Add DiagnosticSource to RazorView (#6386)

Addresses #6222

src/Microsoft.AspNetCore.Mvc.Razor/Internal/MvcRazorDiagnosticSourceExtensions.cs

@@ -0,0 +1,49 @@
+// 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.Diagnostics;
+using Microsoft.AspNetCore.Mvc.Rendering;
+
+namespace Microsoft.AspNetCore.Mvc.Razor.Internal
+{
+    public static class MvcRazorDiagnosticSourceExtensions
+    {
+        public static void BeforeViewPage(
+            this DiagnosticSource diagnosticSource,
+            IRazorPage page,
+            ViewContext viewContext)
+        {
+            if (diagnosticSource.IsEnabled("Microsoft.AspNetCore.Mvc.Razor.BeforeViewPage"))
+            {
+                diagnosticSource.Write(
+                    "Microsoft.AspNetCore.Mvc.Razor.BeforeViewPage",
+                    new
+                    {
+                        page = page,
+                        viewContext = viewContext,
+                        actionDescriptor = viewContext.ActionDescriptor,
+                        httpContext = viewContext.HttpContext,
+                    });
+            }
+        }
+
+        public static void AfterViewPage(
+            this DiagnosticSource diagnosticSource,
+            IRazorPage page,
+            ViewContext viewContext)
+        {
+            if (diagnosticSource.IsEnabled("Microsoft.AspNetCore.Mvc.Razor.AfterViewPage"))
+            {
+                diagnosticSource.Write(
+                    "Microsoft.AspNetCore.Mvc.Razor.AfterViewPage",
+                    new
+                    {
+                        page = page,
+                        viewContext = viewContext,
+                        actionDescriptor = viewContext.ActionDescriptor,
+                        httpContext = viewContext.HttpContext,
+                    });
+            }
+        }
+    }
+}

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

@@ -10,6 +10,7 @@ using System.Threading.Tasks;
 using Microsoft.AspNetCore.Mvc.Rendering;
 using Microsoft.AspNetCore.Mvc.ViewEngines;
 using Microsoft.AspNetCore.Mvc.ViewFeatures.Internal;
+using Microsoft.AspNetCore.Mvc.Razor.Internal;
 using Microsoft.Extensions.DependencyInjection;
 
 namespace Microsoft.AspNetCore.Mvc.Razor
@@ -23,6 +24,7 @@ namespace Microsoft.AspNetCore.Mvc.Razor
         private readonly IRazorViewEngine _viewEngine;
         private readonly IRazorPageActivator _pageActivator;
         private readonly HtmlEncoder _htmlEncoder;
+        private readonly DiagnosticSource _diagnosticSource;
         private IViewBufferScope _bufferScope;
 
         /// <summary>
@@ -34,12 +36,14 @@ namespace Microsoft.AspNetCore.Mvc.Razor
         /// </param>
         /// <param name="razorPage">The <see cref="IRazorPage"/> instance to execute.</param>
         /// <param name="htmlEncoder">The HTML encoder.</param>
+        /// <param name="diagnosticSource">The <see cref="DiagnosticSource"/>.</param>
         public RazorView(
             IRazorViewEngine viewEngine,
             IRazorPageActivator pageActivator,
             IReadOnlyList<IRazorPage> viewStartPages,
             IRazorPage razorPage,
-            HtmlEncoder htmlEncoder)
+            HtmlEncoder htmlEncoder,
+            DiagnosticSource diagnosticSource)
         {
             if (viewEngine == null)
             {
@@ -66,11 +70,17 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 throw new ArgumentNullException(nameof(htmlEncoder));
             }
 
+            if (diagnosticSource == null)
+            {
+                throw new ArgumentNullException(nameof(diagnosticSource));
+            }
+
             _viewEngine = viewEngine;
             _pageActivator = pageActivator;
             ViewStartPages = viewStartPages;
             RazorPage = razorPage;
             _htmlEncoder = htmlEncoder;
+            _diagnosticSource = diagnosticSource;
         }
 
         /// <inheritdoc />
@@ -152,11 +162,21 @@ namespace Microsoft.AspNetCore.Mvc.Razor
             }
         }
 
-        private Task RenderPageCoreAsync(IRazorPage page, ViewContext context)
+        private async Task RenderPageCoreAsync(IRazorPage page, ViewContext context)
         {
             page.ViewContext = context;
             _pageActivator.Activate(page, context);
-            return page.ExecuteAsync();
+
+            _diagnosticSource.BeforeViewPage(page, context);
+
+            try
+            {
+                await page.ExecuteAsync();
+            }
+            finally
+            {
+                _diagnosticSource.AfterViewPage(page, context);
+            }
         }
 
         private async Task RenderViewStartsAsync(ViewContext context)

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

@@ -44,6 +44,7 @@ namespace Microsoft.AspNetCore.Mvc.Razor
         private readonly ILogger _logger;
         private readonly RazorViewEngineOptions _options;
         private readonly RazorProject _razorProject;
+        private readonly DiagnosticSource _diagnosticSource;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="RazorViewEngine" />.
@@ -54,7 +55,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
             HtmlEncoder htmlEncoder,
             IOptions<RazorViewEngineOptions> optionsAccessor,
             RazorProject razorProject,
-            ILoggerFactory loggerFactory)
+            ILoggerFactory loggerFactory,
+            DiagnosticSource diagnosticSource)
         {
             _options = optionsAccessor.Value;
 
@@ -77,6 +79,7 @@ namespace Microsoft.AspNetCore.Mvc.Razor
             _htmlEncoder = htmlEncoder;
             _logger = loggerFactory.CreateLogger<RazorViewEngine>();
             _razorProject = razorProject;
+            _diagnosticSource = diagnosticSource;
             ViewLookupCache = new MemoryCache(new MemoryCacheOptions());
         }
 
@@ -466,7 +469,7 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 viewStarts[i] = viewStartItem.PageFactory();
             }
 
-            var view = new RazorView(this, _pageActivator, viewStarts, page, _htmlEncoder);
+            var view = new RazorView(this, _pageActivator, viewStarts, page, _htmlEncoder, _diagnosticSource);
             return ViewEngineResult.Found(viewName, view);
         }
 

src/Microsoft.AspNetCore.Mvc.RazorPages/Infrastructure/PageResultExecutor.cs

@@ -19,6 +19,7 @@ namespace Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure
     {
         private readonly IRazorViewEngine _razorViewEngine;
         private readonly IRazorPageActivator _razorPageActivator;
+        private readonly DiagnosticSource _diagnosticSource;
         private readonly HtmlEncoder _htmlEncoder;
 
         /// <summary>
@@ -42,6 +43,7 @@ namespace Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure
             _razorViewEngine = razorViewEngine;
             _htmlEncoder = htmlEncoder;
             _razorPageActivator = razorPageActivator;
+            _diagnosticSource = diagnosticSource;
         }
 
         /// <summary>
@@ -76,7 +78,8 @@ namespace Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure
                 _razorPageActivator,
                 viewStarts,
                 new RazorPageAdapter(result.Page),
-                _htmlEncoder);
+                _htmlEncoder,
+                _diagnosticSource);
 
             return ExecuteAsync(viewContext, result.ContentType, result.StatusCode);
         }

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

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Threading;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
@@ -1350,7 +1351,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Test
                 new HtmlTestEncoder(),
                 GetOptionsAccessor(expanders: null),
                 new FileProviderRazorProject(new TestFileProvider()),
-                loggerFactory);
+                loggerFactory,
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
 
             // Act
             var result = viewEngine.CreateCacheResult(null, relativePath, false);
@@ -1881,7 +1883,7 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Test
                 IRazorPageFactoryProvider pageFactory,
                 IOptions<RazorViewEngineOptions> optionsAccessor,
                 RazorProject razorProject)
-                : base(pageFactory, Mock.Of<IRazorPageActivator>(), new HtmlTestEncoder(), optionsAccessor, razorProject, NullLoggerFactory.Instance)
+                : base(pageFactory, Mock.Of<IRazorPageActivator>(), new HtmlTestEncoder(), optionsAccessor, razorProject, NullLoggerFactory.Instance, new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"))
             {
             }
 

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

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.IO;
 using System.Linq;
 using System.Threading.Tasks;
@@ -45,7 +46,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new IRazorPage[0],
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
             var expected = viewContext.Writer;
 
@@ -74,7 +76,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 activator.Object,
                 new IRazorPage[0],
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
 
             var viewContext = CreateViewContext(view);
             var expectedWriter = viewContext.Writer;
@@ -95,6 +98,55 @@ namespace Microsoft.AspNetCore.Mvc.Razor
             Assert.Same(expectedWriter, viewContext.Writer);
         }
 
+        [Fact]
+        public async Task RenderAsync_AsPartial_ActivatesViews_WritesBeforeAndAfterRazorViewEventDiagnostics()
+        {
+            // Arrange
+            var viewData = new ViewDataDictionary(new EmptyModelMetadataProvider(), new ModelStateDictionary());
+            var page = new TestableRazorPageForDiagnostics(v =>
+            {
+                // viewData is assigned to ViewContext by the activator
+                Assert.Same(viewData, v.ViewContext.ViewData);
+            });
+            var activator = new Mock<IRazorPageActivator>();
+
+            var adapter = new TestDiagnosticListener();
+            var diagnosticSource = new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor");
+            diagnosticSource.SubscribeWithAdapter(adapter);
+
+            var view = new RazorView(
+                Mock.Of<IRazorViewEngine>(),
+                activator.Object,
+                new IRazorPage[0],
+                page,
+                new HtmlTestEncoder(),
+                diagnosticSource);
+
+            var viewContext = CreateViewContext(view);
+            var expectedWriter = viewContext.Writer;
+            activator
+                .Setup(a => a.Activate(page, It.IsAny<ViewContext>()))
+                .Callback((IRazorPage p, ViewContext c) =>
+                {
+                    Assert.Same(c, viewContext);
+                    c.ViewData = viewData;
+                })
+                .Verifiable();
+
+            // Act
+            await view.RenderAsync(viewContext);
+
+            // Assert
+            Assert.NotNull(adapter.BeforeViewPage?.Page);
+            Assert.NotNull(adapter.BeforeViewPage?.ViewContext);
+            Assert.NotNull(adapter.BeforeViewPage?.ActionDescriptor);
+            Assert.NotNull(adapter.BeforeViewPage?.HttpContext);
+            Assert.NotNull(adapter.AfterViewPage?.Page);
+            Assert.NotNull(adapter.AfterViewPage?.ViewContext);
+            Assert.NotNull(adapter.AfterViewPage?.ActionDescriptor);
+            Assert.NotNull(adapter.AfterViewPage?.HttpContext);
+        }
+
         [Fact]
         public async Task ViewContext_ExecutingPagePath_ReturnsPathOfRazorPageBeingExecuted()
         {
@@ -143,7 +195,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 activator,
                 new[] { viewStart },
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
 
             var viewContext = CreateViewContext(view);
             var expectedWriter = viewContext.Writer;
@@ -169,7 +222,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 activator.Object,
                 new IRazorPage[0],
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
 
             // Act
@@ -216,7 +270,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new IRazorPage[0],
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
 
             // Act
@@ -240,7 +295,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new IRazorPage[0],
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
             var original = viewContext.Writer;
 
@@ -265,7 +321,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new IRazorPage[0],
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
             var original = viewContext.Writer;
 
@@ -293,7 +350,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 activator.Object,
                 new IRazorPage[0],
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
 
             // Act
@@ -348,7 +406,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 activator.Object,
                 new[] { viewStart1, viewStart2 },
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
 
             // Act
@@ -391,7 +450,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new IRazorPage[0],
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var context = CreateViewContext(view);
 
             // Act
@@ -444,7 +504,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new[] { viewStart },
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var context = CreateViewContext(view);
 
             // Act
@@ -477,7 +538,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new IRazorPage[0],
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
             viewEngine
                 .Setup(v => v.GetPage(/*executingFilePath*/ null, layoutPath))
@@ -519,7 +581,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new IRazorPage[0],
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
             viewEngine
                 .Setup(v => v.GetPage(/*executingFilePath*/ null, layoutPath))
@@ -563,7 +626,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new IRazorPage[0],
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
             viewEngine
                 .Setup(v => v.GetPage(/*executingFilePath*/ null, layoutPath))
@@ -638,7 +702,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 activator.Object,
                 new IRazorPage[0],
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
 
             // Act
@@ -678,7 +743,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new IRazorPage[0],
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
 
             // Act and Assert
@@ -744,7 +810,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new IRazorPage[0],
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
 
             // Act
@@ -812,7 +879,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new IRazorPage[0],
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
 
             // Act
@@ -874,7 +942,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new IRazorPage[0],
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
 
             // Act and Assert
@@ -942,7 +1011,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new IRazorPage[0],
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
 
             // Act and Assert
@@ -976,7 +1046,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new IRazorPage[0],
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
 
             // Act and Assert
@@ -1043,7 +1114,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new IRazorPage[0],
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
 
             // Act
@@ -1116,7 +1188,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new IRazorPage[0],
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
 
             // Act
@@ -1156,7 +1229,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new IRazorPage[0],
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
 
             // Act and Assert
@@ -1209,7 +1283,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new IRazorPage[0],
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
 
             // Act and Assert
@@ -1278,7 +1353,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new IRazorPage[0],
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
 
             // Act
@@ -1335,7 +1411,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new IRazorPage[0],
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
 
             // Act
@@ -1389,7 +1466,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new IRazorPage[0],
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
 
             // Act
@@ -1419,7 +1497,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new IRazorPage[0],
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
 
             // Act and Assert
@@ -1465,7 +1544,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new IRazorPage[0],
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
 
             // Act and Assert
@@ -1509,7 +1589,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new[] { viewStart1, viewStart2 },
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
 
             // Act
@@ -1566,7 +1647,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new[] { viewStart1, viewStart2 },
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
 
             // Act
@@ -1610,7 +1692,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new[] { viewStart1, viewStart2 },
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
 
             // Act
@@ -1651,7 +1734,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 Mock.Of<IRazorPageActivator>(),
                 new[] { viewStart1, viewStart2 },
                 page,
-                new HtmlTestEncoder());
+                new HtmlTestEncoder(),
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
             var viewContext = CreateViewContext(view);
 
             // Act
@@ -1678,6 +1762,28 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 new HtmlHelperOptions());
         }
 
+        public class TestableRazorPageForDiagnostics : RazorPage
+        {
+            private readonly Action<TestableRazorPageForDiagnostics> _executeAction;
+
+            public TestableRazorPageForDiagnostics(Action<TestableRazorPageForDiagnostics> executeAction)
+            {
+                _executeAction = executeAction;
+                HtmlEncoder = new HtmlTestEncoder();
+            }
+
+            public void RenderBodyPublic()
+            {
+                Write(RenderBody());
+            }
+
+            public override Task ExecuteAsync()
+            {
+                _executeAction(this);
+                return Task.FromResult(0);
+            }
+        }
+
         private class TestableRazorPage : RazorPage
         {
             private readonly Action<TestableRazorPage> _executeAction;

test/Microsoft.AspNetCore.Mvc.TestDiagnosticListener/IProxyPage.cs

@@ -0,0 +1,9 @@
+// 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.
+
+namespace Microsoft.AspNetCore.Mvc
+{
+    public interface IProxyPage
+    {
+    }
+}

test/Microsoft.AspNetCore.Mvc.TestDiagnosticListener/TestDiagnosticListener.cs

@@ -221,6 +221,58 @@ namespace Microsoft.AspNetCore.Mvc
             };
         }
 
+        public class OnBeforeViewPageEventData
+        {
+            public IProxyPage Page { get; set; }
+            public IProxyViewContext ViewContext { get; set; }
+            public IProxyActionDescriptor ActionDescriptor { get; set; }
+            public IProxyHttpContext HttpContext { get; set; }
+        }
+
+        public OnBeforeViewPageEventData BeforeViewPage { get; set; }
+
+        [DiagnosticName("Microsoft.AspNetCore.Mvc.Razor.BeforeViewPage")]
+        public virtual void OnBeforeViewPage(
+            IProxyPage page,
+            IProxyViewContext viewContext,
+            IProxyActionDescriptor actionDescriptor,
+            IProxyHttpContext httpContext)
+        {
+            BeforeViewPage = new OnBeforeViewPageEventData()
+            {
+                Page = page,
+                ViewContext = viewContext,
+                ActionDescriptor = actionDescriptor,
+                HttpContext = httpContext,
+            };
+        }
+
+        public class OnAfterViewPageEventData
+        {
+            public IProxyPage Page { get; set; }
+            public IProxyViewContext ViewContext { get; set; }
+            public IProxyActionDescriptor ActionDescriptor { get; set; }
+            public IProxyHttpContext HttpContext { get; set; }
+        }
+
+        public OnAfterViewPageEventData AfterViewPage { get; set; }
+
+        [DiagnosticName("Microsoft.AspNetCore.Mvc.Razor.AfterViewPage")]
+        public virtual void OnAfterViewPage(
+            IProxyPage page,
+            IProxyViewContext viewContext,
+            IProxyActionDescriptor actionDescriptor,
+            IProxyHttpContext httpContext)
+        {
+            AfterViewPage = new OnAfterViewPageEventData()
+            {
+                Page = page,
+                ViewContext = viewContext,
+                ActionDescriptor = actionDescriptor,
+                HttpContext = httpContext,
+            };
+        }
+
         public class OnBeforeViewComponentEventData
         {
             public IProxyActionDescriptor ActionDescriptor { get; set; }