Restore the TextWriter to ViewContext

src/Microsoft.AspNet.Mvc.Core/ActionResults/ViewResult.cs

@@ -36,7 +36,9 @@ namespace Microsoft.AspNet.Mvc
                     var viewContext = new ViewContext(_serviceProvider, context.HttpContext, context.RouteValues, ViewData)
                     {
                         Url = new UrlHelper(context.HttpContext, context.Router, context.RouteValues),
+                        Writer = writer,
                     };
+
                     await view.RenderAsync(viewContext, writer);
                 }
             }

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

@@ -31,7 +31,20 @@ namespace Microsoft.AspNet.Mvc.Razor
             using (var bodyWriter = new StringWriter(contentBuilder))
             {
                 Output = bodyWriter;
-                await ExecuteAsync();
+
+                // 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 = bodyWriter;
+
+                try
+                {
+                    await ExecuteAsync();
+                }
+                finally
+                {
+                    context.Writer = oldWriter;
+                }
             }
 
             var bodyContent = contentBuilder.ToString();

src/Microsoft.AspNet.Mvc.Rendering/View/ViewContext.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.IO;
 using Microsoft.AspNet.Abstractions;
 
 namespace Microsoft.AspNet.Mvc.Rendering
@@ -23,5 +24,7 @@ namespace Microsoft.AspNet.Mvc.Rendering
         public ViewData ViewData { get; private set; }
 
         public IDictionary<string, object> ViewEngineContext { get; private set; }
+
+        public TextWriter Writer { get; set; }
     }
 }