Update SelectExtensions to handle nested expressions where no name is parsed

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

@@ -285,7 +285,7 @@ private static MvcHtmlString ListBoxHelper(HtmlHelper htmlHelper, ModelMetadata
         private static IEnumerable<SelectListItem> GetSelectData(this HtmlHelper htmlHelper, string name)
         {
             object o = null;
-            if (htmlHelper.ViewData != null)
+            if (htmlHelper.ViewData != null && !String.IsNullOrEmpty(name))
             {
                 o = htmlHelper.ViewData.Eval(name);
             }
@@ -396,9 +396,9 @@ private static MvcHtmlString SelectInternal(this HtmlHelper htmlHelper, ModelMet
 
             // If we haven't already used ViewData to get the entire list of items then we need to
             // use the ViewData-supplied value before using the parameter-supplied value.
-            if (defaultValue == null && !String.IsNullOrEmpty(name))
+            if (defaultValue == null)
             {
-                if (!usedViewData)
+                if (!usedViewData && !String.IsNullOrEmpty(name))
                 {
                     defaultValue = htmlHelper.ViewData.Eval(name);
                 }

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

@@ -19,6 +19,7 @@ public class SelectExtensionsTest : IDisposable
     {
         private static readonly ViewDataDictionary<FooModel> _listBoxViewData = new ViewDataDictionary<FooModel> { { "foo", new[] { "Bravo" } } };
         private static readonly ViewDataDictionary<FooModel> _dropDownListViewData = new ViewDataDictionary<FooModel> { { "foo", "Bravo" } };
+        private static readonly ViewDataDictionary<FooContainerModel> _nestedDropDownListViewData = new ViewDataDictionary<FooContainerModel> { { "foo", "Bravo" } };
         private static readonly ViewDataDictionary<NonIEnumerableModel> _nonIEnumerableViewData = new ViewDataDictionary<NonIEnumerableModel> { { "foo", 1 } };
         private static readonly ViewDataDictionary<EnumModel> _enumDropDownListViewData = new ViewDataDictionary<EnumModel>
         {
@@ -1191,6 +1192,48 @@ public void DropDownListForUsesLambdaDefaultValue()
               + "</select>",
                 html.ToHtmlString());
         }
+
+        [Fact]
+        public void DropDownListForUsesLambdaDefaultValueWhenNested()
+        {
+            // Arrange
+            FooModel model = new FooModel { foo = "Bravo" };
+            ViewDataDictionary<FooModel> viewData = new ViewDataDictionary<FooModel>(model);
+            ViewDataDictionary<string> nestedViewData = MvcHelper.GetNestedViewData(viewData, m => m.foo);
+            HtmlHelper<string> helper = MvcHelper.GetHtmlHelper(nestedViewData);
+            SelectList selectList = new SelectList(MultiSelectListTest.GetSampleStrings());
+
+            // Act
+            MvcHtmlString html = helper.DropDownListFor(m => m, selectList);
+
+            // Assert
+            Assert.Equal(
+                "<select id=\"foo\" name=\"foo\"><option>Alpha</option>" + Environment.NewLine
+              + "<option selected=\"selected\">Bravo</option>" + Environment.NewLine
+              + "<option>Charlie</option>" + Environment.NewLine
+              + "</select>",
+                html.ToHtmlString());
+        }
+
+        [Fact]
+        public void DropDownListForUsesLambdaDefaultValueFromViewDataWhenNested()
+        {
+            // Arrange
+            ViewDataDictionary<FooModel> nestedViewData = MvcHelper.GetNestedViewData(_nestedDropDownListViewData, m => m.inner);
+            HtmlHelper<FooModel> helper = MvcHelper.GetHtmlHelper(nestedViewData);
+            SelectList selectList = new SelectList(MultiSelectListTest.GetSampleStrings());
+
+            // Act
+            MvcHtmlString html = helper.DropDownListFor(m => m.foo, selectList);
+
+            // Assert
+            Assert.Equal(
+                "<select id=\"inner_foo\" name=\"inner.foo\"><option>Alpha</option>" + Environment.NewLine
+              + "<option selected=\"selected\">Bravo</option>" + Environment.NewLine
+              + "<option>Charlie</option>" + Environment.NewLine
+              + "</select>",
+                html.ToHtmlString());
+        }
 
         [Fact]
         public void DropDownListForUsesLambdaDefaultValueWithNullSelectListUsesViewData()
@@ -1215,6 +1258,33 @@ public void DropDownListForUsesLambdaDefaultValueWithNullSelectListUsesViewData(
                 html.ToHtmlString());
         }
 
+        [Fact]
+        public void DropDownListForUsesLambdaDefaultValueWithNullSelectListUsesViewDataWhenNested()
+        {
+            // Arrange
+            FooContainerModel model = new FooContainerModel { inner = new FooModel { foo = "Bravo" } };
+            ViewDataDictionary<FooContainerModel> vdd = new ViewDataDictionary<FooContainerModel>(model)
+            {
+                { "foo", new SelectList(MultiSelectListTest.GetSampleStrings()) }
+            };
+
+            ViewDataDictionary<FooModel> nestedViewData = MvcHelper.GetNestedViewData(vdd, m => m.inner);
+
+
+            HtmlHelper<FooModel> helper = MvcHelper.GetHtmlHelper(nestedViewData);
+
+            // Act
+            MvcHtmlString html = helper.DropDownListFor(m => m.foo, selectList: null);
+
+            // Assert
+            Assert.Equal(
+                "<select id=\"inner_foo\" name=\"inner.foo\"><option>Alpha</option>" + Environment.NewLine
+              + "<option selected=\"selected\">Bravo</option>" + Environment.NewLine
+              + "<option>Charlie</option>" + Environment.NewLine
+              + "</select>",
+                html.ToHtmlString());
+        }
+
         [Fact]
         public void DropDownListForWithAttributesDictionary()
         {
@@ -3330,6 +3400,10 @@ private static IEnumerable<SelectListItem> GetSelectListWithNumericValuesForEnum
             return selectList;
         }
 
+        private class FooContainerModel
+        {
+            public FooModel inner { get; set; }
+        }
         private class FooModel
         {
             public string foo { get; set; }

test/System.Web.Mvc.Test/Util/MvcHelper.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections;
 using System.IO;
+using System.Linq.Expressions;
 using System.Web;
 using System.Web.Mvc;
 using System.Web.Routing;
@@ -152,6 +153,25 @@ public static HttpContextBase GetHttpContext(string appPath, string requestPath,
             return GetHttpContext(appPath, requestPath, httpMethod, Uri.UriSchemeHttp.ToString(), -1);
         }
 
+        public static ViewDataDictionary<TValue> GetNestedViewData<TModel, TValue>(ViewDataDictionary<TModel> viewData, Expression<Func<TModel, TValue>> expression)
+        {
+            var metadata = ModelMetadata.FromLambdaExpression(expression, viewData);
+            var htmlFieldName = ExpressionHelper.GetExpressionText(expression);
+
+
+            ViewDataDictionary nestedViewData = new ViewDataDictionary(viewData)
+            {
+                Model = metadata.Model,
+                ModelMetadata = metadata,
+                TemplateInfo = new TemplateInfo
+                {
+                    HtmlFieldPrefix = viewData.TemplateInfo.GetFullHtmlFieldName(htmlFieldName),
+                }
+            };
+
+            return new ViewDataDictionary<TValue>(nestedViewData);
+        }
+
         public static ViewContext GetViewContextWithPath(string appPath, ViewDataDictionary viewData)
         {
             HttpContextBase httpContext = GetHttpContext(appPath, "/request", "GET");