AppDomain safety

src/Microsoft.AspNetCore.Mvc.Core/Infrastructure/ActionContextAccessor.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 #if NET451
+using System;
 using System.Runtime.Remoting;
 using System.Runtime.Remoting.Messaging;
 #else
@@ -13,7 +14,7 @@ namespace Microsoft.AspNetCore.Mvc.Infrastructure
     public class ActionContextAccessor : IActionContextAccessor
     {
 #if NET451
-        private static string Key = typeof(ActionContext).FullName;
+        private static readonly string Key = typeof(ActionContext).FullName + AppDomain.CurrentDomain.Id;
 
         public ActionContext ActionContext
         {

test/Microsoft.AspNetCore.Mvc.Core.Test/Infrastructure/ActionContextAccessorTests.cs

@@ -0,0 +1,37 @@
+// 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;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Mvc.Infrastructure
+{
+#if NET451
+    public class ActionContextAccessorTests
+    {
+        private static void DomainFunc()
+        {
+            var accessor = new ActionContextAccessor();
+            Assert.Equal(null, accessor.ActionContext);
+            accessor.ActionContext = new ActionContext();
+        }
+
+        [Fact]
+        public void ChangingAppDomainsDoesNotBreak_ActionContextAccessor()
+        {
+            // Arrange
+            var accessor = new ActionContextAccessor();
+            var context = new ActionContext();
+            var domain = AppDomain.CreateDomain("newDomain");
+
+            // Act
+            domain.DoCallBack(DomainFunc);
+            AppDomain.Unload(domain);
+            accessor.ActionContext = context;
+
+            // Assert
+            Assert.True(ReferenceEquals(context, accessor.ActionContext));
+        }
+    }
+#endif
+}