Changes to make EnableInstrumentation conditionally enabled

Mvc.sln

@@ -1,7 +1,7 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio 14
-VisualStudioVersion = 14.0.22013.1
+VisualStudioVersion = 14.0.22130.0
 MinimumVisualStudioVersion = 10.0.40219.1
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "samples", "samples", "{DAAE4C74-D06F-4874-A166-33305D2643CE}"
 EndProject
@@ -86,6 +86,8 @@ Project("{8BB2217D-0F2D-49D1-97BC-3654ED321F3B}") = "ReflectedModelWebSite", "te
 EndProject
 Project("{8BB2217D-0F2D-49D1-97BC-3654ED321F3B}") = "FilesWebSite", "test\WebSites\FilesWebSite\FilesWebSite.kproj", "{0EF9860B-10D7-452F-B0F4-A405B88BEBB3}"
 EndProject
+Project("{8BB2217D-0F2D-49D1-97BC-3654ED321F3B}") = "RazorInstrumentationWebSite", "test\WebSites\RazorInstrumentationWebSite\RazorInstrumentationWebSite.kproj", "{2B2B9876-903C-4065-8D62-2EE832BBA106}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -446,6 +448,16 @@ Global
 		{C2EF54F8-8886-4260-A322-44F76245F95D}.Release|Mixed Platforms.ActiveCfg = Release|Any CPU
 		{C2EF54F8-8886-4260-A322-44F76245F95D}.Release|Mixed Platforms.Build.0 = Release|Any CPU
 		{C2EF54F8-8886-4260-A322-44F76245F95D}.Release|x86.ActiveCfg = Release|Any CPU
+		{2B2B9876-903C-4065-8D62-2EE832BBA106}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{2B2B9876-903C-4065-8D62-2EE832BBA106}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{2B2B9876-903C-4065-8D62-2EE832BBA106}.Debug|Mixed Platforms.ActiveCfg = Debug|Any CPU
+		{2B2B9876-903C-4065-8D62-2EE832BBA106}.Debug|Mixed Platforms.Build.0 = Debug|Any CPU
+		{2B2B9876-903C-4065-8D62-2EE832BBA106}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{2B2B9876-903C-4065-8D62-2EE832BBA106}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{2B2B9876-903C-4065-8D62-2EE832BBA106}.Release|Any CPU.Build.0 = Release|Any CPU
+		{2B2B9876-903C-4065-8D62-2EE832BBA106}.Release|Mixed Platforms.ActiveCfg = Release|Any CPU
+		{2B2B9876-903C-4065-8D62-2EE832BBA106}.Release|Mixed Platforms.Build.0 = Release|Any CPU
+		{2B2B9876-903C-4065-8D62-2EE832BBA106}.Release|x86.ActiveCfg = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -487,5 +499,6 @@ Global
 		{0EF9860B-10D7-452F-B0F4-A405B88BEBB3} = {16703B76-C9F7-4C75-AE6C-53D92E308E3C}
 		{61061528-071E-424E-965A-07BCC2F02672} = {16703B76-C9F7-4C75-AE6C-53D92E308E3C}
 		{C2EF54F8-8886-4260-A322-44F76245F95D} = {16703B76-C9F7-4C75-AE6C-53D92E308E3C}
+		{2B2B9876-903C-4065-8D62-2EE832BBA106} = {16703B76-C9F7-4C75-AE6C-53D92E308E3C}
 	EndGlobalSection
 EndGlobal

src/Microsoft.AspNet.Mvc.Razor/Compilation/CompilerCache.cs

@@ -64,25 +64,30 @@ namespace Microsoft.AspNet.Mvc.Razor
             return false;
         }
 
-        public CompilationResult GetOrAdd(RelativeFileInfo fileInfo, Func<CompilationResult> compile)
+        public CompilationResult GetOrAdd([NotNull] RelativeFileInfo fileInfo,
+                                          bool enableInstrumentation,
+                                          [NotNull] Func<CompilationResult> compile)
         {
             CompilerCacheEntry cacheEntry;
             if (!_cache.TryGetValue(fileInfo.RelativePath, out cacheEntry))
             {
-                return OnCacheMiss(fileInfo, compile);
+                return OnCacheMiss(fileInfo, enableInstrumentation, compile);
             }
             else
             {
-                if (cacheEntry.Length != fileInfo.FileInfo.Length)
+                if ((cacheEntry.Length != fileInfo.FileInfo.Length) ||
+                    (enableInstrumentation && !cacheEntry.IsInstrumented))
                 {
-                    // it's not a match, recompile
-                    return OnCacheMiss(fileInfo, compile);
+                    // Recompile if
+                    // (a) If the file lengths differ
+                    // (b) If the compiled type is not instrumented but we require it to be instrumented.
+                    return OnCacheMiss(fileInfo, enableInstrumentation, compile);
                 }
 
                 if (cacheEntry.LastModified == fileInfo.FileInfo.LastModified)
                 {
                     // Match, not update needed
-                    return CompilationResult.Successful(cacheEntry.ViewType);
+                    return CompilationResult.Successful(cacheEntry.CompiledType);
                 }
 
                 var hash = RazorFileHash.GetHash(fileInfo.FileInfo);
@@ -92,20 +97,24 @@ namespace Microsoft.AspNet.Mvc.Razor
                     string.Equals(cacheEntry.Hash, hash, StringComparison.Ordinal))
                 {
                     // Cache hit, but we need to update the entry
-                    return OnCacheMiss(fileInfo, () => CompilationResult.Successful(cacheEntry.ViewType));
+                    return OnCacheMiss(fileInfo,
+                                       enableInstrumentation,
+                                       () => CompilationResult.Successful(cacheEntry.CompiledType));
                 }
 
                 // it's not a match, recompile
-                return OnCacheMiss(fileInfo, compile);
+                return OnCacheMiss(fileInfo, enableInstrumentation, compile);
             }
         }
 
-        private CompilationResult OnCacheMiss(RelativeFileInfo file, Func<CompilationResult> compile)
+        private CompilationResult OnCacheMiss(RelativeFileInfo file,
+                                              bool isInstrumented,
+                                              Func<CompilationResult> compile)
         {
             var result = compile();
 
-            var cacheEntry = new CompilerCacheEntry(file, result.CompiledType);
-            _cache.AddOrUpdate(file.RelativePath, cacheEntry, (a, b) => cacheEntry);
+            var cacheEntry = new CompilerCacheEntry(file, result.CompiledType, isInstrumented);
+            _cache[file.RelativePath] = cacheEntry;
 
             return result;
         }

src/Microsoft.AspNet.Mvc.Razor/Compilation/CompilerCacheEntry.cs

@@ -5,35 +5,74 @@ using System;
 
 namespace Microsoft.AspNet.Mvc.Razor
 {
+    /// <summary>
+    /// An entry in <see cref="CompilerCache"/> that contain metadata about precompiled and dynamically compiled file.
+    /// </summary>
     public class CompilerCacheEntry
     {
-        public CompilerCacheEntry([NotNull] RazorFileInfo info, [NotNull] Type viewType)
+        /// <summary>
+        /// Initializes a new instance of <see cref="CompilerCacheEntry"/> for a file that was precompiled.
+        /// </summary>
+        /// <param name="info">Metadata about the precompiled file.</param>
+        /// <param name="compiledType">The compiled <see cref="Type"/>.</param>
+        public CompilerCacheEntry([NotNull] RazorFileInfo info, [NotNull] Type compiledType)
         {
-            ViewType = viewType;
+            CompiledType = compiledType;
             RelativePath = info.RelativePath;
             Length = info.Length;
             LastModified = info.LastModified;
             Hash = info.Hash;
         }
 
-        public CompilerCacheEntry([NotNull] RelativeFileInfo info, [NotNull] Type viewType)
+        /// <summary>
+        /// Initializes a new instance of <see cref="CompilerCacheEntry"/> for a file that was dynamically compiled.
+        /// </summary>
+        /// <param name="info">Metadata about the file that was compiled.</param>
+        /// <param name="compiledType">The compiled <see cref="Type"/>.</param>
+        /// <param name="isInstrumented">Flag that indicates that the file was generated with instrumentation
+        /// enabled.</param>
+        public CompilerCacheEntry([NotNull] RelativeFileInfo info, [NotNull] Type compiledType, bool isInstrumented)
         {
-            ViewType = viewType;
+            CompiledType = compiledType;
             RelativePath = info.RelativePath;
             Length = info.FileInfo.Length;
             LastModified = info.FileInfo.LastModified;
+            IsInstrumented = isInstrumented;
         }
 
-        public Type ViewType { get; set; }
-        public string RelativePath { get; set; }
-        public long Length { get; set; }
-        public DateTime LastModified { get; set; }
+        /// <summary>
+        /// Gets the <see cref="Type"/> produced as a result of compilation.
+        /// </summary>
+        public Type CompiledType { get; private set; }
 
         /// <summary>
-        /// The file hash, should only be available for pre compiled files.
+        /// Gets the path of the compiled file relative to the root of the application.
         /// </summary>
-        public string Hash { get; set; }
+        public string RelativePath { get; private set; }
 
+        /// <summary>
+        /// Gets the size of file (in bytes) on disk.
+        /// </summary>
+        public long Length { get; private set; }
+
+        /// <summary>
+        /// Gets the last modified <see cref="DateTime"/> for the file that was compiled at the time of compilation.
+        /// </summary>
+        public DateTime LastModified { get; private set; }
+
+        /// <summary>
+        /// Gets the file hash, should only be available for pre compiled files.
+        /// </summary>
+        public string Hash { get; private set; }
+
+        /// <summary>
+        /// Gets a flag that indicates if the file is precompiled.
+        /// </summary>
         public bool IsPreCompiled {  get { return Hash != null; } }
+
+        /// <summary>
+        /// Gets a flag that indiciates if the page execution in <see cref="CompiledType"/> is instrumeted.
+        /// </summary>
+        public bool IsInstrumented { get; private set; }
     }
 }

src/Microsoft.AspNet.Mvc.Razor/IRazorPageFactory.cs

@@ -12,7 +12,8 @@ namespace Microsoft.AspNet.Mvc.Razor
         /// Creates a <see cref="IRazorPage"/> for the specified path.
         /// </summary>
         /// <param name="relativePath">The path to locate the page.</param>
+        /// <param name="enableInstrumentation">Indicates that execution of the page should be instrumented.</param>
         /// <returns>The IRazorPage instance if it exists, null otherwise.</returns>
-        IRazorPage CreateInstance(string relativePath);
+        IRazorPage CreateInstance(string relativePath, bool enableInstrumentation);
     }
 }

src/Microsoft.AspNet.Mvc.Razor/IRazorView.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using Microsoft.AspNet.Mvc.Rendering;
+using Microsoft.AspNet.PageExecutionInstrumentation;
 
 namespace Microsoft.AspNet.Mvc.Razor
 {
@@ -17,6 +18,8 @@ namespace Microsoft.AspNet.Mvc.Razor
         /// </summary>
         /// <param name="razorPage">The <see cref="IRazorPage"/> instance to execute.</param>
         /// <param name="isPartial">Determines if the view is to be executed as a partial.</param>
-        void Contextualize(IRazorPage razorPage, bool isPartial);
+        void Contextualize(IRazorPage razorPage,
+                           bool isPartial,
+                           IPageExecutionListenerFeature pageExecutionListenerFeature);
     }
 }

src/Microsoft.AspNet.Mvc.Razor/IViewStartProvider.cs

@@ -15,7 +15,8 @@ namespace Microsoft.AspNet.Mvc.Razor
         /// that are applicable to the specified view.
         /// </summary>
         /// <param name="path">The path of the page to locate ViewStart files for.</param>
+        /// <param name="enableInstrumentation">Indicates that execution of the page should be instrumented.</param>
         /// <returns>A sequence of <see cref="IRazorPage"/> that represent ViewStart.</returns>
-        IEnumerable<IRazorPage> GetViewStartPages(string path);
+        IEnumerable<IRazorPage> GetViewStartPages(string path, bool enableInstrumentation);
     }
 }

src/Microsoft.AspNet.Mvc.Razor/Razor/IRazorCompilationService.cs

@@ -3,8 +3,19 @@
 
 namespace Microsoft.AspNet.Mvc.Razor
 {
+    /// <summary>
+    /// Specifies the contracts for a service that compiles Razor files.
+    /// </summary>
     public interface IRazorCompilationService
     {
-        CompilationResult Compile(RelativeFileInfo fileInfo);
+        /// <summary>
+        /// Compiles the razor file located at <paramref name="fileInfo"/>.
+        /// </summary>
+        /// <param name="fileInfo">A <see cref="RelativeFileInfo"/> instance that represents the file to compile.
+        /// </param>
+        /// <param name="isInstrumented">Indicates that the page should be instrumented.</param>
+        /// <returns>A <see cref="CompilationResult"/> that represents the results of parsing and compiling the file.
+        /// </returns>
+        CompilationResult Compile(RelativeFileInfo fileInfo, bool isInstrumented);
     }
 }

src/Microsoft.AspNet.Mvc.Razor/Razor/RazorCompilationService.cs

@@ -6,9 +6,14 @@ using Microsoft.AspNet.Razor;
 
 namespace Microsoft.AspNet.Mvc.Razor
 {
+    /// <summary>
+    /// Default implementation of <see cref="IRazorCompilationService"/>.
+    /// </summary>
+    /// <remarks>
+    /// This class must be registered as a singleton service for the caching to work.
+    /// </remarks>
     public class RazorCompilationService : IRazorCompilationService
     {
-        // This class must be registered as a singleton service for the caching to work.
         private readonly CompilerCache _cache;
         private readonly ICompilationService _baseCompilationService;
         private readonly IMvcRazorHost _razorHost;
@@ -22,13 +27,16 @@ namespace Microsoft.AspNet.Mvc.Razor
             _cache = new CompilerCache(_controllerAssemblyProvider.CandidateAssemblies);
         }
 
-        public CompilationResult Compile([NotNull] RelativeFileInfo file)
+        /// <inheritdoc />
+        public CompilationResult Compile([NotNull] RelativeFileInfo file, bool isInstrumented)
         {
-            return _cache.GetOrAdd(file, () => CompileCore(file));
+            return _cache.GetOrAdd(file, isInstrumented, () => CompileCore(file, isInstrumented));
         }
 
-        internal CompilationResult CompileCore(RelativeFileInfo file)
+        internal CompilationResult CompileCore(RelativeFileInfo file, bool isInstrumented)
         {
+            _razorHost.EnableInstrumentation = isInstrumented;
+
             GeneratorResults results;
             using (var inputStream = file.FileInfo.CreateReadStream())
             {

src/Microsoft.AspNet.Mvc.Razor/RazorView.cs

@@ -2,7 +2,9 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.IO;
 using System.Threading.Tasks;
+using Microsoft.AspNet.PageExecutionInstrumentation;
 
 namespace Microsoft.AspNet.Mvc.Razor
 {
@@ -15,6 +17,7 @@ namespace Microsoft.AspNet.Mvc.Razor
         private readonly IRazorPageFactory _pageFactory;
         private readonly IRazorPageActivator _pageActivator;
         private readonly IViewStartProvider _viewStartProvider;
+        private IPageExecutionListenerFeature _pageExecutionFeature;
         private IRazorPage _razorPage;
         private bool _isPartial;
 
@@ -34,11 +37,19 @@ namespace Microsoft.AspNet.Mvc.Razor
             _viewStartProvider = viewStartProvider;
         }
 
+        private bool EnableInstrumentation
+        {
+            get { return _pageExecutionFeature != null; }
+        }
+
         /// <inheritdoc />
-        public virtual void Contextualize(IRazorPage razorPage, bool isPartial)
+        public virtual void Contextualize([NotNull] IRazorPage razorPage,
+                                          bool isPartial,
+                                          IPageExecutionListenerFeature pageExecutionListener)
         {
             _razorPage = razorPage;
             _isPartial = isPartial;
+            _pageExecutionFeature = pageExecutionListener;
         }
 
         /// <inheritdoc />
@@ -61,45 +72,66 @@ namespace Microsoft.AspNet.Mvc.Razor
             }
         }
 
-        private async Task<RazorTextWriter> RenderPageAsync(IRazorPage page,
-                                                            ViewContext context,
-                                                            bool executeViewStart)
+        private async Task<IBufferedTextWriter> RenderPageAsync(IRazorPage page,
+                                                                ViewContext context,
+                                                                bool executeViewStart)
         {
-            using (var bufferedWriter = new RazorTextWriter(context.Writer, context.Writer.Encoding))
+            var razorTextWriter = new RazorTextWriter(context.Writer, context.Writer.Encoding);
+            TextWriter writer = razorTextWriter;
+            IBufferedTextWriter bufferedWriter = razorTextWriter;
+
+            if (EnableInstrumentation)
             {
-                // The writer for the body is passed through the ViewContext, allowing things like HtmlHelpers
-                // and ViewComponents to reference it.
-                var oldWriter = context.Writer;
-                context.Writer = bufferedWriter;
-
-                try
+                writer = _pageExecutionFeature.DecorateWriter(razorTextWriter);
+                bufferedWriter = writer as IBufferedTextWriter;
+                if (bufferedWriter == null)
                 {
-                    if (executeViewStart)
-                    {
-                        // Execute view starts using the same context + writer as the page to render.
-                        await RenderViewStartAsync(context);
-                    }
+                    var message = Resources.FormatInstrumentation_WriterMustBeBufferedTextWriter(
+                        nameof(TextWriter),
+                        _pageExecutionFeature.GetType().FullName,
+                        typeof(IBufferedTextWriter).FullName);
+                    throw new InvalidOperationException(message);
+                }
+            }
 
-                    await RenderPageCoreAsync(page, context);
-                    return bufferedWriter;
-                }
-                finally
+            // The writer for the body is passed through the ViewContext, allowing things like HtmlHelpers
+            // and ViewComponents to reference it.
+            var oldWriter = context.Writer;
+            context.Writer = writer;
+
+            try
+            {
+                if (executeViewStart)
                 {
-                    context.Writer = oldWriter;
+                    // Execute view starts using the same context + writer as the page to render.
+                    await RenderViewStartAsync(context);
                 }
+
+                await RenderPageCoreAsync(page, context);
+                return bufferedWriter;
+            }
+            finally
+            {
+                context.Writer = oldWriter;
+                writer.Dispose();
             }
         }
 
         private async Task RenderPageCoreAsync(IRazorPage page, ViewContext context)
         {
             page.ViewContext = context;
+            if (EnableInstrumentation)
+            {
+                page.PageExecutionContext = _pageExecutionFeature.GetContext(page.Path, context.Writer);
+            }
+
             _pageActivator.Activate(page, context);
             await page.ExecuteAsync();
         }
 
         private async Task RenderViewStartAsync(ViewContext context)
         {
-            var viewStarts = _viewStartProvider.GetViewStartPages(_razorPage.Path);
+            var viewStarts = _viewStartProvider.GetViewStartPages(_razorPage.Path, EnableInstrumentation);
 
             foreach (var viewStart in viewStarts)
             {
@@ -111,7 +143,7 @@ namespace Microsoft.AspNet.Mvc.Razor
         }
 
         private async Task RenderLayoutAsync(ViewContext context,
-                                             RazorTextWriter bodyWriter)
+                                             IBufferedTextWriter bodyWriter)
         {
             // A layout page can specify another layout page. We'll need to continue
             // looking for layout pages until they're no longer specified.
@@ -129,7 +161,7 @@ namespace Microsoft.AspNet.Mvc.Razor
                     throw new InvalidOperationException(message);
                 }
 
-                var layoutPage = _pageFactory.CreateInstance(previousPage.Layout);
+                var layoutPage = _pageFactory.CreateInstance(previousPage.Layout, EnableInstrumentation);
                 if (layoutPage == null)
                 {
                     var message = Resources.FormatLayoutCannotBeLocated(previousPage.Layout);

src/Microsoft.AspNet.Mvc.Razor/RazorViewEngine.cs

@@ -3,9 +3,11 @@
 
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Globalization;
 using Microsoft.AspNet.Mvc.Razor.OptionDescriptors;
 using Microsoft.AspNet.Mvc.Rendering;
+using Microsoft.AspNet.PageExecutionInstrumentation;
 using Microsoft.Framework.DependencyInjection;
 
 namespace Microsoft.AspNet.Mvc.Razor
@@ -35,6 +37,9 @@ namespace Microsoft.AspNet.Mvc.Razor
         private readonly IRazorPageFactory _pageFactory;
         private readonly IReadOnlyList<IViewLocationExpander> _viewLocationExpanders;
         private readonly IViewLocationCache _viewLocationCache;
+        // The RazorViewEngine is Request scoped which allows us to cache these value for the lifetime of a Request.
+        private bool _isPageExecutionFeatureInitialized;
+        private IPageExecutionListenerFeature _pageExecutionListenerFeature;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="RazorViewEngine" /> class.
@@ -90,7 +95,7 @@ namespace Microsoft.AspNet.Mvc.Razor
             {
                 if (viewName.EndsWith(ViewExtension, StringComparison.OrdinalIgnoreCase))
                 {
-                    var page = _pageFactory.CreateInstance(viewName);
+                    var page = _pageFactory.CreateInstance(viewName, IsInstrumentationEnabled(context));
                     if (page != null)
                     {
                         return CreateFoundResult(context, page, viewName, partial);
@@ -132,7 +137,7 @@ namespace Microsoft.AspNet.Mvc.Razor
             var viewLocation = _viewLocationCache.Get(expanderContext);
             if (!string.IsNullOrEmpty(viewLocation))
             {
-                var page = _pageFactory.CreateInstance(viewLocation);
+                var page = _pageFactory.CreateInstance(viewLocation, IsInstrumentationEnabled(context));
 
                 if (page != null)
                 {
@@ -158,7 +163,7 @@ namespace Microsoft.AspNet.Mvc.Razor
                                                     viewName,
                                                     controllerName,
                                                     areaName);
-                var page = _pageFactory.CreateInstance(transformedPath);
+                var page = _pageFactory.CreateInstance(transformedPath, IsInstrumentationEnabled(context));
                 if (page != null)
                 {
                     // 3a. We found a page. Cache the set of values that produced it and return a found result.
@@ -183,7 +188,9 @@ namespace Microsoft.AspNet.Mvc.Razor
 
             var services = actionContext.HttpContext.RequestServices;
             var view = services.GetService<IRazorView>();
-            view.Contextualize(page, partial);
+            Debug.Assert(_isPageExecutionFeatureInitialized, "IsInstrumentationEnabled must be called prior to this.");
+
+            view.Contextualize(page, partial, _pageExecutionListenerFeature);
             return ViewEngineResult.Found(viewName, view);
         }
 
@@ -191,5 +198,16 @@ namespace Microsoft.AspNet.Mvc.Razor
         {
             return name[0] == '~' || name[0] == '/';
         }
+
+        private bool IsInstrumentationEnabled(ActionContext context)
+        {
+            if (!_isPageExecutionFeatureInitialized)
+            {
+                _isPageExecutionFeatureInitialized = true;
+                _pageExecutionListenerFeature = context.HttpContext.GetFeature<IPageExecutionListenerFeature>();
+            }
+
+            return _pageExecutionListenerFeature != null;
+        }
     }
 }

src/Microsoft.AspNet.Mvc.Razor/ViewStartProvider.cs

@@ -22,14 +22,13 @@ namespace Microsoft.AspNet.Mvc.Razor
             _pageFactory = pageFactory;
         }
 
-
         /// <inheritdoc />
-        public IEnumerable<IRazorPage> GetViewStartPages([NotNull] string path)
+        public IEnumerable<IRazorPage> GetViewStartPages([NotNull] string path, bool enableInstrumentation)
         {
             var viewStartLocations = ViewStartUtility.GetViewStartLocations(_fileSystem, path);
-            var viewStarts = viewStartLocations.Select(_pageFactory.CreateInstance)
-                                                .Where(p => p != null)
-                                                .ToArray();
+            var viewStarts = viewStartLocations.Select(p => _pageFactory.CreateInstance(p, enableInstrumentation))
+                                               .Where(p => p != null)
+                                               .ToArray();
 
             // GetViewStartLocations return ViewStarts inside-out that is the _ViewStart closest to the page 
             // is the first: e.g. [ /Views/Home/_ViewStart, /Views/_ViewStart, /_ViewStart ]

src/Microsoft.AspNet.Mvc.Razor/VirtualPathRazorPageFactory.cs

@@ -30,7 +30,7 @@ namespace Microsoft.AspNet.Mvc.Razor
         }
 
         /// <inheritdoc />
-        public IRazorPage CreateInstance([NotNull] string relativePath)
+        public IRazorPage CreateInstance([NotNull] string relativePath, bool enableInstrumentation)
         {
             var fileInfo = _fileInfoCache.GetFileInfo(relativePath);
 
@@ -42,7 +42,7 @@ namespace Microsoft.AspNet.Mvc.Razor
                     RelativePath = relativePath,
                 };
 
-                var result = _compilationService.Compile(relativeFileInfo);
+                var result = _compilationService.Compile(relativeFileInfo, enableInstrumentation);
                 var page = (IRazorPage)_activator.CreateInstance(_serviceProvider, result.CompiledType);
                 page.Path = relativePath;
 

src/Microsoft.AspNet.Mvc/MvcServices.cs

@@ -2,7 +2,6 @@
 // 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.Mvc.Core;
 using Microsoft.AspNet.Mvc.Description;
 using Microsoft.AspNet.Mvc.Filters;
 using Microsoft.AspNet.Mvc.Internal;
@@ -49,7 +48,10 @@ namespace Microsoft.AspNet.Mvc
 
             yield return describe.Singleton<ICompilationService, RoslynCompilationService>();
             yield return describe.Singleton<IRazorCompilationService, RazorCompilationService>();
-            yield return describe.Singleton<IViewEngineProvider, DefaultViewEngineProvider>();
+
+            // The provider is inexpensive to initialize and provides ViewEngines that may require request
+            // specific services.
+            yield return describe.Transient<IViewEngineProvider, DefaultViewEngineProvider>();
             yield return describe.Scoped<ICompositeViewEngine, CompositeViewEngine>();
             yield return describe.Singleton<IViewStartProvider, ViewStartProvider>();
             yield return describe.Transient<IRazorView, RazorView>();

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

@@ -0,0 +1,154 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using Microsoft.AspNet.Builder;
+using Microsoft.AspNet.TestHost;
+using Microsoft.Framework.DependencyInjection;
+using Microsoft.Framework.DependencyInjection.Fallback;
+using RazorInstrumentationWebSite;
+using Xunit;
+
+namespace Microsoft.AspNet.Mvc.FunctionalTests
+{
+    public class RazorInstrumentationTests
+    {
+        private readonly IServiceProvider _services = TestHelper.CreateServices("RazorInstrumentationWebsite");
+        private readonly Action<IApplicationBuilder> _app = new Startup().Configure;
+        private readonly string _expected = string.Join(Environment.NewLine,
+                                                        @"<div>",
+                                                        @"2147483647",
+                                                        "",
+                                                        @"viewstart-content",
+                                                        @"<p class=""Hello world"">",
+                                                        @"page-content",
+                                                        @"</p>",
+                                                        @"</div>");
+        private readonly IEnumerable<Tuple<int, int, bool>> _expectedLineMappings = new[]
+        {
+            Tuple.Create(93, 2, true),
+            Tuple.Create(96, 16, false),
+            Tuple.Create(112, 2, true),
+            Tuple.Create(0, 2, true),
+            Tuple.Create(2, 8, true),
+            Tuple.Create(10, 16, false),
+            Tuple.Create(26, 1, true),
+            Tuple.Create(27, 21, true),
+            Tuple.Create(0, 7, true),
+            Tuple.Create(8, 12, false),
+            Tuple.Create(20, 2, true),
+            Tuple.Create(23, 12, false),
+            Tuple.Create(35, 8, true),
+        };
+
+        public static IEnumerable<object[]> ActionNames
+        {
+            get
+            {
+                yield return new[] { "FullPath" };
+                yield return new[] { "ViewDiscoveryPath" };
+            }
+        }
+
+        [Theory]
+        [MemberData(nameof(ActionNames))]
+        public async Task ViewsAreServedWithoutInstrumentationByDefault(string actionName)
+        {
+            // Arrange
+            var context = new TestPageExecutionContext();
+            var services = GetServiceProvider(context);
+            var server = TestServer.Create(services, _app);
+            var client = server.CreateClient();
+
+            // Act
+            var body = await client.GetStringAsync("http://localhost/Home/" + actionName);
+
+            // Assert
+            Assert.Equal(_expected, body.Trim());
+            Assert.Empty(context.Values);
+        }
+
+        [Theory]
+        [MemberData(nameof(ActionNames))]
+        public async Task ViewsAreInstrumentedWhenPageExecutionListenerFeatureIsEnabled(string actionName)
+        {
+            // Arrange
+            var context = new TestPageExecutionContext();
+            var services = GetServiceProvider(context);
+            var server = TestServer.Create(services, _app);
+            var client = server.CreateClient();
+            client.DefaultRequestHeaders.Add("ENABLE-RAZOR-INSTRUMENTATION", "true");
+
+            // Act
+            var body = await client.GetStringAsync("http://localhost/Home/" + actionName);
+
+            // Assert
+            Assert.Equal(_expected, body.Trim());
+            Assert.Equal(_expectedLineMappings, context.Values);
+        }
+
+        [Theory]
+        [MemberData(nameof(ActionNames))]
+        public async Task ViewsCanSwitchFromRegularToInstrumented(string actionName)
+        {
+            // Arrange - 1
+            var context = new TestPageExecutionContext();
+            var services = GetServiceProvider(context);
+            var server = TestServer.Create(services, _app);
+            var client = server.CreateClient();
+
+            // Act - 1
+            var body = await client.GetStringAsync("http://localhost/Home/" + actionName);
+
+            // Assert - 1
+            Assert.Equal(_expected, body.Trim());
+            Assert.Empty(context.Values);
+
+            // Arrange - 2
+            client.DefaultRequestHeaders.Add("ENABLE-RAZOR-INSTRUMENTATION", "true");
+
+            // Act - 2
+            body = await client.GetStringAsync("http://localhost/Home/" + actionName);
+
+            // Assert - 2
+            Assert.Equal(_expected, body.Trim());
+            Assert.Equal(_expectedLineMappings, context.Values);
+        }
+
+        [Fact]
+        public async Task SwitchingFromNonInstrumentedToInstrumentedWorksForLayoutAndViewStarts()
+        {
+            // Arrange - 1
+            var context = new TestPageExecutionContext();
+            var services = GetServiceProvider(context);
+            var server = TestServer.Create(services, _app);
+            var client = server.CreateClient();
+
+            // Act - 1
+            var body = await client.GetStringAsync("http://localhost/Home/FullPath");
+
+            // Assert - 1
+            Assert.Equal(_expected, body.Trim());
+            Assert.Empty(context.Values);
+
+            // Arrange - 2
+            client.DefaultRequestHeaders.Add("ENABLE-RAZOR-INSTRUMENTATION", "true");
+
+            // Act - 2
+            body = await client.GetStringAsync("http://localhost/Home/ViewDiscoveryPath");
+
+            // Assert - 2
+            Assert.Equal(_expected, body.Trim());
+            Assert.Equal(_expectedLineMappings, context.Values);
+        }
+
+        private IServiceProvider GetServiceProvider(TestPageExecutionContext pageExecutionContext)
+        {
+            var services = new ServiceCollection();
+            services.AddInstance(pageExecutionContext);
+            return services.BuildServiceProvider(_services);
+        }
+    }
+}

test/Microsoft.AspNet.Mvc.FunctionalTests/project.json

@@ -28,6 +28,7 @@
         "ReflectedModelWebSite": "",
         "RoutingWebSite": "",
         "RazorWebSite": "",
+        "RazorInstrumentationWebsite": "",
         "ValueProvidersSite": "",
         "XmlSerializerWebSite": "",
         "UrlHelperWebSite": "",

test/Microsoft.AspNet.Mvc.Razor.Test/Compilation/CompilerCacheTest.cs

@@ -34,7 +34,7 @@ namespace Microsoft.AspNet.Mvc.Razor.Test
             };
 
             // Act
-            var actual = cache.GetOrAdd(runtimeFileInfo, () => expected);
+            var actual = cache.GetOrAdd(runtimeFileInfo, false, () => expected);
 
             // Assert
             Assert.Same(expected, actual);
@@ -140,7 +140,8 @@ namespace Microsoft.AspNet.Mvc.Razor.Test
 
             // Act
             var actual = cache.GetOrAdd(runtimeFileInfo,
-                () => CompilationResult.Successful(resultViewType));
+                                        enableInstrumentation: false,
+                                        compile: () => CompilationResult.Successful(resultViewType));
 
             // Assert
             if (swapsPreCompile)
@@ -174,9 +175,9 @@ namespace Microsoft.AspNet.Mvc.Razor.Test
             };
 
             // Act
-            cache.GetOrAdd(runtimeFileInfo, () => uncachedResult);
-            var actual1 = cache.GetOrAdd(runtimeFileInfo, () => uncachedResult);
-            var actual2 = cache.GetOrAdd(runtimeFileInfo, () => uncachedResult);
+            cache.GetOrAdd(runtimeFileInfo, false, () => uncachedResult);
+            var actual1 = cache.GetOrAdd(runtimeFileInfo, false, () => uncachedResult);
+            var actual2 = cache.GetOrAdd(runtimeFileInfo, false, () => uncachedResult);
 
             // Assert
             Assert.NotSame(uncachedResult, actual1);
@@ -189,5 +190,40 @@ namespace Microsoft.AspNet.Mvc.Razor.Test
             Assert.Null(actual2.CompiledContent);
             Assert.Same(type, actual2.CompiledType);
         }
+
+        [Fact]
+        public void GetOrAdd_IgnoresCache_IfCachedItemIsNotInstrumentedAndEnableInstrumentationIsTrue()
+        {
+            // Arrange
+            var lastModified = DateTime.UtcNow;
+            var cache = new CompilerCache();
+            var fileInfo = new Mock<IFileInfo>();
+            fileInfo.SetupGet(f => f.PhysicalPath)
+                    .Returns("test");
+            fileInfo.SetupGet(f => f.LastModified)
+                    .Returns(lastModified);
+            var type = GetType();
+            var uncachedResult1 = UncachedCompilationResult.Successful(type, "hello world");
+            var uncachedResult2 = UncachedCompilationResult.Successful(typeof(object), "hello world");
+            var uncachedResult3 = UncachedCompilationResult.Successful(typeof(Guid), "hello world");
+
+            var runtimeFileInfo = new RelativeFileInfo()
+            {
+                FileInfo = fileInfo.Object,
+                RelativePath = "test",
+            };
+
+            // Act
+            cache.GetOrAdd(runtimeFileInfo, false, () => uncachedResult1);
+            var actual1 = cache.GetOrAdd(runtimeFileInfo, true, () => uncachedResult2);
+            var actual2 = cache.GetOrAdd(runtimeFileInfo, false, () => uncachedResult3);
+
+            // Assert
+            Assert.Same(uncachedResult2, actual1);
+            Assert.Same(typeof(object), actual1.CompiledType);
+
+            Assert.NotSame(actual2, uncachedResult3);
+            Assert.Same(typeof(object), actual2.CompiledType);
+        }
     }
 }

test/Microsoft.AspNet.Mvc.Razor.Test/RazorCompilationServiceTest.cs

@@ -23,7 +23,7 @@ namespace Microsoft.AspNet.Mvc.Razor.Test
             // Arrange
             var host = new Mock<IMvcRazorHost>();
             host.Setup(h => h.GenerateCode(@"views\index\home.cshtml", It.IsAny<Stream>()))
-                .Returns(new GeneratorResults(new Block(new BlockBuilder { Type = BlockType.Comment }), new RazorError[0], new CodeBuilderResult("", new LineMapping[0])))
+                .Returns(GetGeneratorResult())
                 .Verifiable();
 
             var ap = new Mock<IControllerAssemblyProvider>();
@@ -46,10 +46,51 @@ namespace Microsoft.AspNet.Mvc.Razor.Test
             };
 
             // Act
-            razorService.CompileCore(relativeFileInfo);
+            razorService.CompileCore(relativeFileInfo, isInstrumented: false);
 
             // Assert
             host.Verify();
         }
+
+        [Theory]
+        [InlineData(false)]
+        [InlineData(true)]
+        public void CompileCoreSetsEnableInstrumentationOnHost(bool enableInstrumentation)
+        {
+            // Arrange
+            var host = new Mock<IMvcRazorHost>();
+            host.SetupAllProperties();
+            host.Setup(h => h.GenerateCode(It.IsAny<string>(), It.IsAny<Stream>()))
+                .Returns(GetGeneratorResult());
+            var assemblyProvider = new Mock<IControllerAssemblyProvider>();
+            assemblyProvider.SetupGet(e => e.CandidateAssemblies)
+                            .Returns(Enumerable.Empty<Assembly>());
+
+            var compiler = new Mock<ICompilationService>();
+            compiler.Setup(c => c.Compile(It.IsAny<IFileInfo>(), It.IsAny<string>()))
+                    .Returns(CompilationResult.Successful(GetType()));
+
+            var razorService = new RazorCompilationService(compiler.Object, assemblyProvider.Object, host.Object);
+            var relativeFileInfo = new RelativeFileInfo()
+            {
+                FileInfo = Mock.Of<IFileInfo>(),
+                RelativePath = @"views\index\home.cshtml",
+            };
+
+            // Act
+            razorService.CompileCore(relativeFileInfo, isInstrumented: enableInstrumentation);
+
+            // Assert
+            Assert.Equal(enableInstrumentation, host.Object.EnableInstrumentation);
+        }
+
+        private static GeneratorResults GetGeneratorResult()
+        {
+            return new GeneratorResults(
+                    new Block(
+                        new BlockBuilder { Type = BlockType.Comment }),
+                        new RazorError[0],
+                        new CodeBuilderResult("", new LineMapping[0]));
+        }
     }
 }

test/Microsoft.AspNet.Mvc.Razor.Test/RazorViewEngineTest.cs

@@ -183,7 +183,7 @@ namespace Microsoft.AspNet.Mvc.Razor.Test
             // Arrange
             var pageFactory = new Mock<IRazorPageFactory>();
             var page = Mock.Of<IRazorPage>();
-            pageFactory.Setup(p => p.CreateInstance(It.IsAny<string>()))
+            pageFactory.Setup(p => p.CreateInstance(It.IsAny<string>(), false))
                        .Returns(Mock.Of<IRazorPage>());
             var viewEngine = CreateViewEngine(pageFactory.Object);
             var context = GetActionContext(_controllerTestContext);
@@ -203,7 +203,7 @@ namespace Microsoft.AspNet.Mvc.Razor.Test
             // Arrange
             var pageFactory = new Mock<IRazorPageFactory>();
             var page = Mock.Of<IRazorPage>();
-            pageFactory.Setup(p => p.CreateInstance("fake-path1/bar/test-view.rzr"))
+            pageFactory.Setup(p => p.CreateInstance("fake-path1/bar/test-view.rzr", false))
                        .Returns(Mock.Of<IRazorPage>())
                        .Verifiable();
             var viewEngine = new OverloadedLocationViewEngine(pageFactory.Object,
@@ -224,7 +224,7 @@ namespace Microsoft.AspNet.Mvc.Razor.Test
             // Arrange
             var pageFactory = new Mock<IRazorPageFactory>();
             var page = Mock.Of<IRazorPage>();
-            pageFactory.Setup(p => p.CreateInstance("fake-area-path/foo/bar/test-view2.rzr"))
+            pageFactory.Setup(p => p.CreateInstance("fake-area-path/foo/bar/test-view2.rzr", false))
                        .Returns(Mock.Of<IRazorPage>())
                        .Verifiable();
             var viewEngine = new OverloadedLocationViewEngine(pageFactory.Object,
@@ -273,7 +273,7 @@ namespace Microsoft.AspNet.Mvc.Razor.Test
         {
             // Arrange
             var pageFactory = new Mock<IRazorPageFactory>();
-            pageFactory.Setup(p => p.CreateInstance("test-string/bar.cshtml"))
+            pageFactory.Setup(p => p.CreateInstance("test-string/bar.cshtml", false))
                        .Returns(Mock.Of<IRazorPage>())
                        .Verifiable();
             var expander1Result = new[] { "some-seed" };
@@ -325,9 +325,9 @@ namespace Microsoft.AspNet.Mvc.Razor.Test
         {
             // Arrange
             var pageFactory = new Mock<IRazorPageFactory>();
-            pageFactory.Setup(p => p.CreateInstance("/Views/bar/baz.cshtml"))
+            pageFactory.Setup(p => p.CreateInstance("/Views/bar/baz.cshtml", false))
                        .Verifiable();
-            pageFactory.Setup(p => p.CreateInstance("/Views/Shared/baz.cshtml"))
+            pageFactory.Setup(p => p.CreateInstance("/Views/Shared/baz.cshtml", false))
                        .Returns(Mock.Of<IRazorPage>())
                        .Verifiable();
             var cache = GetViewLocationCache();
@@ -353,7 +353,7 @@ namespace Microsoft.AspNet.Mvc.Razor.Test
         {
             // Arrange
             var pageFactory = new Mock<IRazorPageFactory>(MockBehavior.Strict);
-            pageFactory.Setup(p => p.CreateInstance("some-view-location"))
+            pageFactory.Setup(p => p.CreateInstance("some-view-location", false))
                        .Returns(Mock.Of<IRazorPage>())
                        .Verifiable();
             var expander = new Mock<IViewLocationExpander>(MockBehavior.Strict);
@@ -384,10 +384,10 @@ namespace Microsoft.AspNet.Mvc.Razor.Test
         {
             // Arrange
             var pageFactory = new Mock<IRazorPageFactory>();
-            pageFactory.Setup(p => p.CreateInstance("expired-location"))
+            pageFactory.Setup(p => p.CreateInstance("expired-location", false))
                        .Returns((IRazorPage)null)
                        .Verifiable();
-            pageFactory.Setup(p => p.CreateInstance("some-view-location"))
+            pageFactory.Setup(p => p.CreateInstance("some-view-location", false))
                        .Returns(Mock.Of<IRazorPage>())
                        .Verifiable();
             var cacheMock = new Mock<IViewLocationCache>();

test/Microsoft.AspNet.Mvc.Razor.Test/RazorViewTest.cs

@@ -3,8 +3,10 @@
 
 using System;
 using System.IO;
+using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.AspNet.Mvc.ModelBinding;
+using Microsoft.AspNet.PageExecutionInstrumentation;
 using Microsoft.AspNet.PipelineCore;
 using Moq;
 using Xunit;
@@ -45,7 +47,7 @@ namespace Microsoft.AspNet.Mvc.Razor
             var view = new RazorView(Mock.Of<IRazorPageFactory>(),
                                      Mock.Of<IRazorPageActivator>(),
                                      CreateViewStartProvider());
-            view.Contextualize(page, isPartial: true);
+            view.Contextualize(page, isPartial: true, pageExecutionListener: null);
             var viewContext = CreateViewContext(view);
             var expected = viewContext.Writer;
 
@@ -72,7 +74,7 @@ namespace Microsoft.AspNet.Mvc.Razor
             var view = new RazorView(Mock.Of<IRazorPageFactory>(),
                                      activator.Object,
                                      CreateViewStartProvider());
-            view.Contextualize(page, isPartial: true);
+            view.Contextualize(page, isPartial: true, pageExecutionListener: null);
             var viewContext = CreateViewContext(view);
             var expectedWriter = viewContext.Writer;
             activator.Setup(a => a.Activate(page, It.IsAny<ViewContext>()))
@@ -102,7 +104,7 @@ namespace Microsoft.AspNet.Mvc.Razor
             var view = new RazorView(Mock.Of<IRazorPageFactory>(),
                                      activator.Object,
                                      CreateViewStartProvider());
-            view.Contextualize(page, isPartial: true);
+            view.Contextualize(page, isPartial: true, pageExecutionListener: null);
             var viewContext = CreateViewContext(view);
 
             // Act
@@ -124,15 +126,16 @@ namespace Microsoft.AspNet.Mvc.Razor
             var view = new RazorView(pageFactory.Object,
                                      Mock.Of<IRazorPageActivator>(),
                                      viewStartProvider);
-            view.Contextualize(page, isPartial: true);
+            view.Contextualize(page, isPartial: true, pageExecutionListener: null);
             var viewContext = CreateViewContext(view);
 
             // Act
             await view.RenderAsync(viewContext);
 
             // Assert
-            pageFactory.Verify(v => v.CreateInstance(It.IsAny<string>()), Times.Never());
-            Mock.Get(viewStartProvider).Verify(v => v.GetViewStartPages(It.IsAny<string>()), Times.Never());
+            pageFactory.Verify(v => v.CreateInstance(It.IsAny<string>(), It.IsAny<bool>()), Times.Never());
+            Mock.Get(viewStartProvider)
+                .Verify(v => v.GetViewStartPages(It.IsAny<string>(), It.IsAny<bool>()), Times.Never());
         }
 
         [Fact]
@@ -147,7 +150,7 @@ namespace Microsoft.AspNet.Mvc.Razor
             var view = new RazorView(Mock.Of<IRazorPageFactory>(),
                                      Mock.Of<IRazorPageActivator>(),
                                      CreateViewStartProvider());
-            view.Contextualize(page, isPartial: false);
+            view.Contextualize(page, isPartial: false, pageExecutionListener: null);
             var viewContext = CreateViewContext(view);
             var original = viewContext.Writer;
 
@@ -170,7 +173,7 @@ namespace Microsoft.AspNet.Mvc.Razor
             var view = new RazorView(Mock.Of<IRazorPageFactory>(),
                                      Mock.Of<IRazorPageActivator>(),
                                      CreateViewStartProvider());
-            view.Contextualize(page, isPartial: false);
+            view.Contextualize(page, isPartial: false, pageExecutionListener: null);
             var viewContext = CreateViewContext(view);
             var original = viewContext.Writer;
 
@@ -195,7 +198,7 @@ namespace Microsoft.AspNet.Mvc.Razor
             var view = new RazorView(Mock.Of<IRazorPageFactory>(),
                                      activator.Object,
                                      CreateViewStartProvider());
-            view.Contextualize(page, isPartial: false);
+            view.Contextualize(page, isPartial: false, pageExecutionListener: null);
 
             var viewContext = CreateViewContext(view);
 
@@ -237,7 +240,7 @@ namespace Microsoft.AspNet.Mvc.Razor
             var view = new RazorView(Mock.Of<IRazorPageFactory>(),
                                      activator.Object,
                                      CreateViewStartProvider(viewStart1, viewStart2));
-            view.Contextualize(page, isPartial: false);
+            view.Contextualize(page, isPartial: false, pageExecutionListener: null);
             var viewContext = CreateViewContext(view);
 
             // Act
@@ -285,13 +288,13 @@ foot-content";
             activator.Setup(a => a.Activate(layout, It.IsAny<ViewContext>()))
                      .Verifiable();
             var pageFactory = new Mock<IRazorPageFactory>();
-            pageFactory.Setup(p => p.CreateInstance(LayoutPath))
+            pageFactory.Setup(p => p.CreateInstance(LayoutPath, false))
                        .Returns(layout);
 
             var view = new RazorView(pageFactory.Object,
                                      activator.Object,
                                      CreateViewStartProvider());
-            view.Contextualize(page, isPartial: false);
+            view.Contextualize(page, isPartial: false, pageExecutionListener: null);
             var viewContext = CreateViewContext(view);
 
             // Act
@@ -318,13 +321,13 @@ foot-content";
                 v.RenderBodyPublic();
             });
             var pageFactory = new Mock<IRazorPageFactory>();
-            pageFactory.Setup(p => p.CreateInstance(LayoutPath))
+            pageFactory.Setup(p => p.CreateInstance(LayoutPath, false))
                        .Returns(layout);
 
             var view = new RazorView(pageFactory.Object,
                                      Mock.Of<IRazorPageActivator>(),
                                      CreateViewStartProvider());
-            view.Contextualize(page, isPartial: false);
+            view.Contextualize(page, isPartial: false, pageExecutionListener: null);
             var viewContext = CreateViewContext(view);
 
             // Act and Assert
@@ -344,13 +347,13 @@ foot-content";
             {
             });
             var pageFactory = new Mock<IRazorPageFactory>();
-            pageFactory.Setup(p => p.CreateInstance(LayoutPath))
+            pageFactory.Setup(p => p.CreateInstance(LayoutPath, false))
                        .Returns(layout);
 
             var view = new RazorView(pageFactory.Object,
                                      Mock.Of<IRazorPageActivator>(),
                                      CreateViewStartProvider());
-            view.Contextualize(page, isPartial: false);
+            view.Contextualize(page, isPartial: false, pageExecutionListener: null);
             var viewContext = CreateViewContext(view);
 
             // Act and Assert
@@ -396,15 +399,15 @@ body-content";
                 v.RenderBodyPublic();
             });
             var pageFactory = new Mock<IRazorPageFactory>();
-            pageFactory.Setup(p => p.CreateInstance("~/Shared/Layout1.cshtml"))
+            pageFactory.Setup(p => p.CreateInstance("~/Shared/Layout1.cshtml", false))
                        .Returns(layout1);
-            pageFactory.Setup(p => p.CreateInstance("~/Shared/Layout2.cshtml"))
+            pageFactory.Setup(p => p.CreateInstance("~/Shared/Layout2.cshtml", false))
                        .Returns(layout2);
 
             var view = new RazorView(pageFactory.Object,
                                      Mock.Of<IRazorPageActivator>(),
                                      CreateViewStartProvider());
-            view.Contextualize(page, isPartial: false);
+            view.Contextualize(page, isPartial: false, pageExecutionListener: null);
             var viewContext = CreateViewContext(view);
 
             // Act
@@ -444,13 +447,13 @@ section-content-2";
             });
 
             var pageFactory = new Mock<IRazorPageFactory>();
-            pageFactory.Setup(p => p.CreateInstance("layout-1"))
+            pageFactory.Setup(p => p.CreateInstance("layout-1", false))
                        .Returns(layout1);
 
             var view = new RazorView(pageFactory.Object,
                                      Mock.Of<IRazorPageActivator>(),
                                      CreateViewStartProvider());
-            view.Contextualize(page, isPartial: false);
+            view.Contextualize(page, isPartial: false, pageExecutionListener: null);
             var viewContext = CreateViewContext(view);
 
             // Act
@@ -488,13 +491,13 @@ section-content-2";
             });
 
             var pageFactory = new Mock<IRazorPageFactory>();
-            pageFactory.Setup(p => p.CreateInstance("layout-1"))
+            pageFactory.Setup(p => p.CreateInstance("layout-1", false))
                        .Returns(layout1);
 
             var view = new RazorView(pageFactory.Object,
                                      Mock.Of<IRazorPageActivator>(),
                                      CreateViewStartProvider());
-            view.Contextualize(page, isPartial: false);
+            view.Contextualize(page, isPartial: false, pageExecutionListener: null);
             var viewContext = CreateViewContext(view);
 
             // Act
@@ -520,7 +523,7 @@ section-content-2";
             var view = new RazorView(Mock.Of<IRazorPageFactory>(),
                                      Mock.Of<IRazorPageActivator>(),
                                      CreateViewStartProvider());
-            view.Contextualize(page, isPartial: false);
+            view.Contextualize(page, isPartial: false, pageExecutionListener: null);
             var viewContext = CreateViewContext(view);
 
             // Act and Assert
@@ -555,13 +558,13 @@ section-content-2";
                 v.Layout = "~/Shared/Layout2.cshtml";
             });
             var pageFactory = new Mock<IRazorPageFactory>();
-            pageFactory.Setup(p => p.CreateInstance("~/Shared/Layout1.cshtml"))
+            pageFactory.Setup(p => p.CreateInstance("~/Shared/Layout1.cshtml", false))
                        .Returns(layout1);
 
             var view = new RazorView(pageFactory.Object,
                                      Mock.Of<IRazorPageActivator>(),
                                      CreateViewStartProvider());
-            view.Contextualize(page, isPartial: false);
+            view.Contextualize(page, isPartial: false, pageExecutionListener: null);
             var viewContext = CreateViewContext(view);
 
             // Act and Assert
@@ -569,6 +572,153 @@ section-content-2";
             Assert.Equal(expected, ex.Message);
         }
 
+        [Fact]
+        public async Task RenderAsync_UsesPageExecutionFeatureFromRequest_ToWrapWriter()
+        {
+            // Arrange
+            var pageWriter = CreateBufferedWriter();
+            var layoutWriter = CreateBufferedWriter();
+
+            var layoutExecuted = false;
+            var count = -1;
+            var feature = new Mock<IPageExecutionListenerFeature>(MockBehavior.Strict);
+            feature.Setup(f => f.DecorateWriter(It.IsAny<RazorTextWriter>()))
+                   .Returns(() =>
+                   {
+                       count++;
+                       if (count == 0)
+                       {
+                           return pageWriter;
+                       }
+                       else if (count == 1)
+                       {
+                           return layoutWriter;
+                       }
+                       throw new Exception();
+                   })
+                   .Verifiable();
+
+            var pageContext = Mock.Of<IPageExecutionContext>();
+            feature.Setup(f => f.GetContext("/MyPage.cshtml", pageWriter))
+                    .Returns(pageContext)
+                    .Verifiable();
+
+            var layoutContext = Mock.Of<IPageExecutionContext>();
+            feature.Setup(f => f.GetContext("/Layout.cshtml", layoutWriter))
+                    .Returns(layoutContext)
+                    .Verifiable();
+
+            var page = new TestableRazorPage(v =>
+            {
+                v.Layout = "/Layout.cshtml";
+                Assert.Same(pageWriter, v.Output);
+                Assert.Same(pageContext, v.PageExecutionContext);
+            });
+            page.Path = "/MyPage.cshtml";
+
+            var layout = new TestableRazorPage(v =>
+            {
+                Assert.Same(layoutWriter, v.Output);
+                Assert.Same(layoutContext, v.PageExecutionContext);
+                v.RenderBodyPublic();
+
+                layoutExecuted = true;
+            });
+            layout.Path = "/Layout.cshtml";
+
+            var pageFactory = new Mock<IRazorPageFactory>();
+            pageFactory.Setup(p => p.CreateInstance("/Layout.cshtml", true))
+                       .Returns(layout);
+            var viewStartProvider = new Mock<IViewStartProvider>();
+            viewStartProvider.Setup(v => v.GetViewStartPages(It.IsAny<string>(), true))
+                             .Returns(Enumerable.Empty<IRazorPage>())
+                             .Verifiable();
+            var view = new RazorView(pageFactory.Object,
+                                     Mock.Of<IRazorPageActivator>(),
+                                     viewStartProvider.Object);
+            view.Contextualize(page, isPartial: false, pageExecutionListener: feature.Object);
+            var viewContext = CreateViewContext(view);
+
+            // Act
+            await view.RenderAsync(viewContext);
+
+            // Assert
+            feature.Verify();
+            viewStartProvider.Verify();
+            Assert.True(layoutExecuted);
+        }
+
+        [Fact]
+        public async Task RenderAsync_UsesPageExecutionFeatureFromRequest_ToGetExecutionContext()
+        {
+            // Arrange
+            var writer = Mock.Of<TextWriter>();
+            var executed = false;
+            var feature = new Mock<IPageExecutionListenerFeature>(MockBehavior.Strict);
+
+            var pageContext = Mock.Of<IPageExecutionContext>();
+            feature.Setup(f => f.GetContext("/MyPartialPage.cshtml", writer))
+                    .Returns(pageContext)
+                    .Verifiable();
+
+            var page = new TestableRazorPage(v =>
+            {
+                Assert.Same(writer, v.Output);
+                Assert.Same(pageContext, v.PageExecutionContext);
+                executed = true;
+            });
+            page.Path = "/MyPartialPage.cshtml";
+
+            var view = new RazorView(Mock.Of<IRazorPageFactory>(),
+                                     Mock.Of<IRazorPageActivator>(),
+                                     Mock.Of<IViewStartProvider>());
+            view.Contextualize(page, isPartial: true, pageExecutionListener: feature.Object);
+            var viewContext = CreateViewContext(view);
+            viewContext.Writer = writer;
+
+            // Act
+            await view.RenderAsync(viewContext);
+
+            // Assert
+            feature.Verify();
+            Assert.True(executed);
+        }
+
+        [Theory]
+        [InlineData(false)]
+        [InlineData(true)]
+        public async Task RenderAsync_DoesNotSetExecutionContextWhenListenerIsNotRegistered(bool isPartial)
+        {
+            // Arrange
+            var executed = false;
+            var page = new TestableRazorPage(v =>
+            {
+                Assert.Null(v.PageExecutionContext);
+                executed = true;
+            });
+
+            var view = new RazorView(Mock.Of<IRazorPageFactory>(),
+                                     Mock.Of<IRazorPageActivator>(),
+                                     Mock.Of<IViewStartProvider>());
+            view.Contextualize(page, isPartial, pageExecutionListener: null);
+            var viewContext = CreateViewContext(view);
+
+            // Act
+            await view.RenderAsync(viewContext);
+
+            // Assert
+            Assert.True(executed);
+        }
+
+        private static TextWriter CreateBufferedWriter()
+        {
+            var mockWriter = new Mock<TextWriter>();
+            var bufferedWriter = mockWriter.As<IBufferedTextWriter>();
+            bufferedWriter.SetupGet(b => b.IsBuffering)
+                          .Returns(true);
+            return mockWriter.Object;
+        }
+
         private static ViewContext CreateViewContext(RazorView view)
         {
             var httpContext = new DefaultHttpContext();
@@ -584,7 +734,7 @@ section-content-2";
         {
             viewStartPages = viewStartPages ?? new IRazorPage[0];
             var viewStartProvider = new Mock<IViewStartProvider>();
-            viewStartProvider.Setup(v => v.GetViewStartPages(It.IsAny<string>()))
+            viewStartProvider.Setup(v => v.GetViewStartPages(It.IsAny<string>(), false))
                              .Returns(viewStartPages);
 
             return viewStartProvider.Object;

test/WebSites/RazorInstrumentationWebsite/HomeController.cs

@@ -0,0 +1,21 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using Microsoft.AspNet.Mvc;
+
+namespace RazorInstrumentationWebSite
+{
+    public class HomeController : Controller
+    {
+        public ActionResult FullPath()
+        {
+            return View("/Views/Home/FullPath.cshtml");
+        }
+
+        public ActionResult ViewDiscoveryPath()
+        {
+            return View();
+        }
+    }
+}

test/WebSites/RazorInstrumentationWebsite/RazorInstrumentationWebsite.kproj

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="__ToolsVersion__" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <PropertyGroup>
+    <VisualStudioVersion Condition="'$(VisualStudioVersion)' == ''">14.0</VisualStudioVersion>
+    <VSToolsPath Condition="'$(VSToolsPath)' == ''">$(MSBuildExtensionsPath32)\Microsoft\VisualStudio\v$(VisualStudioVersion)</VSToolsPath>
+  </PropertyGroup>
+  <Import Project="$(VSToolsPath)\AspNet\Microsoft.Web.AspNet.Props" Condition="'$(VSToolsPath)' != ''" />
+  <PropertyGroup Label="Globals">
+    <ProjectGuid>2b2b9876-903c-4065-8d62-2ee832bba106</ProjectGuid>
+    <OutputType>Library</OutputType>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x86'" Label="Configuration">
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|x86'" Label="Configuration">
+  </PropertyGroup>
+  <PropertyGroup>
+    <SchemaVersion>2.0</SchemaVersion>
+  </PropertyGroup>
+  <Import Project="$(VSToolsPath)\AspNet\Microsoft.Web.AspNet.targets" Condition="'$(VSToolsPath)' != ''" />
+</Project>

test/WebSites/RazorInstrumentationWebsite/Startup.cs

@@ -0,0 +1,42 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Threading.Tasks;
+using Microsoft.AspNet.Builder;
+using Microsoft.AspNet.Http;
+using Microsoft.AspNet.PageExecutionInstrumentation;
+using Microsoft.Framework.DependencyInjection;
+
+namespace RazorInstrumentationWebSite
+{
+    public class Startup
+    {
+        public void Configure(IApplicationBuilder app)
+        {
+            var configuration = app.GetTestConfiguration();
+
+            // Set up application services
+            app.UseServices(services =>
+            {
+                // Add MVC services to the services container
+                services.AddMvc(configuration);
+            });
+
+            app.Use(async (HttpContext context, Func<Task> next) =>
+            {
+                if (!string.IsNullOrEmpty(context.Request.Headers["ENABLE-RAZOR-INSTRUMENTATION"]))
+                {
+                    var pageExecutionContext = context.ApplicationServices.GetService<TestPageExecutionContext>();
+                    var listenerFeature = new TestPageExecutionListenerFeature(pageExecutionContext);
+                    context.SetFeature<IPageExecutionListenerFeature>(listenerFeature);
+                }
+
+                await next();
+            });
+
+            // Add MVC to the request pipeline
+            app.UseMvc();
+        }
+    }
+}

test/WebSites/RazorInstrumentationWebsite/TestPageExecutionContext.cs

@@ -0,0 +1,24 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using Microsoft.AspNet.PageExecutionInstrumentation;
+
+namespace RazorInstrumentationWebSite
+{
+    public class TestPageExecutionContext : IPageExecutionContext
+    {
+        public List<Tuple<int, int, bool>> Values { get; }
+            = new List<Tuple<int, int, bool>>();
+
+        public void BeginContext(int position, int length, bool isLiteral)
+        {
+            Values.Add(Tuple.Create(position, length, isLiteral));
+        }
+
+        public void EndContext()
+        {
+        }
+    }
+}

test/WebSites/RazorInstrumentationWebsite/TestPageExecutionListenerFeature.cs

@@ -0,0 +1,28 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.IO;
+using Microsoft.AspNet.PageExecutionInstrumentation;
+
+namespace RazorInstrumentationWebSite
+{
+    public class TestPageExecutionListenerFeature : IPageExecutionListenerFeature
+    {
+        private readonly IPageExecutionContext _context;
+
+        public TestPageExecutionListenerFeature(IPageExecutionContext context)
+        {
+            _context = context; 
+        }
+
+        public TextWriter DecorateWriter(TextWriter writer)
+        {
+            return writer;
+        }
+
+        public IPageExecutionContext GetContext(string sourceFilePath, TextWriter writer)
+        {
+            return _context;
+        }
+    }
+}

test/WebSites/RazorInstrumentationWebsite/Views/Home/FullPath.cshtml

@@ -0,0 +1,3 @@
+<p class="@("Hello world")">
+page-content
+</p>

test/WebSites/RazorInstrumentationWebsite/Views/Home/ViewDiscoveryPath.cshtml

@@ -0,0 +1,3 @@
+<p class="@("Hello world")">
+page-content
+</p>

test/WebSites/RazorInstrumentationWebsite/Views/_Layout.cshtml

@@ -0,0 +1,4 @@
+<div>
+@int.MaxValue
+@RenderBody()
+</div>

test/WebSites/RazorInstrumentationWebsite/Views/_ViewStart.cshtml

@@ -0,0 +1,5 @@
+@{
+    Layout = "/Views/_Layout.cshtml";
+    var viewStartMessage = "viewstart-content";
+}
+@viewStartMessage

test/WebSites/RazorInstrumentationWebsite/project.json

@@ -0,0 +1,11 @@
+{
+    "dependencies": {
+        "Microsoft.AspNet.Mvc": "",
+        "Microsoft.AspNet.Server.IIS": "1.0.0-*",
+        "Microsoft.AspNet.Mvc.TestConfiguration": ""
+    },
+    "frameworks": {
+        "aspnet50": { },
+        "aspnetcore50": { }
+    }
+}