RadioButtonFor doesnt resolve isChecked properly when nested

src/System.Web.Mvc/Html/InputExtensions.cs

@@ -358,7 +358,7 @@ private static MvcHtmlString RadioButtonHelper(HtmlHelper htmlHelper, ModelMetad
             {
                 string valueString = Convert.ToString(value, CultureInfo.CurrentCulture);
                 isChecked = model != null &&
-                            !String.IsNullOrEmpty(name) &&
+                            !String.IsNullOrEmpty(htmlHelper.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(name)) &&
                             String.Equals(model.ToString(), valueString, StringComparison.OrdinalIgnoreCase);
             }
 

test/System.Web.Mvc.Test/Html/Test/InputExtensionsTest.cs

@@ -3,6 +3,7 @@
 
 using System.ComponentModel.DataAnnotations;
 using System.Data.Linq;
+using System.Linq.Expressions;
 using System.Web.Mvc.Test;
 using System.Web.Routing;
 using System.Web.WebPages.Scope;
@@ -2147,6 +2148,19 @@ public void RadioButtonForWithNameAndValue()
             Assert.Equal(@"<input checked=""checked"" id=""foo"" name=""foo"" type=""radio"" value=""ViewDataFoo"" />", html.ToHtmlString());
         }
 
+        [Fact]
+        public void RadioButtonForWithNestedNameAndValue()
+        {
+            // Arrange
+            HtmlHelper<string> helper = MvcHelper.GetHtmlHelper(GetRadioButtonNestedAndUnsetViewData());
+
+            // Act
+            MvcHtmlString html = helper.RadioButtonFor(m => m, "ViewItemFoo");
+
+            // Assert
+            Assert.Equal(@"<input checked=""checked"" id=""foo"" name=""foo"" type=""radio"" value=""ViewItemFoo"" />", html.ToHtmlString());
+        }
+
         [Fact]
         public void RadioButtonForWithNameAndValue_Unobtrusive()
         {
@@ -3056,6 +3070,31 @@ private static ViewDataDictionary<FooBarModel> GetRadioButtonViewData()
             return viewData;
         }
 
+        private static ViewDataDictionary<string> GetRadioButtonNestedAndUnsetViewData()
+        {
+            ViewDataDictionary<FooBarModel> viewData = new ViewDataDictionary<FooBarModel> { };
+            viewData.Model = new FooBarModel { foo = "ViewItemFoo", bar = "ViewItemBar" };
+
+
+            Expression<Func<FooBarModel, string>> containedExpression = m => m.foo;
+
+            var metadata = ModelMetadata.FromLambdaExpression(containedExpression, viewData);
+            var htmlFieldName = ExpressionHelper.GetExpressionText(containedExpression);
+
+
+            ViewDataDictionary nestedViewData = new ViewDataDictionary(viewData)
+            {
+                Model = metadata.Model,
+                ModelMetadata = metadata,
+                TemplateInfo = new TemplateInfo
+                {
+                    HtmlFieldPrefix = viewData.TemplateInfo.GetFullHtmlFieldName(htmlFieldName),
+                }
+            };
+
+            return new ViewDataDictionary<string>(nestedViewData);
+        }
+
         // TEXTBOX
         private static readonly RouteValueDictionary _attributesDictionary = new RouteValueDictionary(new { baz = "BazValue" });
         private static readonly object _attributesObjectDictionary = new { baz = "BazObjValue" };