Allow _ViewImports to remove default inherited tag helpers.

Additionally simplifying the contract for
ChunkInheritaceUtility\IChunkMerger so we don't have to understand the
order in which CodeTrees appear.

src/Microsoft.AspNet.Mvc.Razor.Host/Directives/ChunkHelper.cs

@@ -3,7 +3,6 @@
 
 using System;
 using System.Linq;
-using Microsoft.AspNet.Mvc.Razor.Host;
 using Microsoft.AspNet.Razor.Chunks;
 
 namespace Microsoft.AspNet.Mvc.Razor.Directives
@@ -15,33 +14,6 @@ namespace Microsoft.AspNet.Mvc.Razor.Directives
     {
         private const string TModelToken = "<TModel>";
 
-        /// <summary>
-        /// Attempts to cast the passed in <see cref="Chunk"/> to type <typeparamref name="TChunk"/> and throws if the
-        /// cast fails.
-        /// </summary>
-        /// <typeparam name="TChunk">The type to cast to.</typeparam>
-        /// <param name="chunk">The chunk to cast.</param>
-        /// <returns>The <paramref name="chunk"/> cast to <typeparamref name="TChunk"/>.</returns>
-        /// <exception cref="ArgumentException"><paramref name="chunk"/> is not an instance of
-        /// <typeparamref name="TChunk"/>.</exception>
-        public static TChunk EnsureChunk<TChunk>(Chunk chunk)
-            where TChunk : Chunk
-        {
-            if (chunk == null)
-            {
-                throw new ArgumentNullException(nameof(chunk));
-            }
-
-            var chunkOfT = chunk as TChunk;
-            if (chunkOfT == null)
-            {
-                var message = Resources.FormatArgumentMustBeOfType(typeof(TChunk).FullName);
-                throw new ArgumentException(message, nameof(chunk));
-            }
-
-            return chunkOfT;
-        }
-
         /// <summary>
         /// Returns the <see cref="ModelChunk"/> used to determine the model name for the page generated
         /// using the specified <paramref name="chunkTree"/>

src/Microsoft.AspNet.Mvc.Razor.Host/Directives/ChunkInheritanceUtility.cs

@@ -63,6 +63,12 @@ namespace Microsoft.AspNet.Mvc.Razor.Directives
         /// <param name="pagePath">The path of the page to locate inherited chunks for.</param>
         /// <returns>A <see cref="IReadOnlyList{ChunkTreeResult}"/> of parsed <c>_ViewImports</c>
         /// <see cref="ChunkTree"/>s and their file paths.</returns>
+        /// <remarks>
+        /// The resulting <see cref="IReadOnlyList{ChunkTreeResult}"/> is ordered so that the result
+        /// for a _ViewImport closest to the application root appears first and the _ViewImport
+        /// closest to the page appears last i.e.
+        /// [ /_ViewImport, /Views/_ViewImport, /Views/Home/_ViewImport ]
+        /// </remarks>
         public virtual IReadOnlyList<ChunkTreeResult> GetInheritedChunkTreeResults(string pagePath)
         {
             if (pagePath == null)
@@ -88,7 +94,7 @@ namespace Microsoft.AspNet.Mvc.Razor.Directives
                 if (chunkTree != null)
                 {
                     var result = new ChunkTreeResult(chunkTree, viewImportsPath);
-                    inheritedChunkTreeResults.Add(result);
+                    inheritedChunkTreeResults.Insert(0, result);
                 }
             }
 
@@ -102,7 +108,7 @@ namespace Microsoft.AspNet.Mvc.Razor.Directives
         /// <param name="chunkTree">The <see cref="ChunkTree"/> to merge in to.</param>
         /// <param name="inheritedChunkTrees"><see cref="IReadOnlyList{ChunkTree}"/> inherited from <c>_ViewImports</c>
         /// files.</param>
-        /// <param name="defaultModel">The list of chunks to merge.</param>
+        /// <param name="defaultModel">The default model <see cref="Type"/> name.</param>
         public void MergeInheritedChunkTrees(
             ChunkTree chunkTree,
             IReadOnlyList<ChunkTree> inheritedChunkTrees,
@@ -118,44 +124,34 @@ namespace Microsoft.AspNet.Mvc.Razor.Directives
                 throw new ArgumentNullException(nameof(inheritedChunkTrees));
             }
 
-            var mergerMappings = GetMergerMappings(chunkTree, defaultModel);
+            var chunkMergers = GetChunkMergers(chunkTree, defaultModel);
-            IChunkMerger merger;
-
             // We merge chunks into the ChunkTree in two passes. In the first pass, we traverse the ChunkTree visiting
             // a mapped IChunkMerger for types that are registered.
             foreach (var chunk in chunkTree.Chunks)
             {
-                if (mergerMappings.TryGetValue(chunk.GetType(), out merger))
+                foreach (var merger in chunkMergers)
                 {
                     merger.VisitChunk(chunk);
                 }
             }
 
-            // In the second phase we invoke IChunkMerger.Merge for each chunk that has a mapped merger.
+            var inheritedChunks = _defaultInheritedChunks.Concat(
-            // During this phase, the merger can either add to the ChunkTree or ignore the chunk based on the merging
+                inheritedChunkTrees.SelectMany(tree => tree.Chunks)).ToArray();
-            // rules.
+
-            // Read the chunks outside in - that is chunks from the _ViewImports closest to the page get merged in first
+            foreach (var merger in chunkMergers)
-            // and the furthest one last. This allows the merger to ignore a directive like @model that was previously
-            // seen.
-            var chunksToMerge = inheritedChunkTrees.SelectMany(tree => tree.Chunks)
-                                                  .Concat(_defaultInheritedChunks);
-            foreach (var chunk in chunksToMerge)
             {
-                if (mergerMappings.TryGetValue(chunk.GetType(), out merger))
+                merger.MergeInheritedChunks(chunkTree, inheritedChunks);
-                {
-                    merger.Merge(chunkTree, chunk);
-                }
             }
         }
 
-        private static Dictionary<Type, IChunkMerger> GetMergerMappings(ChunkTree chunkTree, string defaultModel)
+        private static IChunkMerger[] GetChunkMergers(ChunkTree chunkTree, string defaultModel)
         {
             var modelType = ChunkHelper.GetModelTypeName(chunkTree, defaultModel);
-            return new Dictionary<Type, IChunkMerger>
+            return new IChunkMerger[]
             {
-                { typeof(UsingChunk), new UsingChunkMerger() },
+                new UsingChunkMerger(),
-                { typeof(InjectChunk), new InjectChunkMerger(modelType) },
+                new InjectChunkMerger(modelType),
-                { typeof(SetBaseTypeChunk), new SetBaseTypeChunkMerger(modelType) }
+                new SetBaseTypeChunkMerger(modelType)
             };
         }
 

src/Microsoft.AspNet.Mvc.Razor.Host/Directives/IChunkMerger.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 Microsoft.AspNet.Razor.Chunks;
 
 namespace Microsoft.AspNet.Mvc.Razor.Directives
@@ -20,7 +21,7 @@ namespace Microsoft.AspNet.Mvc.Razor.Directives
         /// Merges an inherited <see cref="Chunk"/> into the <see cref="ChunkTree"/>.
         /// </summary>
         /// <param name="ChunkTree">The <see cref="ChunkTree"/> to merge into.</param>
-        /// <param name="chunk">The <see cref="Chunk"/> to merge.</param>
+        /// <param name="inheritedChunks">The <see cref="IReadOnlyList{Chunk}"/>s to merge.</param>
-        void Merge(ChunkTree chunkTree, Chunk chunk);
+        void MergeInheritedChunks(ChunkTree chunkTree, IReadOnlyList<Chunk> inheritedChunks);
     }
 }

src/Microsoft.AspNet.Mvc.Razor.Host/Directives/InjectChunkMerger.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using Microsoft.AspNet.Razor.Chunks;
 
 namespace Microsoft.AspNet.Mvc.Razor.Directives
@@ -37,29 +38,35 @@ namespace Microsoft.AspNet.Mvc.Razor.Directives
                 throw new ArgumentNullException(nameof(chunk));
             }
 
-            var injectChunk = ChunkHelper.EnsureChunk<InjectChunk>(chunk);
+            var injectChunk = chunk as InjectChunk;
-            injectChunk.TypeName = ChunkHelper.ReplaceTModel(injectChunk.TypeName, _modelType);
+            if (injectChunk != null)
-            _addedMemberNames.Add(injectChunk.MemberName);
+            {
+                injectChunk.TypeName = ChunkHelper.ReplaceTModel(injectChunk.TypeName, _modelType);
+                _addedMemberNames.Add(injectChunk.MemberName);
+            }
         }
 
         /// <inheritdoc />
-        public void Merge(ChunkTree chunkTree, Chunk chunk)
+        public void MergeInheritedChunks(ChunkTree chunkTree, IReadOnlyList<Chunk> inheritedChunks)
         {
             if (chunkTree == null)
             {
                 throw new ArgumentNullException(nameof(chunkTree));
             }
 
-            if (chunk == null)
+            if (inheritedChunks == null)
             {
-                throw new ArgumentNullException(nameof(chunk));
+                throw new ArgumentNullException(nameof(inheritedChunks));
             }
 
-            var injectChunk = ChunkHelper.EnsureChunk<InjectChunk>(chunk);
+            for (var i = inheritedChunks.Count - 1; i >= 0; i--)
-            if (!_addedMemberNames.Contains(injectChunk.MemberName))
             {
-                _addedMemberNames.Add(injectChunk.MemberName);
+                var injectChunk = inheritedChunks[i] as InjectChunk;
-                chunkTree.Chunks.Add(TransformChunk(injectChunk));
+                if (injectChunk != null &&
+                    _addedMemberNames.Add(injectChunk.MemberName))
+                {
+                    chunkTree.Chunks.Add(TransformChunk(injectChunk));
+                }
             }
         }
 

src/Microsoft.AspNet.Mvc.Razor.Host/Directives/SetBaseTypeChunkMerger.cs

@@ -2,6 +2,8 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Collections.Generic;
+using System.Linq;
 using Microsoft.AspNet.Razor.Chunks;
 
 namespace Microsoft.AspNet.Mvc.Razor.Directives
@@ -31,32 +33,38 @@ namespace Microsoft.AspNet.Mvc.Razor.Directives
                 throw new ArgumentNullException(nameof(chunk));
             }
 
-            var setBaseTypeChunk = ChunkHelper.EnsureChunk<SetBaseTypeChunk>(chunk);
+            var setBaseTypeChunk = chunk as SetBaseTypeChunk;
-            setBaseTypeChunk.TypeName = ChunkHelper.ReplaceTModel(setBaseTypeChunk.TypeName, _modelType);
+            if (setBaseTypeChunk != null)
-            _isBaseTypeSet = true;
+            {
+                setBaseTypeChunk.TypeName = ChunkHelper.ReplaceTModel(setBaseTypeChunk.TypeName, _modelType);
+                _isBaseTypeSet = true;
+            }
         }
 
         /// <inheritdoc />
-        public void Merge(ChunkTree chunkTree, Chunk chunk)
+        public void MergeInheritedChunks(ChunkTree chunkTree, IReadOnlyList<Chunk> inheritedChunks)
         {
             if (chunkTree == null)
             {
                 throw new ArgumentNullException(nameof(chunkTree));
             }
 
-            if (chunk == null)
+            if (inheritedChunks == null)
             {
-                throw new ArgumentNullException(nameof(chunk));
+                throw new ArgumentNullException(nameof(inheritedChunks));
             }
 
             if (!_isBaseTypeSet)
             {
-                var baseTypeChunk = ChunkHelper.EnsureChunk<SetBaseTypeChunk>(chunk);
+                for (var i = inheritedChunks.Count - 1; i >= 0; i--)
-
+                {
-                // The base type can set exactly once and the first one we encounter wins.
+                    var baseTypeChunk = inheritedChunks[i] as SetBaseTypeChunk;
-                _isBaseTypeSet = true;
+                    if (baseTypeChunk != null)
-
+                    {
-                chunkTree.Chunks.Add(TransformChunk(baseTypeChunk));
+                        chunkTree.Chunks.Add(TransformChunk(baseTypeChunk));
+                        break;
+                    }
+                }
             }
         }
 

src/Microsoft.AspNet.Mvc.Razor.Host/Directives/UsingChunkMerger.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using Microsoft.AspNet.Razor.Chunks;
 
 namespace Microsoft.AspNet.Mvc.Razor.Directives
@@ -22,29 +23,33 @@ namespace Microsoft.AspNet.Mvc.Razor.Directives
                 throw new ArgumentNullException(nameof(chunk));
             }
 
-            var namespaceChunk = ChunkHelper.EnsureChunk<UsingChunk>(chunk);
+            var namespaceChunk = chunk as UsingChunk;
-            _currentUsings.Add(namespaceChunk.Namespace);
+            if (namespaceChunk != null)
+            {
+                _currentUsings.Add(namespaceChunk.Namespace);
+            }
         }
 
         /// <inheritdoc />
-        public void Merge(ChunkTree chunkTree, Chunk chunk)
+        public void MergeInheritedChunks(ChunkTree chunkTree, IReadOnlyList<Chunk> inheritedChunks)
         {
             if (chunkTree == null)
             {
                 throw new ArgumentNullException(nameof(chunkTree));
             }
 
-            if (chunk == null)
+            if (inheritedChunks == null)
             {
-                throw new ArgumentNullException(nameof(chunk));
+                throw new ArgumentNullException(nameof(inheritedChunks));
             }
 
-            var namespaceChunk = ChunkHelper.EnsureChunk<UsingChunk>(chunk);
+            var namespaceChunks = inheritedChunks.OfType<UsingChunk>();
-
+            foreach (var namespaceChunk in namespaceChunks)
-            if (!_currentUsings.Contains(namespaceChunk.Namespace))
             {
-                _currentUsings.Add(namespaceChunk.Namespace);
+                if (_currentUsings.Add(namespaceChunk.Namespace))
-                chunkTree.Chunks.Add(namespaceChunk);
+                {
+                    chunkTree.Chunks.Add(namespaceChunk);
+                }
             }
         }
     }

src/Microsoft.AspNet.Mvc.Razor.Host/MvcRazorParser.cs

@@ -117,15 +117,8 @@ namespace Microsoft.AspNet.Mvc.Razor
         {
             var descriptors = new List<TagHelperDirectiveDescriptor>();
 
-            // For tag helpers, the @removeTagHelper only applies tag helpers that were added prior to it.
+            var inheritedChunks = defaultInheritedChunks.Concat(inheritedChunkTrees.SelectMany(tree => tree.Chunks));
-            // Consequently we must visit tag helpers outside-in - furthest _ViewImports first and nearest one last.
+            foreach (var chunk in inheritedChunks)
-            // This is different from the behavior of chunk merging where we visit the nearest one first and ignore
-            // chunks that were previously visited.
-            var chunksFromViewImports = inheritedChunkTrees
-                .Reverse()
-                .SelectMany(tree => tree.Chunks);
-            var chunksInOrder = defaultInheritedChunks.Concat(chunksFromViewImports);
-            foreach (var chunk in chunksInOrder)
             {
                 // All TagHelperDirectiveDescriptors created here have undefined source locations because the source
                 // that created them is not in the same file.

src/Microsoft.AspNet.Mvc.Razor.Host/Properties/Resources.Designer.cs

@@ -26,22 +26,6 @@ namespace Microsoft.AspNet.Mvc.Razor.Host
             return GetString("ArgumentCannotBeNullOrEmpy");
         }
 
-        /// <summary>
-        /// Argument must be an instance of '{0}'.
-        /// </summary>
-        internal static string ArgumentMustBeOfType
-        {
-            get { return GetString("ArgumentMustBeOfType"); }
-        }
-
-        /// <summary>
-        /// Argument must be an instance of '{0}'.
-        /// </summary>
-        internal static string FormatArgumentMustBeOfType(object p0)
-        {
-            return string.Format(CultureInfo.CurrentCulture, GetString("ArgumentMustBeOfType"), p0);
-        }
-
         /// <summary>
         /// The 'inherits' keyword is not allowed when a '{0}' keyword is used.
         /// </summary>

src/Microsoft.AspNet.Mvc.Razor.Host/Resources.resx

@@ -120,9 +120,6 @@
   <data name="ArgumentCannotBeNullOrEmpy" xml:space="preserve">
     <value>Value cannot be null or empty.</value>
   </data>
-  <data name="ArgumentMustBeOfType" xml:space="preserve">
-    <value>Argument must be an instance of '{0}'.</value>
-  </data>
   <data name="MvcRazorCodeParser_CannotHaveModelAndInheritsKeyword" xml:space="preserve">
     <value>The 'inherits' keyword is not allowed when a '{0}' keyword is used.</value>
   </data>

test/Microsoft.AspNet.Mvc.FunctionalTests/TagHelpersTest.cs

@@ -152,6 +152,19 @@ page:<root>root-content</root>"
             Assert.Equal(expected, result.Trim(), ignoreLineEndingDifferences: true);
         }
 
+        [Fact]
+        public async Task DefaultInheritedTagsCanBeRemoved()
+        {
+            // Arrange
+            var expected =
+@"<a href=""~/VirtualPath"">Virtual path</a>";
+
+            var result = await Client.GetStringAsync("RemoveDefaultInheritedTagHelpers");
+
+            // Assert
+            Assert.Equal(expected, result.Trim(), ignoreLineEndingDifferences: true);
+        }
+
         [Fact]
         public async Task ViewsWithModelMetadataAttributes_CanRenderForm()
         {

test/Microsoft.AspNet.Mvc.Razor.Host.Test/Directives/ChunkInheritanceUtilityTest.cs

@@ -40,28 +40,6 @@ namespace Microsoft.AspNet.Mvc.Razor.Directives
 
             // Assert
             Assert.Collection(chunkTreeResults,
-                chunkTreeResult =>
-                {
-                    var viewImportsPath = PlatformNormalizer.NormalizePath(@"Views\home\_ViewImports.cshtml");
-                    Assert.Collection(chunkTreeResult.ChunkTree.Chunks,
-                        chunk =>
-                        {
-                            Assert.IsType<LiteralChunk>(chunk);
-                            Assert.Equal(viewImportsPath, chunk.Start.FilePath);
-                        },
-                        chunk =>
-                        {
-                            var usingChunk = Assert.IsType<UsingChunk>(chunk);
-                            Assert.Equal("MyNamespace", usingChunk.Namespace);
-                            Assert.Equal(viewImportsPath, chunk.Start.FilePath);
-                        },
-                        chunk =>
-                        {
-                            Assert.IsType<LiteralChunk>(chunk);
-                            Assert.Equal(viewImportsPath, chunk.Start.FilePath);
-                        });
-                    Assert.Equal(viewImportsPath, chunkTreeResult.FilePath);
-                },
                 chunkTreeResult =>
                 {
                     var viewImportsPath = PlatformNormalizer.NormalizePath(@"Views\_ViewImports.cshtml");
@@ -88,7 +66,6 @@ namespace Microsoft.AspNet.Mvc.Razor.Directives
                             var setBaseTypeChunk = Assert.IsType<SetBaseTypeChunk>(chunk);
                             Assert.Equal("MyBaseType", setBaseTypeChunk.TypeName);
                             Assert.Equal(viewImportsPath, chunk.Start.FilePath);
-
                         },
                         chunk =>
                         {
@@ -106,6 +83,28 @@ namespace Microsoft.AspNet.Mvc.Razor.Directives
                             Assert.Equal(viewImportsPath, chunk.Start.FilePath);
                         });
                     Assert.Equal(viewImportsPath, chunkTreeResult.FilePath);
+                },
+                chunkTreeResult =>
+                {
+                    var viewImportsPath = PlatformNormalizer.NormalizePath(@"Views\home\_ViewImports.cshtml");
+                    Assert.Collection(chunkTreeResult.ChunkTree.Chunks,
+                        chunk =>
+                        {
+                            Assert.IsType<LiteralChunk>(chunk);
+                            Assert.Equal(viewImportsPath, chunk.Start.FilePath);
+                        },
+                        chunk =>
+                        {
+                            var usingChunk = Assert.IsType<UsingChunk>(chunk);
+                            Assert.Equal("MyNamespace", usingChunk.Namespace);
+                            Assert.Equal(viewImportsPath, chunk.Start.FilePath);
+                        },
+                        chunk =>
+                        {
+                            Assert.IsType<LiteralChunk>(chunk);
+                            Assert.Equal(viewImportsPath, chunk.Start.FilePath);
+                        });
+                    Assert.Equal(viewImportsPath, chunkTreeResult.FilePath);
                 });
         }
 
@@ -173,10 +172,10 @@ namespace Microsoft.AspNet.Mvc.Razor.Directives
             utility.MergeInheritedChunkTrees(chunkTree, inheritedChunkTrees, "dynamic");
 
             // Assert
-            Assert.Equal(3, chunkTree.Chunks.Count);
+            Assert.Collection(chunkTree.Chunks,
-            Assert.Same(inheritedChunkTrees[0].Chunks[0], chunkTree.Chunks[0]);
+                chunk => Assert.Same(defaultChunks[1], chunk),
-            Assert.Same(inheritedChunkTrees[1].Chunks[0], chunkTree.Chunks[1]);
+                chunk => Assert.Same(inheritedChunkTrees[0].Chunks[0], chunk),
-            Assert.Same(defaultChunks[0], chunkTree.Chunks[2]);
+                chunk => Assert.Same(defaultChunks[0], chunk));
         }
     }
 }

test/Microsoft.AspNet.Mvc.Razor.Host.Test/Directives/InjectChunkMergerTest.cs

@@ -2,24 +2,12 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using Microsoft.AspNet.Razor.Chunks;
-using Microsoft.AspNet.Testing;
 using Xunit;
 
 namespace Microsoft.AspNet.Mvc.Razor.Directives
 {
     public class InjectChunkMergerTest
     {
-        [Fact]
-        public void Visit_ThrowsIfThePassedInChunkIsNotAInjectChunk()
-        {
-            // Arrange
-            var expected = "Argument must be an instance of 'Microsoft.AspNet.Mvc.Razor.InjectChunk'.";
-            var merger = new InjectChunkMerger("dynamic");
-
-            // Act and Assert
-            ExceptionAssert.ThrowsArgument(() => merger.VisitChunk(new LiteralChunk()), "chunk", expected);
-        }
-
         [Theory]
         [InlineData("MyApp.TestHelper<TModel>", "MyApp.TestHelper<Person>")]
         [InlineData("TestBaseType", "TestBaseType")]
@@ -37,17 +25,6 @@ namespace Microsoft.AspNet.Mvc.Razor.Directives
             Assert.Equal("TestHelper", chunk.MemberName);
         }
 
-        [Fact]
-        public void Merge_ThrowsIfThePassedInChunkIsNotAInjectChunk()
-        {
-            // Arrange
-            var expected = "Argument must be an instance of 'Microsoft.AspNet.Mvc.Razor.InjectChunk'.";
-            var merger = new InjectChunkMerger("dynamic");
-
-            // Act and Assert
-            ExceptionAssert.ThrowsArgument(() => merger.Merge(new ChunkTree(), new LiteralChunk()), "chunk", expected);
-        }
-
         [Fact]
         public void Merge_AddsChunkIfChunkWithMatchingPropertyNameWasNotVisitedInChunkTree()
         {
@@ -56,9 +33,13 @@ namespace Microsoft.AspNet.Mvc.Razor.Directives
             var expectedProperty = "MyHelper";
             var merger = new InjectChunkMerger("dynamic");
             var chunkTree = new ChunkTree();
+            var inheritedChunks = new[]
+            {
+                new InjectChunk(expectedType, expectedProperty)
+            };
 
             // Act
-            merger.Merge(chunkTree, new InjectChunk(expectedType, expectedProperty));
+            merger.MergeInheritedChunks(chunkTree, inheritedChunks);
 
             // Assert
             var chunk = Assert.Single(chunkTree.Chunks);
@@ -73,10 +54,14 @@ namespace Microsoft.AspNet.Mvc.Razor.Directives
             // Arrange
             var merger = new InjectChunkMerger("dynamic");
             var chunkTree = new ChunkTree();
+            var inheritedChunks = new[]
+            {
+                new InjectChunk("MyTypeB", "MyProperty")
+            };
 
             // Act
             merger.VisitChunk(new InjectChunk("MyTypeA", "MyProperty"));
-            merger.Merge(chunkTree, new InjectChunk("MyTypeB", "MyProperty"));
+            merger.MergeInheritedChunks(chunkTree, inheritedChunks);
 
             // Assert
             Assert.Empty(chunkTree.Chunks);
@@ -88,11 +73,15 @@ namespace Microsoft.AspNet.Mvc.Razor.Directives
             // Arrange
             var merger = new InjectChunkMerger("dynamic");
             var chunkTree = new ChunkTree();
+            var inheritedChunks = new[]
+            {
+                new InjectChunk("MyTypeB", "different-property"),
+                new InjectChunk("MyType", "myproperty"),
+            };
 
             // Act
             merger.VisitChunk(new InjectChunk("MyType", "MyProperty"));
-            merger.Merge(chunkTree, new InjectChunk("MyType", "myproperty"));
+            merger.MergeInheritedChunks(chunkTree, inheritedChunks);
-            merger.Merge(chunkTree, new InjectChunk("MyTypeB", "different-property"));
 
             // Assert
             Assert.Equal(2, chunkTree.Chunks.Count);
@@ -111,9 +100,13 @@ namespace Microsoft.AspNet.Mvc.Razor.Directives
             // Arrange
             var merger = new InjectChunkMerger("dynamic");
             var chunkTree = new ChunkTree();
+            var inheritedChunks = new[]
+            {
+                new InjectChunk("MyHelper<TModel>", "MyProperty")
+            };
 
             // Act
-            merger.Merge(chunkTree, new InjectChunk("MyHelper<TModel>", "MyProperty"));
+            merger.MergeInheritedChunks(chunkTree, inheritedChunks);
 
             // Assert
             var chunk = Assert.Single(chunkTree.Chunks);
@@ -128,9 +121,13 @@ namespace Microsoft.AspNet.Mvc.Razor.Directives
             // Arrange
             var merger = new InjectChunkMerger("MyTestModel2");
             var chunkTree = new ChunkTree();
+            var inheritedChunks = new[]
+            {
+                new InjectChunk("MyHelper<TModel>", "MyProperty")
+            };
 
             // Act
-            merger.Merge(chunkTree, new InjectChunk("MyHelper<TModel>", "MyProperty"));
+            merger.MergeInheritedChunks(chunkTree, inheritedChunks);
 
             // Assert
             var chunk = Assert.Single(chunkTree.Chunks);
@@ -140,21 +137,36 @@ namespace Microsoft.AspNet.Mvc.Razor.Directives
         }
 
         [Fact]
-        public void Merge_IgnoresChunkIfChunkWithMatchingPropertyNameWasPreviouslyMerged()
+        public void Merge_UsesTheLastInjectChunkOfAPropertyName()
         {
             // Arrange
             var merger = new InjectChunkMerger("dynamic");
             var chunkTree = new ChunkTree();
+            var inheritedChunks = new Chunk[]
+            {
+                new LiteralChunk(),
+                new InjectChunk("SomeOtherType", "Property"),
+                new InjectChunk("DifferentPropertyType", "DifferentProperty"),
+                new InjectChunk("SomeType", "Property"),
+            };
 
             // Act
-            merger.Merge(chunkTree, new InjectChunk("SomeType", "Property"));
+            merger.MergeInheritedChunks(chunkTree, inheritedChunks);
-            merger.Merge(chunkTree, new InjectChunk("SomeOtherType", "Property"));
 
             // Assert
-            var chunk = Assert.Single(chunkTree.Chunks);
+            Assert.Collection(chunkTree.Chunks,
-            var injectChunk = Assert.IsType<InjectChunk>(chunk);
+                chunk =>
-            Assert.Equal("SomeType", injectChunk.TypeName);
+                {
-            Assert.Equal("Property", injectChunk.MemberName);
+                    var injectChunk = Assert.IsType<InjectChunk>(chunk);
+                    Assert.Equal("SomeType", injectChunk.TypeName);
+                    Assert.Equal("Property", injectChunk.MemberName);
+                },
+                chunk =>
+                {
+                    var injectChunk = Assert.IsType<InjectChunk>(chunk);
+                    Assert.Equal("DifferentPropertyType", injectChunk.TypeName);
+                    Assert.Equal("DifferentProperty", injectChunk.MemberName);
+                });
         }
     }
 }

test/Microsoft.AspNet.Mvc.Razor.Host.Test/Directives/SetBaseTypeChunkMergerTest.cs

@@ -2,25 +2,12 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using Microsoft.AspNet.Razor.Chunks;
-using Microsoft.AspNet.Testing;
 using Xunit;
 
 namespace Microsoft.AspNet.Mvc.Razor.Directives
 {
     public class SetBaseTypeChunkMergerTest
     {
-        [Fact]
-        public void Visit_ThrowsIfThePassedInChunkIsNotASetBaseTypeChunk()
-        {
-            // Arrange
-            var expected = "Argument must be an instance of " +
-                           "'Microsoft.AspNet.Razor.Chunks.SetBaseTypeChunk'.";
-            var merger = new SetBaseTypeChunkMerger("dynamic");
-
-            // Act and Assert
-            ExceptionAssert.ThrowsArgument(() => merger.VisitChunk(new LiteralChunk()), "chunk", expected);
-        }
-
         [Theory]
         [InlineData("MyApp.BaseType<TModel>", "MyApp.BaseType<Person>")]
         [InlineData("TestBaseType", "TestBaseType")]
@@ -40,18 +27,6 @@ namespace Microsoft.AspNet.Mvc.Razor.Directives
             Assert.Equal(expectedValue, chunk.TypeName);
         }
 
-        [Fact]
-        public void Merge_ThrowsIfThePassedInChunkIsNotASetBaseTypeChunk()
-        {
-            // Arrange
-            var expected = "Argument must be an instance of " +
-                           "'Microsoft.AspNet.Razor.Chunks.SetBaseTypeChunk'.";
-            var merger = new SetBaseTypeChunkMerger("dynamic");
-
-            // Act and Assert
-            ExceptionAssert.ThrowsArgument(() => merger.Merge(new ChunkTree(), new LiteralChunk()), "chunk", expected);
-        }
-
         [Fact]
         public void Merge_SetsBaseTypeIfItHasNotBeenSetInChunkTree()
         {
@@ -59,9 +34,13 @@ namespace Microsoft.AspNet.Mvc.Razor.Directives
             var expected = "MyApp.Razor.MyBaseType";
             var merger = new SetBaseTypeChunkMerger("dynamic");
             var chunkTree = new ChunkTree();
+            var inheritedChunks = new[]
+            {
+                new SetBaseTypeChunk { TypeName = expected }
+            };
 
             // Act
-            merger.Merge(chunkTree, new SetBaseTypeChunk { TypeName = expected });
+            merger.MergeInheritedChunks(chunkTree, inheritedChunks);
 
             // Assert
             var chunk = Assert.Single(chunkTree.Chunks);
@@ -75,25 +54,34 @@ namespace Microsoft.AspNet.Mvc.Razor.Directives
             // Arrange
             var merger = new SetBaseTypeChunkMerger("dynamic");
             var chunkTree = new ChunkTree();
+            var inheritedChunks = new[]
+            {
+                 new SetBaseTypeChunk { TypeName = "MyBaseType2" }
+            };
 
             // Act
             merger.VisitChunk(new SetBaseTypeChunk { TypeName = "MyBaseType1" });
-            merger.Merge(chunkTree, new SetBaseTypeChunk { TypeName = "MyBaseType2" });
+            merger.MergeInheritedChunks(chunkTree, inheritedChunks);
 
             // Assert
             Assert.Empty(chunkTree.Chunks);
         }
 
         [Fact]
-        public void Merge_IgnoresSetBaseTypeChunksIfSetBaseTypeWasPreviouslyMerged()
+        public void Merge_PicksLastBaseTypeChunkFromChunkTree()
         {
             // Arrange
             var merger = new SetBaseTypeChunkMerger("dynamic");
             var chunkTree = new ChunkTree();
+            var inheritedChunks = new Chunk[]
+            {
+                 new SetBaseTypeChunk { TypeName = "MyBase2" },
+                 new LiteralChunk(),
+                 new SetBaseTypeChunk { TypeName = "MyBase1" },
+            };
 
             // Act
-            merger.Merge(chunkTree, new SetBaseTypeChunk { TypeName = "MyBase1" });
+            merger.MergeInheritedChunks(chunkTree, inheritedChunks);
-            merger.Merge(chunkTree, new SetBaseTypeChunk { TypeName = "MyBase2" });
 
             // Assert
             var chunk = Assert.Single(chunkTree.Chunks);

test/Microsoft.AspNet.Mvc.Razor.Host.Test/Directives/UsingChunkMergerTest.cs

@@ -9,28 +9,6 @@ namespace Microsoft.AspNet.Mvc.Razor.Directives
 {
     public class UsingChunkMergerTest
     {
-        [Fact]
-        public void Visit_ThrowsIfThePassedInChunkIsNotAUsingChunk()
-        {
-            // Arrange
-            var expected = "Argument must be an instance of 'Microsoft.AspNet.Razor.Chunks.UsingChunk'.";
-            var merger = new UsingChunkMerger();
-
-            // Act and Assert
-            ExceptionAssert.ThrowsArgument(() => merger.VisitChunk(new LiteralChunk()), "chunk", expected);
-        }
-
-        [Fact]
-        public void Merge_ThrowsIfThePassedInChunkIsNotAUsingChunk()
-        {
-            // Arrange
-            var expected = "Argument must be an instance of 'Microsoft.AspNet.Razor.Chunks.UsingChunk'.";
-            var merger = new UsingChunkMerger();
-
-            // Act and Assert
-            ExceptionAssert.ThrowsArgument(() => merger.Merge(new ChunkTree(), new LiteralChunk()), "chunk", expected);
-        }
-
         [Fact]
         public void Merge_AddsNamespacesThatHaveNotBeenVisitedInChunkTree()
         {
@@ -38,10 +16,14 @@ namespace Microsoft.AspNet.Mvc.Razor.Directives
             var expected = "MyApp.Models";
             var merger = new UsingChunkMerger();
             var chunkTree = new ChunkTree();
+            var inheritedChunks = new Chunk[]
+            {
+                new UsingChunk { Namespace = expected },
+            };
 
             // Act
             merger.VisitChunk(new UsingChunk { Namespace = "Microsoft.AspNet.Mvc" });
-            merger.Merge(chunkTree, new UsingChunk { Namespace = expected });
+            merger.MergeInheritedChunks(chunkTree, inheritedChunks);
 
             // Assert
             var chunk = Assert.Single(chunkTree.Chunks);
@@ -55,26 +37,36 @@ namespace Microsoft.AspNet.Mvc.Razor.Directives
             // Arrange
             var merger = new UsingChunkMerger();
             var chunkTree = new ChunkTree();
+            var inheritedChunks = new Chunk[]
+            {
+                new UsingChunk { Namespace = "Microsoft.AspNet.Mvc" },
+                new InjectChunk("Foo", "Bar")
+            };
 
             // Act
             merger.VisitChunk(new UsingChunk { Namespace = "Microsoft.AspNet.Mvc" });
-            merger.Merge(chunkTree, new UsingChunk { Namespace = "Microsoft.AspNet.Mvc" });
+            merger.MergeInheritedChunks(chunkTree, inheritedChunks);
 
             // Assert
             Assert.Empty(chunkTree.Chunks);
         }
 
         [Fact]
-        public void Merge_IgnoresNamespacesThatHaveBeenVisitedDuringMerge()
+        public void Merge_DoesNotAddMoreThanOneInstanceOfTheSameInheritedNamespace()
         {
             // Arrange
             var merger = new UsingChunkMerger();
             var chunkTree = new ChunkTree();
+            var inheritedChunks = new Chunk[]
+            {
+                new LiteralChunk(),
+                new UsingChunk { Namespace = "Microsoft.AspNet.Mvc" },
+                new UsingChunk { Namespace = "Microsoft.AspNet.Mvc" },
+                new UsingChunk { Namespace = "Microsoft.AspNet.Mvc.Razor" }
+            };
 
             // Act
-            merger.Merge(chunkTree, new UsingChunk { Namespace = "Microsoft.AspNet.Mvc" });
+            merger.MergeInheritedChunks(chunkTree, inheritedChunks);
-            merger.Merge(chunkTree, new UsingChunk { Namespace = "Microsoft.AspNet.Mvc" });
-            merger.Merge(chunkTree, new UsingChunk { Namespace = "Microsoft.AspNet.Mvc.Razor" });
 
             // Assert
             Assert.Equal(2, chunkTree.Chunks.Count);
@@ -85,15 +77,19 @@ namespace Microsoft.AspNet.Mvc.Razor.Directives
         }
 
         [Fact]
-        public void Merge_MacthesNamespacesInCaseSensitiveManner()
+        public void Merge_MatchesNamespacesInCaseSensitiveManner()
         {
             // Arrange
             var merger = new UsingChunkMerger();
             var chunkTree = new ChunkTree();
+            var inheritedChunks = new[]
+            {
+                new UsingChunk { Namespace = "Microsoft.AspNet.Mvc" },
+                new UsingChunk { Namespace = "Microsoft.AspNet.mvc" }
+            };
 
             // Act
-            merger.Merge(chunkTree, new UsingChunk { Namespace = "Microsoft.AspNet.Mvc" });
+            merger.MergeInheritedChunks(chunkTree, inheritedChunks);
-            merger.Merge(chunkTree, new UsingChunk { Namespace = "Microsoft.AspNet.mvc" });
 
             // Assert
             Assert.Equal(2, chunkTree.Chunks.Count);

test/Microsoft.AspNet.Mvc.Razor.Host.Test/MvcRazorParserTest.cs

@@ -5,7 +5,6 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 using Microsoft.AspNet.Mvc.Rendering;
-using Microsoft.AspNet.Mvc.ViewFeatures;
 using Microsoft.AspNet.Razor;
 using Microsoft.AspNet.Razor.Chunks;
 using Microsoft.AspNet.Razor.Parser;
@@ -66,8 +65,8 @@ namespace Microsoft.AspNet.Mvc.Razor
                     {
                         new[]
                         {
-                            CreateChunkTree(new TagHelperPrefixDirectiveChunk { Prefix = "THP1" }),
                             CreateChunkTree(new TagHelperPrefixDirectiveChunk { Prefix = "THP2" }),
+                            CreateChunkTree(new TagHelperPrefixDirectiveChunk { Prefix = "THP1" }),
                         },
                         new[] { CreateDirectiveDescriptor("THP1", TagHelperDirectiveType.TagHelperPrefix) }
                     },
@@ -89,10 +88,10 @@ namespace Microsoft.AspNet.Mvc.Razor
                     {
                         new[]
                         {
+                            CreateChunkTree(new RemoveTagHelperChunk { LookupText = "RTH" }),
                             CreateChunkTree(
                                 new LiteralChunk { Text = "Hello world" },
                                 new AddTagHelperChunk { LookupText = "ATH" }),
-                            CreateChunkTree(new RemoveTagHelperChunk { LookupText = "RTH" })
                         },
                         new[]
                         {
@@ -103,11 +102,11 @@ namespace Microsoft.AspNet.Mvc.Razor
                     {
                         new[]
                         {
-                            CreateChunkTree(new TagHelperPrefixDirectiveChunk { Prefix = "THP" }),
+                            CreateChunkTree(new RemoveTagHelperChunk { LookupText = "RTH" }),
                             CreateChunkTree(
                                 new LiteralChunk { Text = "Hello world" },
                                 new AddTagHelperChunk { LookupText = "ATH" }),
-                            CreateChunkTree(new RemoveTagHelperChunk { LookupText = "RTH" })
+                            CreateChunkTree(new TagHelperPrefixDirectiveChunk { Prefix = "THP" }),
                         },
                         new[]
                         {
@@ -119,10 +118,10 @@ namespace Microsoft.AspNet.Mvc.Razor
                     {
                         new[]
                         {
-                            CreateChunkTree(new TagHelperPrefixDirectiveChunk { Prefix = "THP1" }),
-                            CreateChunkTree(new AddTagHelperChunk { LookupText = "ATH" }),
-                            CreateChunkTree(new RemoveTagHelperChunk { LookupText = "RTH" }),
                             CreateChunkTree(new TagHelperPrefixDirectiveChunk { Prefix = "THP2" }),
+                            CreateChunkTree(new RemoveTagHelperChunk { LookupText = "RTH" }),
+                            CreateChunkTree(new AddTagHelperChunk { LookupText = "ATH" }),
+                            CreateChunkTree(new TagHelperPrefixDirectiveChunk { Prefix = "THP1" }),
                         },
                         new[]
                         {

test/Microsoft.AspNet.Mvc.Razor.Host.Test/TestFiles/Output/DesignTime/Basic.cs

@@ -16,13 +16,13 @@ namespace Asp
         }
         #line hidden
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.Rendering.IHtmlHelper<dynamic> Html { get; private set; }
+        public Microsoft.AspNet.Mvc.IUrlHelper Url { get; private set; }
-        [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.Rendering.IJsonHelper Json { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
         public Microsoft.AspNet.Mvc.IViewComponentHelper Component { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.IUrlHelper Url { get; private set; }
+        public Microsoft.AspNet.Mvc.Rendering.IJsonHelper Json { get; private set; }
+        [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
+        public Microsoft.AspNet.Mvc.Rendering.IHtmlHelper<dynamic> Html { get; private set; }
 
         #line hidden
 

test/Microsoft.AspNet.Mvc.Razor.Host.Test/TestFiles/Output/DesignTime/Inject.cs

@@ -30,13 +30,13 @@ using MyNamespace
 #line hidden
         { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.Rendering.IHtmlHelper<dynamic> Html { get; private set; }
+        public Microsoft.AspNet.Mvc.IUrlHelper Url { get; private set; }
-        [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.Rendering.IJsonHelper Json { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
         public Microsoft.AspNet.Mvc.IViewComponentHelper Component { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.IUrlHelper Url { get; private set; }
+        public Microsoft.AspNet.Mvc.Rendering.IJsonHelper Json { get; private set; }
+        [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
+        public Microsoft.AspNet.Mvc.Rendering.IHtmlHelper<dynamic> Html { get; private set; }
 
         #line hidden
 

test/Microsoft.AspNet.Mvc.Razor.Host.Test/TestFiles/Output/DesignTime/InjectWithModel.cs

@@ -38,11 +38,11 @@ namespace Asp
 #line hidden
         { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.Rendering.IJsonHelper Json { get; private set; }
+        public Microsoft.AspNet.Mvc.IUrlHelper Url { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
         public Microsoft.AspNet.Mvc.IViewComponentHelper Component { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.IUrlHelper Url { get; private set; }
+        public Microsoft.AspNet.Mvc.Rendering.IJsonHelper Json { get; private set; }
 
         #line hidden
 

test/Microsoft.AspNet.Mvc.Razor.Host.Test/TestFiles/Output/DesignTime/InjectWithSemicolon.cs

@@ -54,11 +54,11 @@ namespace Asp
 #line hidden
         { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.Rendering.IJsonHelper Json { get; private set; }
+        public Microsoft.AspNet.Mvc.IUrlHelper Url { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
         public Microsoft.AspNet.Mvc.IViewComponentHelper Component { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.IUrlHelper Url { get; private set; }
+        public Microsoft.AspNet.Mvc.Rendering.IJsonHelper Json { get; private set; }
 
         #line hidden
 

test/Microsoft.AspNet.Mvc.Razor.Host.Test/TestFiles/Output/DesignTime/Model.cs

@@ -22,13 +22,13 @@ namespace Asp
         }
         #line hidden
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.Rendering.IHtmlHelper<System.Collections.IEnumerable> Html { get; private set; }
+        public Microsoft.AspNet.Mvc.IUrlHelper Url { get; private set; }
-        [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.Rendering.IJsonHelper Json { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
         public Microsoft.AspNet.Mvc.IViewComponentHelper Component { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.IUrlHelper Url { get; private set; }
+        public Microsoft.AspNet.Mvc.Rendering.IJsonHelper Json { get; private set; }
+        [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
+        public Microsoft.AspNet.Mvc.Rendering.IHtmlHelper<System.Collections.IEnumerable> Html { get; private set; }
 
         #line hidden
 

test/Microsoft.AspNet.Mvc.Razor.Host.Test/TestFiles/Output/DesignTime/ModelExpressionTagHelper.cs

@@ -38,13 +38,13 @@ namespace Asp
         }
         #line hidden
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.Rendering.IHtmlHelper<DateTime> Html { get; private set; }
+        public Microsoft.AspNet.Mvc.IUrlHelper Url { get; private set; }
-        [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.Rendering.IJsonHelper Json { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
         public Microsoft.AspNet.Mvc.IViewComponentHelper Component { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.IUrlHelper Url { get; private set; }
+        public Microsoft.AspNet.Mvc.Rendering.IJsonHelper Json { get; private set; }
+        [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
+        public Microsoft.AspNet.Mvc.Rendering.IHtmlHelper<DateTime> Html { get; private set; }
 
         #line hidden
 

test/Microsoft.AspNet.Mvc.Razor.Host.Test/TestFiles/Output/Runtime/Basic.cs

@@ -16,13 +16,13 @@ namespace Asp
         }
         #line hidden
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.Rendering.IHtmlHelper<dynamic> Html { get; private set; }
+        public Microsoft.AspNet.Mvc.IUrlHelper Url { get; private set; }
-        [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.Rendering.IJsonHelper Json { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
         public Microsoft.AspNet.Mvc.IViewComponentHelper Component { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.IUrlHelper Url { get; private set; }
+        public Microsoft.AspNet.Mvc.Rendering.IJsonHelper Json { get; private set; }
+        [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
+        public Microsoft.AspNet.Mvc.Rendering.IHtmlHelper<dynamic> Html { get; private set; }
 
         #line hidden
 

test/Microsoft.AspNet.Mvc.Razor.Host.Test/TestFiles/Output/Runtime/Inject.cs

@@ -24,13 +24,13 @@ using MyNamespace
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
         public MyApp MyPropertyName { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.Rendering.IHtmlHelper<dynamic> Html { get; private set; }
+        public Microsoft.AspNet.Mvc.IUrlHelper Url { get; private set; }
-        [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.Rendering.IJsonHelper Json { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
         public Microsoft.AspNet.Mvc.IViewComponentHelper Component { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.IUrlHelper Url { get; private set; }
+        public Microsoft.AspNet.Mvc.Rendering.IJsonHelper Json { get; private set; }
+        [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
+        public Microsoft.AspNet.Mvc.Rendering.IHtmlHelper<dynamic> Html { get; private set; }
 
         #line hidden
 

test/Microsoft.AspNet.Mvc.Razor.Host.Test/TestFiles/Output/Runtime/InjectWithModel.cs

@@ -26,11 +26,11 @@ namespace Asp
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
         public MyService<MyModel> Html { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.Rendering.IJsonHelper Json { get; private set; }
+        public Microsoft.AspNet.Mvc.IUrlHelper Url { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
         public Microsoft.AspNet.Mvc.IViewComponentHelper Component { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.IUrlHelper Url { get; private set; }
+        public Microsoft.AspNet.Mvc.Rendering.IJsonHelper Json { get; private set; }
 
         #line hidden
 

test/Microsoft.AspNet.Mvc.Razor.Host.Test/TestFiles/Output/Runtime/InjectWithSemicolon.cs

@@ -30,11 +30,11 @@ namespace Asp
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
         public MyService<MyModel> Html2 { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.Rendering.IJsonHelper Json { get; private set; }
+        public Microsoft.AspNet.Mvc.IUrlHelper Url { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
         public Microsoft.AspNet.Mvc.IViewComponentHelper Component { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.IUrlHelper Url { get; private set; }
+        public Microsoft.AspNet.Mvc.Rendering.IJsonHelper Json { get; private set; }
 
         #line hidden
 

test/Microsoft.AspNet.Mvc.Razor.Host.Test/TestFiles/Output/Runtime/Model.cs

@@ -22,13 +22,13 @@ namespace Asp
         }
         #line hidden
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.Rendering.IHtmlHelper<System.Collections.IEnumerable> Html { get; private set; }
+        public Microsoft.AspNet.Mvc.IUrlHelper Url { get; private set; }
-        [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.Rendering.IJsonHelper Json { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
         public Microsoft.AspNet.Mvc.IViewComponentHelper Component { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.IUrlHelper Url { get; private set; }
+        public Microsoft.AspNet.Mvc.Rendering.IJsonHelper Json { get; private set; }
+        [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
+        public Microsoft.AspNet.Mvc.Rendering.IHtmlHelper<System.Collections.IEnumerable> Html { get; private set; }
 
         #line hidden
 

test/Microsoft.AspNet.Mvc.Razor.Host.Test/TestFiles/Output/Runtime/ModelExpressionTagHelper.cs

@@ -31,13 +31,13 @@ namespace Asp
         }
         #line hidden
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.Rendering.IHtmlHelper<DateTime> Html { get; private set; }
+        public Microsoft.AspNet.Mvc.IUrlHelper Url { get; private set; }
-        [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.Rendering.IJsonHelper Json { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
         public Microsoft.AspNet.Mvc.IViewComponentHelper Component { get; private set; }
         [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
-        public Microsoft.AspNet.Mvc.IUrlHelper Url { get; private set; }
+        public Microsoft.AspNet.Mvc.Rendering.IJsonHelper Json { get; private set; }
+        [Microsoft.AspNet.Mvc.Razor.Internal.RazorInjectAttribute]
+        public Microsoft.AspNet.Mvc.Rendering.IHtmlHelper<DateTime> Html { get; private set; }
 
         #line hidden
 

test/WebSites/TagHelpersWebSite/Controllers/RemoveDefaultInheritedTagHelpersController.cs

@@ -0,0 +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 Microsoft.AspNet.Mvc;
+
+namespace TagHelpersWebSite.Controllers
+{
+    public class RemoveDefaultInheritedTagHelpersController : Controller
+    {
+        public IActionResult Index() => View();
+    }
+}

test/WebSites/TagHelpersWebSite/Views/RemoveDefaultInheritedTagHelpers/Index.cshtml

@@ -0,0 +1,4 @@
+@{ 
+    Layout = null;
+}
+<a href="~/VirtualPath">Virtual path</a>

test/WebSites/TagHelpersWebSite/Views/RemoveDefaultInheritedTagHelpers/_ViewImports.cshtml

@@ -0,0 +1 @@
+@removeTagHelper "*, Microsoft.AspNet.Mvc.Razor"