Imported Upstream version 3.6.0

Former-commit-id: da6be194a6b1221998fc28233f2503bd61dd9d14

external/aspnetwebstack/src/System.Web.Mvc/ViewStartPage.cs

@@ -0,0 +1,45 @@
+// Copyright (c) Microsoft Corporation. All rights reserved. See License.txt in the project root for license information.
+
+using System.Web.Mvc.Properties;
+using System.Web.WebPages;
+
+namespace System.Web.Mvc
+{
+    public abstract class ViewStartPage : StartPage, IViewStartPageChild
+    {
+        private IViewStartPageChild _viewStartPageChild;
+
+        public HtmlHelper<object> Html
+        {
+            get { return ViewStartPageChild.Html; }
+        }
+
+        public UrlHelper Url
+        {
+            get { return ViewStartPageChild.Url; }
+        }
+
+        public ViewContext ViewContext
+        {
+            get { return ViewStartPageChild.ViewContext; }
+        }
+
+        internal IViewStartPageChild ViewStartPageChild
+        {
+            get
+            {
+                if (_viewStartPageChild == null)
+                {
+                    IViewStartPageChild child = ChildPage as IViewStartPageChild;
+                    if (child == null)
+                    {
+                        throw new InvalidOperationException(MvcResources.ViewStartPage_RequiresMvcRazorView);
+                    }
+                    _viewStartPageChild = child;
+                }
+
+                return _viewStartPageChild;
+            }
+        }
+    }
+}