+using Microsoft.AspNet.Primitives;
 using Moq;
 using Xunit;
 
@@ -20,10 +21,10 @@ public class FormCollectionModelBinderTest
         public async Task FormCollectionModelBinder_ValidType_BindSuccessful()
         {
             // Arrange
-            var formCollection = new FormCollection(new Dictionary<string, string[]>
+            var formCollection = new FormCollection(new Dictionary<string, StringValues>
             {
-                { "field1", new string[] { "value1" } },
-                { "field2", new string[] { "value2" } }
+                { "field1", "value1" },
+                { "field2", "value2" }
             });
             var httpContext = GetMockHttpContext(formCollection);
             var bindingContext = GetBindingContext(typeof(FormCollection), httpContext);
@@ -48,10 +49,10 @@ public async Task FormCollectionModelBinder_ValidType_BindSuccessful()
         public async Task FormCollectionModelBinder_InvalidType_BindFails()
         {
             // Arrange
-            var formCollection = new FormCollection(new Dictionary<string, string[]>
+            var formCollection = new FormCollection(new Dictionary<string, StringValues>
             {
-                { "field1", new string[] { "value1" } },
-                { "field2", new string[] { "value2" } }
+                { "field1", "value1" },
+                { "field2", "value2" }
             });
             var httpContext = GetMockHttpContext(formCollection);
             var bindingContext = GetBindingContext(typeof(string), httpContext);
@@ -85,10 +86,10 @@ public async Task FormCollectionModelBinder_NoForm_BindSuccessful_ReturnsEmptyFo
         public async Task FormCollectionModelBinder_CustomFormCollection_BindSuccessful()
         {
             // Arrange
-            var formCollection = new MyFormCollection(new Dictionary<string, string[]>
+            var formCollection = new MyFormCollection(new Dictionary<string, StringValues>
             {
-                { "field1", new string[] { "value1" } },
-                { "field2", new string[] { "value2" } }
+                { "field1", "value1" },
+                { "field2", "value2" }
             });
             var httpContext = GetMockHttpContext(formCollection);
             var bindingContext = GetBindingContext(typeof(FormCollection), httpContext);
@@ -134,11 +135,11 @@ private static ModelBindingContext GetBindingContext(Type modelType, HttpContext
 
         private class MyFormCollection : ReadableStringCollection, IFormCollection
         {
-            public MyFormCollection(IDictionary<string, string[]> store) : this(store, new FormFileCollection())
+            public MyFormCollection(IDictionary<string, StringValues> store) : this(store, new FormFileCollection())
             {
             }
 
-            public MyFormCollection(IDictionary<string, string[]> store, IFormFileCollection files) : base(store)
+            public MyFormCollection(IDictionary<string, StringValues> store, IFormFileCollection files) : base(store)
             {
                 Files = files;
             }
diff --git a/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/JQueryFormValueProviderFactoryTest.cs b/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/JQueryFormValueProviderFactoryTest.cs
index c95b2691d5..179f1bf956 100644
--- a/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/JQueryFormValueProviderFactoryTest.cs
+++ b/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/JQueryFormValueProviderFactoryTest.cs
@@ -6,13 +6,14 @@
 using System.Globalization;
 using System.Threading.Tasks;
 using Microsoft.AspNet.Http.Internal;
+using Microsoft.AspNet.Primitives;
 using Xunit;
 
 namespace Microsoft.AspNet.Mvc.ModelBinding.Test
 {
     public class JQueryFormValueProviderFactoryTest
     {
-        private static readonly IDictionary<string, string[]> _backingStore = new Dictionary<string, string[]>
+        private static readonly IDictionary<string, StringValues> _backingStore = new Dictionary<string, StringValues>
         {
             { "[]", new[] { "found" } },
             { "[]property1", new[] { "found" } },
@@ -118,7 +119,7 @@ public async Task GetValueProvider_ReturnsValueProvider_ContainingExpectedKeys(s
 
         private static ValueProviderFactoryContext CreateContext(
             string contentType,
-            IDictionary<string, string[]> formValues)
+            IDictionary<string, StringValues> formValues)
         {
             var context = new DefaultHttpContext();
             context.Request.ContentType = contentType;
diff --git a/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/JQueryFormValueProviderTest.cs b/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/JQueryFormValueProviderTest.cs
index 4fa1b91d66..1d2aef6e3f 100644
--- a/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/JQueryFormValueProviderTest.cs
+++ b/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/JQueryFormValueProviderTest.cs
@@ -3,6 +3,7 @@
 
 using System.Collections.Generic;
 using System.Globalization;
+using Microsoft.AspNet.Primitives;
 
 namespace Microsoft.AspNet.Mvc.ModelBinding
 {
@@ -10,7 +11,7 @@ public class JQueryFormValueProviderTest : EnumerableValueProviderTest
     {
         protected override IEnumerableValueProvider GetEnumerableValueProvider(
             BindingSource bindingSource,
-            IDictionary<string, string[]> values,
+            IDictionary<string, StringValues> values,
             CultureInfo culture)
         {
             return new JQueryFormValueProvider(bindingSource, values, culture);
diff --git a/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/ReadableStringCollectionValueProviderTest.cs b/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/ReadableStringCollectionValueProviderTest.cs
index 9a3cd94490..7785496d70 100644
--- a/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/ReadableStringCollectionValueProviderTest.cs
+++ b/test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/ReadableStringCollectionValueProviderTest.cs
@@ -4,6 +4,7 @@
 using System.Collections.Generic;
 using System.Globalization;
 using Microsoft.AspNet.Http.Internal;
+using Microsoft.AspNet.Primitives;
 
 namespace Microsoft.AspNet.Mvc.ModelBinding
 {
@@ -11,7 +12,7 @@ public class ReadableStringCollectionValueProviderTest : EnumerableValueProvider
     {
         protected override IEnumerableValueProvider GetEnumerableValueProvider(
             BindingSource bindingSource,
-            IDictionary<string, string[]> values,
+            IDictionary<string, StringValues> values,
             CultureInfo culture)
         {
             var backingStore = new ReadableStringCollection(values);
diff --git a/test/Microsoft.AspNet.Mvc.Core.Test/ResponseCacheFilterTest.cs b/test/Microsoft.AspNet.Mvc.Core.Test/ResponseCacheFilterTest.cs
index 347ada991b..6e758e98a4 100644
--- a/test/Microsoft.AspNet.Mvc.Core.Test/ResponseCacheFilterTest.cs
+++ b/test/Microsoft.AspNet.Mvc.Core.Test/ResponseCacheFilterTest.cs
@@ -27,7 +27,7 @@ public void ResponseCacheFilter_DoesNotThrow_WhenNoStoreIsTrue()
             cache.OnActionExecuting(context);
 
             // Assert
-            Assert.Equal("no-store", context.HttpContext.Response.Headers.Get("Cache-control"));
+            Assert.Equal("no-store", context.HttpContext.Response.Headers["Cache-control"]);
         }
 
         [Fact]
@@ -157,7 +157,7 @@ public void OnActionExecuting_CanSetCacheControlHeaders(ResponseCacheFilter cach
             cache.OnActionExecuting(context);
 
             // Assert
-            Assert.Equal(output, context.HttpContext.Response.Headers.Get("Cache-control"));
+            Assert.Equal(output, context.HttpContext.Response.Headers["Cache-control"]);
         }
 
         public static IEnumerable<object[]> NoStoreData
@@ -205,7 +205,7 @@ public void OnActionExecuting_DoesNotSetLocationOrDuration_IfNoStoreIsSet(
             cache.OnActionExecuting(context);
 
             // Assert
-            Assert.Equal(output, context.HttpContext.Response.Headers.Get("Cache-control"));
+            Assert.Equal(output, context.HttpContext.Response.Headers["Cache-control"]);
         }
 
         public static IEnumerable<object[]> VaryData
@@ -275,8 +275,8 @@ public void ResponseCacheCanSetVary(ResponseCacheFilter cache, string varyOutput
             cache.OnActionExecuting(context);
 
             // Assert
-            Assert.Equal(varyOutput, context.HttpContext.Response.Headers.Get("Vary"));
-            Assert.Equal(cacheControlOutput, context.HttpContext.Response.Headers.Get("Cache-control"));
+            Assert.Equal(varyOutput, context.HttpContext.Response.Headers["Vary"]);
+            Assert.Equal(cacheControlOutput, context.HttpContext.Response.Headers["Cache-control"]);
         }
 
         [Fact]
@@ -294,8 +294,8 @@ public void SetsPragmaOnNoCache()
             cache.OnActionExecuting(context);
 
             // Assert
-            Assert.Equal("no-store,no-cache", context.HttpContext.Response.Headers.Get("Cache-control"));
-            Assert.Equal("no-cache", context.HttpContext.Response.Headers.Get("Pragma"));
+            Assert.Equal("no-store,no-cache", context.HttpContext.Response.Headers["Cache-control"]);
+            Assert.Equal("no-cache", context.HttpContext.Response.Headers["Pragma"]);
         }
 
         [Fact]
@@ -339,7 +339,7 @@ public void FilterDurationProperty_OverridesCachePolicySetting()
             cache.OnActionExecuting(context);
 
             // Assert
-            Assert.Equal("public,max-age=20", context.HttpContext.Response.Headers.Get("Cache-control"));
+            Assert.Equal("public,max-age=20", context.HttpContext.Response.Headers["Cache-control"]);
         }
 
         [Fact]
@@ -359,7 +359,7 @@ public void FilterLocationProperty_OverridesCachePolicySetting()
             cache.OnActionExecuting(context);
 
             // Assert
-            Assert.Equal("private,max-age=10", context.HttpContext.Response.Headers.Get("Cache-control"));
+            Assert.Equal("private,max-age=10", context.HttpContext.Response.Headers["Cache-control"]);
         }
 
         [Fact]
@@ -379,7 +379,7 @@ public void FilterNoStoreProperty_OverridesCachePolicySetting()
             cache.OnActionExecuting(context);
 
             // Assert
-            Assert.Equal("public,max-age=10", context.HttpContext.Response.Headers.Get("Cache-control"));
+            Assert.Equal("public,max-age=10", context.HttpContext.Response.Headers["Cache-control"]);
         }
 
         [Fact]
@@ -399,7 +399,7 @@ public void FilterVaryByProperty_OverridesCachePolicySetting()
             cache.OnActionExecuting(context);
 
             // Assert
-            Assert.Equal("Test", context.HttpContext.Response.Headers.Get("Vary"));
+            Assert.Equal("Test", context.HttpContext.Response.Headers["Vary"]);
         }
 
         private ActionExecutingContext GetActionExecutingContext(List<IFilterMetadata> filters = null)
diff --git a/test/Microsoft.AspNet.Mvc.Cors.Test/CorsAuthorizationFilterTest.cs b/test/Microsoft.AspNet.Mvc.Cors.Test/CorsAuthorizationFilterTest.cs
index 1fbadf4168..34fae4fec6 100644
--- a/test/Microsoft.AspNet.Mvc.Cors.Test/CorsAuthorizationFilterTest.cs
+++ b/test/Microsoft.AspNet.Mvc.Cors.Test/CorsAuthorizationFilterTest.cs
@@ -186,10 +186,9 @@ private ICorsService GetPassingEngine(bool supportsCredentials = false)
                 .Callback<CorsResult, HttpResponse>((result1, response1) =>
                 {
                     var headers = response1.Headers;
-                    headers.Set(
-                        CorsConstants.AccessControlMaxAge,
-                        result1.PreflightMaxAge.Value.TotalSeconds.ToString());
-                    headers.Add(CorsConstants.AccessControlAllowOrigin, new[] { result1.AllowedOrigin });
+                    headers[CorsConstants.AccessControlMaxAge] =
+                        result1.PreflightMaxAge.Value.TotalSeconds.ToString();
+                    headers[CorsConstants.AccessControlAllowOrigin] = result1.AllowedOrigin;
                     if (result1.SupportsCredentials)
                     {
                         headers.Add(CorsConstants.AccessControlAllowCredentials, new[] { "true" });
diff --git a/test/Microsoft.AspNet.Mvc.Formatters.Xml.Test/XmlDataContractSerializerOutputFormatterTest.cs b/test/Microsoft.AspNet.Mvc.Formatters.Xml.Test/XmlDataContractSerializerOutputFormatterTest.cs
index 9a4dff1ce6..cca8b2273e 100644
--- a/test/Microsoft.AspNet.Mvc.Formatters.Xml.Test/XmlDataContractSerializerOutputFormatterTest.cs
+++ b/test/Microsoft.AspNet.Mvc.Formatters.Xml.Test/XmlDataContractSerializerOutputFormatterTest.cs
@@ -621,7 +621,7 @@ private static HttpContext GetHttpContext(string contentType)
         {
             var request = new Mock<HttpRequest>();
 
-            var headers = new HeaderDictionary(new Dictionary<string, string[]>(StringComparer.OrdinalIgnoreCase));
+            var headers = new HeaderDictionary();
             headers["Accept-Charset"] = MediaTypeHeaderValue.Parse(contentType).Charset;
             request.Setup(r => r.ContentType).Returns(contentType);
             request.SetupGet(r => r.Headers).Returns(headers);
diff --git a/test/Microsoft.AspNet.Mvc.Formatters.Xml.Test/XmlSerializerOutputFormatterTest.cs b/test/Microsoft.AspNet.Mvc.Formatters.Xml.Test/XmlSerializerOutputFormatterTest.cs
index 873ad1da0a..cb4e3e9304 100644
--- a/test/Microsoft.AspNet.Mvc.Formatters.Xml.Test/XmlSerializerOutputFormatterTest.cs
+++ b/test/Microsoft.AspNet.Mvc.Formatters.Xml.Test/XmlSerializerOutputFormatterTest.cs
@@ -375,7 +375,7 @@ private static HttpContext GetHttpContext(string contentType)
         {
             var request = new Mock<HttpRequest>();
 
-            var headers = new HeaderDictionary(new Dictionary<string, string[]>(StringComparer.OrdinalIgnoreCase));
+            var headers = new HeaderDictionary();
             headers["Accept-Charset"] = MediaTypeHeaderValue.Parse(contentType).Charset;
             request.Setup(r => r.ContentType).Returns(contentType);
             request.SetupGet(r => r.Headers).Returns(headers);
diff --git a/test/Microsoft.AspNet.Mvc.FunctionalTests/FiltersTest.cs b/test/Microsoft.AspNet.Mvc.FunctionalTests/FiltersTest.cs
index b24c1e3949..f105f20cf7 100644
--- a/test/Microsoft.AspNet.Mvc.FunctionalTests/FiltersTest.cs
+++ b/test/Microsoft.AspNet.Mvc.FunctionalTests/FiltersTest.cs
@@ -68,12 +68,12 @@ public async Task ListAllFilters()
 
             var body = await response.Content.ReadAsStringAsync();
 
-            var filters = response.Headers.GetValues("filters").Single().Split(',');
+            var filters = response.Headers.GetValues("filters").ToArray();
 
             var i = 0;
             foreach (var filter in filters)
             {
-                Assert.Equal(filter, expected[i++]);
+                Assert.Equal(expected[i++], filter);
             }
 
             Assert.Equal(expected.Length, filters.Length);
diff --git a/test/Microsoft.AspNet.Mvc.IntegrationTests/CollectionModelBinderIntegrationTest.cs b/test/Microsoft.AspNet.Mvc.IntegrationTests/CollectionModelBinderIntegrationTest.cs
index 1037f03c09..bfecbf4c20 100644
--- a/test/Microsoft.AspNet.Mvc.IntegrationTests/CollectionModelBinderIntegrationTest.cs
+++ b/test/Microsoft.AspNet.Mvc.IntegrationTests/CollectionModelBinderIntegrationTest.cs
@@ -9,6 +9,7 @@
 using Microsoft.AspNet.Http;
 using Microsoft.AspNet.Http.Internal;
 using Microsoft.AspNet.Mvc.ModelBinding;
+using Microsoft.AspNet.Primitives;
 using Xunit;
 
 namespace Microsoft.AspNet.Mvc.IntegrationTests
@@ -570,7 +571,7 @@ public async Task CollectionModelBinder_UsesCustomIndexes()
 
             var operationContext = ModelBindingTestHelper.GetOperationBindingContext(request =>
             {
-                var formCollection = new FormCollection(new Dictionary<string, string[]>()
+                var formCollection = new FormCollection(new Dictionary<string, StringValues>()
                 {
                     { "Addresses.index", new [] { "Key1", "Key2" } },
                     { "Addresses[Key1].Street", new [] { "Street1" } },
@@ -629,7 +630,7 @@ public async Task CollectionModelBinder_UsesCustomIndexes_AddsErrorsWithCorrectK
 
             var operationContext = ModelBindingTestHelper.GetOperationBindingContext(request =>
             {
-                var formCollection = new FormCollection(new Dictionary<string, string[]>()
+                var formCollection = new FormCollection(new Dictionary<string, StringValues>()
                 {
                     { "Addresses.index", new [] { "Key1" } },
                     { "Addresses[Key1].Street", new [] { "Street1" } },
diff --git a/test/Microsoft.AspNet.Mvc.IntegrationTests/FormCollectionModelBindingIntegrationTest.cs b/test/Microsoft.AspNet.Mvc.IntegrationTests/FormCollectionModelBindingIntegrationTest.cs
index b6d10783d1..9e28dadc88 100644
--- a/test/Microsoft.AspNet.Mvc.IntegrationTests/FormCollectionModelBindingIntegrationTest.cs
+++ b/test/Microsoft.AspNet.Mvc.IntegrationTests/FormCollectionModelBindingIntegrationTest.cs
@@ -9,6 +9,7 @@
 using Microsoft.AspNet.Http.Features.Internal;
 using Microsoft.AspNet.Http.Internal;
 using Microsoft.AspNet.Mvc.ModelBinding;
+using Microsoft.AspNet.Primitives;
 using Xunit;
 
 namespace Microsoft.AspNet.Mvc.IntegrationTests
@@ -163,7 +164,7 @@ public async Task BindParameter_NoData_BindsWithEmptyCollection()
         private void UpdateRequest(HttpRequest request, string data, string name)
         {
             var fileCollection = new FormFileCollection();
-            var formCollection = new FormCollection(new Dictionary<string, string[]>(), fileCollection);
+            var formCollection = new FormCollection(new Dictionary<string, StringValues>(), fileCollection);
             var memoryStream = new MemoryStream(Encoding.UTF8.GetBytes(data));
 
             request.Form = formCollection;
diff --git a/test/Microsoft.AspNet.Mvc.IntegrationTests/FormFileModelBindingIntegrationTest.cs b/test/Microsoft.AspNet.Mvc.IntegrationTests/FormFileModelBindingIntegrationTest.cs
index 89c21c0ed2..573d9f35c8 100644
--- a/test/Microsoft.AspNet.Mvc.IntegrationTests/FormFileModelBindingIntegrationTest.cs
+++ b/test/Microsoft.AspNet.Mvc.IntegrationTests/FormFileModelBindingIntegrationTest.cs
@@ -9,6 +9,7 @@
 using Microsoft.AspNet.Http.Features.Internal;
 using Microsoft.AspNet.Http.Internal;
 using Microsoft.AspNet.Mvc.ModelBinding;
+using Microsoft.AspNet.Primitives;
 using Xunit;
 
 namespace Microsoft.AspNet.Mvc.IntegrationTests
@@ -164,7 +165,7 @@ public async Task BindParameter_NoData_DoesNotGetBound()
         private void UpdateRequest(HttpRequest request, string data, string name)
         {
             var fileCollection = new FormFileCollection();
-            var formCollection = new FormCollection(new Dictionary<string, string[]>(), fileCollection);
+            var formCollection = new FormCollection(new Dictionary<string, StringValues>(), fileCollection);
 
             request.Form = formCollection;
             request.ContentType = "multipart/form-data; boundary=----WebKitFormBoundarymx2fSWqWSd0OxQqq";
diff --git a/test/Microsoft.AspNet.Mvc.IntegrationTests/MutableObjectModelBinderIntegrationTest.cs b/test/Microsoft.AspNet.Mvc.IntegrationTests/MutableObjectModelBinderIntegrationTest.cs
index d3f709ec4c..b5a5e3af5d 100644
--- a/test/Microsoft.AspNet.Mvc.IntegrationTests/MutableObjectModelBinderIntegrationTest.cs
+++ b/test/Microsoft.AspNet.Mvc.IntegrationTests/MutableObjectModelBinderIntegrationTest.cs
@@ -10,6 +10,7 @@
 using Microsoft.AspNet.Http.Features.Internal;
 using Microsoft.AspNet.Http.Internal;
 using Microsoft.AspNet.Mvc.ModelBinding;
+using Microsoft.AspNet.Primitives;
 using Xunit;
 
 namespace Microsoft.AspNet.Mvc.IntegrationTests
@@ -2127,7 +2128,7 @@ private static void SetJsonBodyContent(HttpRequest request, string content)
         private static void SetFormFileBodyContent(HttpRequest request, string content, string name)
         {
             var fileCollection = new FormFileCollection();
-            var formCollection = new FormCollection(new Dictionary<string, string[]>(), fileCollection);
+            var formCollection = new FormCollection(new Dictionary<string, StringValues>(), fileCollection);
             var memoryStream = new MemoryStream(Encoding.UTF8.GetBytes(content));
 
             request.Form = formCollection;
diff --git a/test/Microsoft.AspNet.Mvc.IntegrationTests/TypeConverterModelBinderIntegrationTest.cs b/test/Microsoft.AspNet.Mvc.IntegrationTests/TypeConverterModelBinderIntegrationTest.cs
index 3b87dbbd12..8c1273a77a 100644
--- a/test/Microsoft.AspNet.Mvc.IntegrationTests/TypeConverterModelBinderIntegrationTest.cs
+++ b/test/Microsoft.AspNet.Mvc.IntegrationTests/TypeConverterModelBinderIntegrationTest.cs
@@ -9,6 +9,7 @@
 using Microsoft.AspNet.Http;
 using Microsoft.AspNet.Http.Internal;
 using Microsoft.AspNet.Mvc.ModelBinding;
+using Microsoft.AspNet.Primitives;
 using Xunit;
 
 namespace Microsoft.AspNet.Mvc.IntegrationTests
@@ -328,19 +329,19 @@ public async Task BindParameter_NoData_DoesNotGetBound()
             Assert.Empty(modelState.Keys);
         }
 
-        public static TheoryData<IDictionary<string, string[]>> PersonStoreData
+        public static TheoryData<IDictionary<string, StringValues>> PersonStoreData
         {
             get
             {
-                return new TheoryData<IDictionary<string, string[]>>
+                return new TheoryData<IDictionary<string, StringValues>>
                 {
-                    new Dictionary<string, string[]>
+                    new Dictionary<string, StringValues>
                     {
                         { "name", new[] { "Fred" } },
                         { "address.zip", new[] { "98052" } },
                         { "address.lines", new[] { "line 1", "line 2" } },
                     },
-                    new Dictionary<string, string[]>
+                    new Dictionary<string, StringValues>
                     {
                         { "address.lines[]", new[] { "line 1", "line 2" } },
                         { "address[].zip", new[] { "98052" } },
@@ -352,7 +353,7 @@ public static TheoryData<IDictionary<string, string[]>> PersonStoreData
 
         [Theory]
         [MemberData(nameof(PersonStoreData))]
-        public async Task BindParameter_FromFormData_BindsCorrectly(IDictionary<string, string[]> personStore)
+        public async Task BindParameter_FromFormData_BindsCorrectly(IDictionary<string, StringValues> personStore)
         {
             // Arrange
             var argumentBinder = ModelBindingTestHelper.GetArgumentBinder();
diff --git a/test/Microsoft.AspNet.Mvc.WebApiCompatShimTest/HttpResponseMessageOutputFormatterTests.cs b/test/Microsoft.AspNet.Mvc.WebApiCompatShimTest/HttpResponseMessageOutputFormatterTests.cs
index eafd06a84a..2a7a6b712e 100644
--- a/test/Microsoft.AspNet.Mvc.WebApiCompatShimTest/HttpResponseMessageOutputFormatterTests.cs
+++ b/test/Microsoft.AspNet.Mvc.WebApiCompatShimTest/HttpResponseMessageOutputFormatterTests.cs
@@ -113,7 +113,7 @@ public async Task ExplicitlySet_MultipleEncodings_ChunkedNotIgnored()
             // Assert
             Assert.True(httpContext.Response.Headers.ContainsKey(transferEncodingHeaderKey));
             Assert.Equal(new string[] { "identity", "chunked" }, 
-                        httpContext.Response.Headers.GetValues(transferEncodingHeaderKey));
+                        httpContext.Response.Headers[transferEncodingHeaderKey]);
             Assert.NotNull(httpContext.Response.ContentLength);
         }
 
@@ -141,7 +141,7 @@ public async Task ExplicitlySet_MultipleEncodingsUsingChunkedFlag_ChunkedNotIgno
             // Assert
             Assert.True(httpContext.Response.Headers.ContainsKey(transferEncodingHeaderKey));
             Assert.Equal(new string[] { "identity", "chunked" },
-                        httpContext.Response.Headers.GetValues(transferEncodingHeaderKey));
+                        httpContext.Response.Headers[transferEncodingHeaderKey]);
             Assert.NotNull(httpContext.Response.ContentLength);
         }
 
diff --git a/test/WebSites/CustomRouteWebSite/LocalizedRoute.cs b/test/WebSites/CustomRouteWebSite/LocalizedRoute.cs
index 443742ceab..82eba00ccc 100644
--- a/test/WebSites/CustomRouteWebSite/LocalizedRoute.cs
+++ b/test/WebSites/CustomRouteWebSite/LocalizedRoute.cs
@@ -63,7 +63,7 @@ public async Task RouteAsync(RouteContext context)
         private string GetLocale(HttpContext context)
         {
             string locale;
-            _users.TryGetValue(context.Request.Headers.Get("User"), out locale);
+            _users.TryGetValue(context.Request.Headers["User"], out locale);
             return locale;
         }
     }
diff --git a/test/WebSites/LoggingWebSite/Models/RequestInfoDto.cs b/test/WebSites/LoggingWebSite/Models/RequestInfoDto.cs
index a51224ba03..79066880f8 100644
--- a/test/WebSites/LoggingWebSite/Models/RequestInfoDto.cs
+++ b/test/WebSites/LoggingWebSite/Models/RequestInfoDto.cs
@@ -1,6 +1,5 @@
-using System;
-using System.Collections.Generic;
-using Microsoft.AspNet.Http;
+using System.Collections.Generic;
+using Microsoft.AspNet.Primitives;
 
 namespace LoggingWebSite
 {
@@ -22,10 +21,10 @@ public class RequestInfoDto
 
         public string Protocol { get; set; }
 
-        public IEnumerable<KeyValuePair<string, string[]>> Headers { get; set; }
+        public IEnumerable<KeyValuePair<string, StringValues>> Headers { get; set; }
 
         public string Query { get; set; }
 
-        public IEnumerable<KeyValuePair<string, string[]>> Cookies { get; set; }
+        public IEnumerable<KeyValuePair<string, StringValues>> Cookies { get; set; }
     }
 }
\ No newline at end of file
diff --git a/test/WebSites/ModelBindingWebSite/Controllers/ModelBinderAttribute_ProductController.cs b/test/WebSites/ModelBindingWebSite/Controllers/ModelBinderAttribute_ProductController.cs
index 55c6418589..fd1520eaf4 100644
--- a/test/WebSites/ModelBindingWebSite/Controllers/ModelBinderAttribute_ProductController.cs
+++ b/test/WebSites/ModelBindingWebSite/Controllers/ModelBinderAttribute_ProductController.cs
@@ -73,7 +73,7 @@ public Task<ModelBindingResult> BindModelAsync(ModelBindingContext bindingContex
                     // Doing something slightly different here to make sure we don't get accidentally bound
                     // by the type converter binder.
                     OrderStatus model;
-                    var isModelSet = Enum.TryParse<OrderStatus>("Status" + request.Query.Get("status"), out model);
+                    var isModelSet = Enum.TryParse<OrderStatus>("Status" + request.Query["status"], out model);
                     var validationNode =
                      new ModelValidationNode(bindingContext.ModelName, bindingContext.ModelMetadata, model);
                     return Task.FromResult(new ModelBindingResult(model, "status", isModelSet, validationNode));
diff --git a/test/WebSites/ModelBindingWebSite/Controllers/TryUpdateModelController.cs b/test/WebSites/ModelBindingWebSite/Controllers/TryUpdateModelController.cs
index 7c8d5c0c3f..d42c767e0a 100644
--- a/test/WebSites/ModelBindingWebSite/Controllers/TryUpdateModelController.cs
+++ b/test/WebSites/ModelBindingWebSite/Controllers/TryUpdateModelController.cs
@@ -10,6 +10,7 @@
 using Microsoft.AspNet.Http.Internal;
 using Microsoft.AspNet.Mvc;
 using Microsoft.AspNet.Mvc.ModelBinding;
+using Microsoft.AspNet.Primitives;
 using ModelBindingWebSite.Models;
 
 namespace ModelBindingWebSite.Controllers
@@ -107,7 +108,7 @@ public async Task<User> GetUserAsync_WithChainedProperties(int id)
         public async Task<Employee> GetEmployeeAsync_BindToBaseDeclaredType()
         {
             var backingStore = new ReadableStringCollection(
-            new Dictionary<string, string[]>
+            new Dictionary<string, StringValues>
             {
                 { "Parent.Name", new[] { "fatherName"} },
                 { "Parent.Parent.Name", new[] {"grandFatherName" } },
@@ -131,7 +132,7 @@ await TryUpdateModelAsync(
         public async Task<User> GetUserAsync_ModelType_IncludeAll(int id)
         {
             var backingStore = new ReadableStringCollection(
-            new Dictionary<string, string[]>
+            new Dictionary<string, StringValues>
             {
                 { "Key", new[] { "123"} },
                 { "RegisterationMonth", new[] {"March" } },
diff --git a/test/WebSites/ResponseCacheWebSite/Controllers/CacheHeadersController.cs b/test/WebSites/ResponseCacheWebSite/Controllers/CacheHeadersController.cs
index d7fb644928..87b8267da5 100644
--- a/test/WebSites/ResponseCacheWebSite/Controllers/CacheHeadersController.cs
+++ b/test/WebSites/ResponseCacheWebSite/Controllers/CacheHeadersController.cs
@@ -46,7 +46,7 @@ public IActionResult NoCacheAtAll()
         [ResponseCache(Duration = 40)]
         public IActionResult SetHeadersInAction()
         {
-            Response.Headers.Set("Cache-control", "max-age=10");
+            Response.Headers["Cache-control"] = "max-age=10";
             return Content("Hello World!");
         }
 
diff --git a/test/WebSites/VersioningWebSite/VersionRangeValidator.cs b/test/WebSites/VersioningWebSite/VersionRangeValidator.cs
index fef545c84b..7d6c01e1bf 100644
--- a/test/WebSites/VersioningWebSite/VersionRangeValidator.cs
+++ b/test/WebSites/VersioningWebSite/VersionRangeValidator.cs
@@ -21,7 +21,7 @@ public VersionRangeValidator(int? minVersion, int? maxVersion)
 
         public static string GetVersion(HttpRequest request)
         {
-            return request.Query.Get("version");
+            return request.Query["version"];
         }
 
         public bool Accept(ActionConstraintContext context)