RazorView should not create new ViewContext when rendering pages.

For pages that can pop back (e.g. Partial pages \ View Components), the
invoking component already creates a new ViewContext. ViewStart, Pages
and Layouts need to share the same Layout. This is required for sharing
ViewData values (such as title).

Fixes #861

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

@@ -88,12 +88,8 @@ namespace Microsoft.AspNet.Mvc.Razor
 
         private async Task RenderPageCoreAsync(IRazorPage page, ViewContext context)
         {
-            // Activating a page might mutate the ViewContext (for instance ViewContext.ViewData) is mutated by 
-            // RazorPageActivator. We'll instead pass in a copy of the ViewContext.
-            var pageViewContext = new ViewContext(context, context.View, context.ViewData, context.Writer);
-            page.ViewContext = pageViewContext;
-            _pageActivator.Activate(page, pageViewContext);
-
+            page.ViewContext = context;
+            _pageActivator.Activate(page, context);
             await page.ExecuteAsync();
         }
 

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

@@ -85,5 +85,24 @@ test-value";
             var body = await result.HttpContext.Response.ReadBodyAsStringAsync();
             Assert.Equal(expected, body.Trim());
         }
+
+        [Fact]
+        public async Task RazorView_PassesViewContextBetweenViewAndLayout()
+        {
+            var expected =
+@"<title>Page title</title>
+
+partial-content
+component-content";
+            var server = TestServer.Create(_provider, _app);
+            var client = server.Handler;
+
+            // Act
+            var result = await client.GetAsync("http://localhost/ViewEngine/ViewPassesViewDataToLayout");
+
+            // Assert
+            var body = await result.HttpContext.Response.ReadBodyAsStringAsync();
+            Assert.Equal(expected, body.Trim());
+        }
     }
 }

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

@@ -42,7 +42,7 @@ namespace Microsoft.AspNet.Mvc.Razor
         }
 
         [Fact]
-        public async Task RenderAsync_WithoutHierarchy_ActivatesViews_WithACopyOfViewContext()
+        public async Task RenderAsync_WithoutHierarchy_ActivatesViews_WithThePassedInViewContext()
         {
             // Arrange
             var viewData = new ViewDataDictionary(Mock.Of<IModelMetadataProvider>());
@@ -59,12 +59,11 @@ namespace Microsoft.AspNet.Mvc.Razor
                                      page,
                                      executeViewHierarchy: false);
             var viewContext = CreateViewContext(view);
-            var expectedViewData = viewContext.ViewData;
             var expectedWriter = viewContext.Writer;
             activator.Setup(a => a.Activate(page, It.IsAny<ViewContext>()))
                      .Callback((IRazorPage p, ViewContext c) =>
                      {
-                         Assert.NotSame(c, viewContext);
+                         Assert.Same(c, viewContext);
                          c.ViewData = viewData;
                      })
                      .Verifiable();
@@ -74,7 +73,6 @@ namespace Microsoft.AspNet.Mvc.Razor
 
             // Assert
             activator.Verify();
-            Assert.Same(expectedViewData, viewContext.ViewData);
             Assert.Same(expectedWriter, viewContext.Writer);
         }
 

test/WebSites/RazorWebSite/Components/ComponentThatSetsTitle.cs

@@ -0,0 +1,16 @@
+// 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 Microsoft.AspNet.Mvc;
+
+namespace MvcSample.Web.Components
+{
+    [ViewComponent(Name = "ComponentThatSetsTitle")]
+    public class ComponentThatSetsTitle : ViewComponent
+    {
+        public IViewComponentResult Invoke()
+        {
+            return View();
+        }
+    }
+}

test/WebSites/RazorWebSite/Controllers/ViewEngineController.cs

@@ -36,5 +36,11 @@ namespace RazorWebSite.Controllers
             };
             return View(model);
         }
+
+        public ViewResult ViewPassesViewDataToLayout()
+        {
+            ViewData["Title"] = "Controller title";
+            return View("ViewWithTitle");
+        }
     }
 }

test/WebSites/RazorWebSite/RazorWebSite.kproj

@@ -24,7 +24,11 @@
   </PropertyGroup>
   <ItemGroup>
     <Content Include="Project.json" />
+    <Content Include="Views\Shared\Components\ComponentThatSetsTitle\Default.cshtml" />
+    <Content Include="Views\Shared\_LayoutWithTitle.cshtml" />
     <Content Include="Views\Shared\_Partial.cshtml" />
+    <Content Include="Views\Shared\_PartialThatSetsTitle.cshtml" />
+    <Content Include="Views\ViewEngine\ViewWithTitle.cshtml" />
     <Content Include="Views\ViewEngine\ViewWithNestedLayout.cshtml" />
     <Content Include="Views\ViewEngine\ViewWithLayout.cshtml" />
     <Content Include="Views\ViewEngine\ViewWithFullPath.cshtml" />
@@ -34,6 +38,7 @@
     <Content Include="Views\ViewEngine\_NestedLayout.cshtml" />
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="Components\ComponentThatSetsTitle.cs" />
     <Compile Include="Controllers\ViewEngineController.cs" />
     <Compile Include="Models\Person.cs" />
     <Compile Include="Models\Address.cs" />

test/WebSites/RazorWebSite/Views/Shared/Components/ComponentThatSetsTitle/Default.cshtml

@@ -0,0 +1,4 @@
+@{ 
+    ViewData["Title"] = "Component title";
+}
+component-content

test/WebSites/RazorWebSite/Views/Shared/_LayoutWithTitle.cshtml

@@ -0,0 +1,2 @@
+<title>@ViewBag.Title</title>
+@RenderBody()

test/WebSites/RazorWebSite/Views/Shared/_PartialThatSetsTitle.cshtml

@@ -0,0 +1,4 @@
+@{ 
+    ViewBag.Title = "Partial title";
+}
+partial-content

test/WebSites/RazorWebSite/Views/ViewEngine/ViewWithTitle.cshtml

@@ -0,0 +1,7 @@
+@{
+    ViewData["Title"] = "Page title";
+    // The invoked partial sets a title, but this shouldn't override the current page's ViewData \ ViewBag.
+    await Html.RenderPartialAsync("_PartialThatSetsTitle");
+    await Component.RenderInvokeAsync("ComponentThatSetsTitle");
+    Layout = "/Views/Shared/_LayoutWithTitle.cshtml";
+}