1 files changed, 80 insertions, 0 deletions
diff --git a/src/System.Web.Mvc/Html/ValueExtensions.cs b/src/System.Web.Mvc/Html/ValueExtensions.cs
new file mode 100644
index 00000000..53e297c7
--- /dev/null
+++ b/src/System.Web.Mvc/Html/ValueExtensions.cs
@@ -0,0 +1,80 @@
+using System.Diagnostics.CodeAnalysis;
+using System.Linq.Expressions;
+
+namespace System.Web.Mvc.Html
+{
+    public static class ValueExtensions
+    {
+        public static MvcHtmlString Value(this HtmlHelper html, string name)
+        {
+            return Value(html, name, format: null);
+        }
+
+        public static MvcHtmlString Value(this HtmlHelper html, string name, string format)
+        {
+            if (name == null)
+            {
+                throw new ArgumentNullException("name");
+            }
+
+            return ValueForHelper(html, name, value: null, format: format, useViewData: true);
+        }
+
+        [SuppressMessage("Microsoft.Design", "CA1006:DoNotNestGenericTypesInMemberSignatures", Justification = "This is an appropriate nesting of generic types")]
+        public static MvcHtmlString ValueFor<TModel, TProperty>(this HtmlHelper<TModel> html, Expression<Func<TModel, TProperty>> expression)
+        {
+            return ValueFor(html, expression, format: null);
+        }
+
+        [SuppressMessage("Microsoft.Design", "CA1006:DoNotNestGenericTypesInMemberSignatures", Justification = "This is an appropriate nesting of generic types")]
+        public static MvcHtmlString ValueFor<TModel, TProperty>(this HtmlHelper<TModel> html, Expression<Func<TModel, TProperty>> expression, string format)
+        {
+            ModelMetadata metadata = ModelMetadata.FromLambdaExpression(expression, html.ViewData);
+            return ValueForHelper(html, ExpressionHelper.GetExpressionText(expression), metadata.Model, format, useViewData: false);
+        }
+
+        public static MvcHtmlString ValueForModel(this HtmlHelper html)
+        {
+            return ValueForModel(html, format: null);
+        }
+
+        public static MvcHtmlString ValueForModel(this HtmlHelper html, string format)
+        {
+            return Value(html, String.Empty, format);
+        }
+
+        internal static MvcHtmlString ValueForHelper(HtmlHelper html, string name, object value, string format, bool useViewData)
+        {
+            string fullName = html.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(name);
+            string attemptedValue = (string)html.GetModelStateValue(fullName, typeof(string));
+            string resolvedValue;
+
+            if (attemptedValue != null)
+            {
+                // case 1: if ModelState has a value then it's already formatted so ignore format string
+                resolvedValue = attemptedValue;
+            }
+            else if (useViewData)
+            {
+                if (name.Length == 0)
+                {
+                    // case 2(a): format the value from ModelMetadata for the current model
+                    ModelMetadata metadata = ModelMetadata.FromStringExpression(String.Empty, html.ViewContext.ViewData);
+                    resolvedValue = html.FormatValue(metadata.Model, format);
+                }
+                else
+                {
+                    // case 2(b): format the value from ViewData
+                    resolvedValue = html.EvalString(name, format);
+                }
+            }
+            else
+            {
+                // case 3: format the explicit value from ModelMetadata
+                resolvedValue = html.FormatValue(value, format);
+            }
+
+            return MvcHtmlString.Create(html.AttributeEncode(resolvedValue));
+        }
+    }
+}