Add `ModelMetadata.DisplayName` property

- value comes from `Name` property of `[Display]` attribute
- use new property in `@Html.DisplayName()` and `@Html.Label()`; remove associated TODO comments

src/Microsoft.AspNet.Mvc.Core/Rendering/Html/HtmlHelper.cs

@@ -706,13 +706,11 @@ namespace Microsoft.AspNet.Mvc.Rendering
             // We don't call ModelMetadata.GetDisplayName here because
             // we want to fall back to the field name rather than the ModelType.
             // This is similar to how the GenerateLabel get the text of a label.
-            // TODO: This needs to be updated after ModelMetadata has a DisplayName property
-            var resolvedDisplayName = metadata.PropertyName;
+            var resolvedDisplayName = metadata.DisplayName ?? metadata.PropertyName;
             if (resolvedDisplayName == null)
             {
-                resolvedDisplayName = string.IsNullOrEmpty(htmlFieldName) ?
-                                                                    string.Empty :
-                                                                    htmlFieldName.Split('.').Last();
+                resolvedDisplayName =
+                    string.IsNullOrEmpty(htmlFieldName) ? string.Empty : htmlFieldName.Split('.').Last();
             }
 
             return new HtmlString(Encode(resolvedDisplayName));
@@ -857,13 +855,11 @@ namespace Microsoft.AspNet.Mvc.Rendering
                                                     string labelText,
                                                     object htmlAttributes)
         {
-            // TODO: This needs to be updated after ModelMetadata has a DisplayName property
-            var resolvedLabelText = labelText ?? metadata.PropertyName;
+            var resolvedLabelText = labelText ?? metadata.DisplayName ?? metadata.PropertyName;
             if (resolvedLabelText == null)
             {
-                resolvedLabelText = string.IsNullOrEmpty(htmlFieldName) ?
-                                                                    string.Empty :
-                                                                    htmlFieldName.Split('.').Last();
+                resolvedLabelText =
+                    string.IsNullOrEmpty(htmlFieldName) ? string.Empty : htmlFieldName.Split('.').Last();
             }
 
             if (string.IsNullOrEmpty(resolvedLabelText))

src/Microsoft.AspNet.Mvc.ModelBinding/Metadata/CachedDataAnnotationsModelMetadata.cs

@@ -50,6 +50,23 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
                        : base.ComputeDescription();
         }
 
+        protected override string ComputeDisplayName()
+        {
+            // DisplayName may be provided by DisplayAttribute.
+            // If that does not supply a name, then we fall back to the property name (in base.GetDisplayName()).
+            if (PrototypeCache.Display != null)
+            {
+                // DisplayAttribute doesn't require you to set a name, so this could be null.
+                var name = PrototypeCache.Display.GetName();
+                if (name != null)
+                {
+                    return name;
+                }
+            }
+
+            return base.ComputeDisplayName();
+        }
+
         protected override bool ComputeIsReadOnly()
         {
             if (PrototypeCache.Editable != null)

src/Microsoft.AspNet.Mvc.ModelBinding/Metadata/CachedModelMetadata.cs

@@ -18,6 +18,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
         private bool _convertEmptyStringToNull;
         private string _nullDisplayText;
         private string _description;
+        private string _displayName;
         private bool _isReadOnly;
         private bool _isComplexType;
         private bool _isRequired;
@@ -27,6 +28,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
         private bool _convertEmptyStringToNullComputed;
         private bool _nullDisplayTextComputed;
         private bool _descriptionComputed;
+        private bool _displayNameComputed;
         private bool _isReadOnlyComputed;
         private bool _isComplexTypeComputed;
         private bool _isRequiredComputed;
@@ -113,6 +115,25 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             }
         }
 
+        public sealed override string DisplayName
+        {
+            get
+            {
+                if (!_displayNameComputed)
+                {
+                    _displayName = ComputeDisplayName();
+                    _displayNameComputed = true;
+                }
+
+                return _displayName;
+            }
+            set
+            {
+                _displayName = value;
+                _displayNameComputed = true;
+            }
+        }
+
         public sealed override bool IsReadOnly
         {
             get
@@ -215,6 +236,11 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             return base.Description;
         }
 
+        protected virtual string ComputeDisplayName()
+        {
+            return base.DisplayName;
+        }
+
         protected virtual bool ComputeIsReadOnly()
         {
             return base.IsReadOnly;

src/Microsoft.AspNet.Mvc.ModelBinding/Metadata/ModelMetadata.cs

@@ -60,6 +60,8 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
 
         public virtual string DisplayFormatString { get; set; }
 
+        public virtual string DisplayName { get; set; }
+
         public virtual string EditFormatString { get; set; }
 
         public virtual bool IsComplexType
@@ -205,7 +207,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
 
         public string GetDisplayName()
         {
-            return PropertyName ?? ModelType.Name;
+            return DisplayName ?? PropertyName ?? ModelType.Name;
         }
 
         protected virtual string ComputeSimpleDisplayText()