Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Web.ApplicationServices/Util/SystemWebProxy.cs

@@ -0,0 +1,52 @@
+//------------------------------------------------------------------------------
+// <copyright file="SystemWebProxy.cs" company="Microsoft">
+//    Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>
+//------------------------------------------------------------------------------
+
+namespace System.Web.Util {
+    using System;
+    using System.Collections.Generic;
+    using System.Diagnostics;
+    using System.Reflection;
+    using System.Web.Security;
+    using System.Security.Permissions;    
+
+    // Because this assembly ships in the client SKU, whereas System.Web.dll ships in the Extended SKU, we need to
+    // proxy any usage of System.Web.dll. This allows us to fail gracefully if the Extended SKU is not present. 
+    // Users can avoid this failure by overridding all virtual members on both of these types which will prevent 
+    // this class, and hence, System.Web.dll, from ever being called.
+    internal static class SystemWebProxy {
+
+        public static readonly IMembershipAdapter Membership = GetMembershipAdapter();
+
+        private static IMembershipAdapter GetMembershipAdapter() {
+            IMembershipAdapter membership = CreateSystemWebMembershipAdapter();
+            if (membership == null) {
+                membership = new DefaultMembershipAdapter();
+            }
+
+            return membership;
+        }
+
+        private static IMembershipAdapter CreateSystemWebMembershipAdapter() {
+            Type type = Type.GetType("System.Web.Security.MembershipAdapter, " + AssemblyRef.SystemWeb, throwOnError:false);
+            if (type != null) {
+                // Running on Extended SKU
+
+                return (IMembershipAdapter)DangerousCreateInstance(type);
+            }
+
+            // Running on Client SKU
+            return null;            
+        }
+
+        // Partially trusted callers might not have permissions to create an instance of 
+        // System.Web’s MembershipAdapter type (it’s an internal type), so give them access.
+        [ReflectionPermission(SecurityAction.Assert, Flags=ReflectionPermissionFlag.MemberAccess)]
+        private static object DangerousCreateInstance(Type type) {
+
+            return Activator.CreateInstance(type);
+        }
+    }
+}