Fixes: #U4-1819

src/Umbraco.Tests/EnumerableExtensionsTests.cs

@@ -10,6 +10,77 @@ namespace Umbraco.Tests
 	[TestFixture]
     public class EnumerableExtensionsTests
     {
+
+	    [Test]
+	    public void Flatten_List()
+	    {
+	        var hierarchy = new TestItem()
+	            {
+	                Children = new List<TestItem>()
+	                    {
+	                        new TestItem()
+	                            {
+	                                Children = new List<TestItem>()
+	                                    {
+	                                        new TestItem()
+	                                            {
+	                                                Children = new List<TestItem>()
+	                                                    {
+	                                                        new TestItem()
+	                                                            {
+	                                                                Children = new List<TestItem>()
+	                                                                    {
+	                                                                        new TestItem(),
+                                                                            new TestItem()
+	                                                                    }
+	                                                            }
+	                                                    }
+	                                            }
+	                                    }
+	                            },
+	                        new TestItem()
+	                            {
+	                                Children = new List<TestItem>()
+	                                    {
+	                                        new TestItem()
+	                                            {
+	                                                Children = new List<TestItem>()
+	                                                    {
+	                                                        new TestItem()
+	                                                            {
+	                                                                Children = new List<TestItem>()
+	                                                            }
+	                                                    }
+	                                            },
+	                                        new TestItem()
+	                                            {
+	                                                Children = new List<TestItem>()
+	                                                    {
+	                                                        new TestItem()
+	                                                            {
+	                                                                Children = new List<TestItem>()
+	                                                            }
+	                                                    }
+	                                            }
+	                                    }
+	                            },
+	                    }
+	            };
+
+	        var flattened = hierarchy.Children.FlattenList(x => x.Children);
+
+            Assert.AreEqual(10, flattened.Count());
+	    }
+
+        private class TestItem
+        {
+            public TestItem()
+            {
+                Children = Enumerable.Empty<TestItem>();
+            }
+            public IEnumerable<TestItem> Children { get; set; } 
+        }
+
         [Test]
         public void InGroupsOf_ReturnsAllElements()
         {

src/Umbraco.Web/Mvc/NotChildAction.cs

@@ -0,0 +1,20 @@
+using System.Web.Mvc;
+
+namespace Umbraco.Web.Mvc
+{
+    /// <summary>
+    /// Used to ensure that actions with duplicate names that are not child actions don't get executed when 
+    /// we are Posting and not redirecting.
+    /// </summary>
+    /// <remarks>
+    /// See issue: http://issues.umbraco.org/issue/U4-1819
+    /// </remarks>
+    public class NotChildAction : ActionMethodSelectorAttribute
+    {
+        public override bool IsValidForRequest(ControllerContext controllerContext, System.Reflection.MethodInfo methodInfo)
+        {
+            var isChildAction = controllerContext.IsChildAction;
+            return !isChildAction;
+        }
+    }
+}

src/Umbraco.Web/Umbraco.Web.csproj

@@ -273,6 +273,7 @@
     <Compile Include="DefaultPublishedMediaStore.cs" />
     <Compile Include="Dictionary\UmbracoCultureDictionary.cs" />
     <Compile Include="Dictionary\UmbracoCultureDictionaryFactory.cs" />
+    <Compile Include="Mvc\NotChildAction.cs" />
     <Compile Include="Mvc\UmbracoViewPage.cs" />
     <Compile Include="PublishedContentExtensions.cs" />
     <Compile Include="ExamineExtensions.cs" />