Introducing DisplayText, DisplayTextFor, Id, IdFor, IdForModel.

Fixing CachedDataAnnotationsModelMetadata to support NullDisplayText.

samples/MvcSample.Web/HomeController.cs

@@ -96,7 +96,8 @@ namespace MvcSample.Web
                     Address = "Dependents address",
                     Alive = false,
                 },
-                About = "I am a Software Engineer"
+                Profession = "Software Engineer",
+                About = "I like playing Football"
             };
 
             return user;

samples/MvcSample.Web/Models/User.cs

@@ -13,6 +13,8 @@ namespace MvcSample.Web.Models
         public User Dependent { get; set; }
         public bool Alive { get; set; }
         public string Password { get; set; }
+        [DisplayFormat(ConvertEmptyStringToNull = true, NullDisplayText = "You can explain about your profession")]
+        public string Profession { get; set; }
         public string About { get; set; }
         public string Log { get; set; }
     }

samples/MvcSample.Web/Views/Home/Create.cshtml

@@ -18,7 +18,7 @@
     }
     else
     {
-        <h4 title="@Model.Name" class="@ViewBag.NullValue">Hello @Model.Name! Happy @(Model.Age)th birthday.</h4>
+        <h4 title="@Model.Name" class="@ViewBag.NullValue">Hello @Html.DisplayTextFor(model => model.Name)! Happy @(Model.Age)th birthday.</h4>
     }
 
     @{
@@ -69,10 +69,18 @@
                 </tr>
                 <tr>
                     <td>
-                        <label class="control-label col-md-2">Model.Name</label>
+                        <label class="control-label col-md-2">Model.Profession</label>
                     </td>
                     <td>
-                        @Html.TextArea("About", "You can explain about your profession, hobbies etc.", 5, 40, htmlAttributes: new { style = "font-weight:bold" })
+                        <input type="text" id="@Html.IdFor(model => model.Profession)" name="Profession" value='@Html.DisplayText("Profession")' />
+                    </td>
+                </tr>
+                <tr>
+                    <td>
+                        <label class="control-label col-md-2">Model.About</label>
+                    </td>
+                    <td>
+                        @Html.TextArea("About", "You can explain about your hobbies, work etc.", 5, 40, htmlAttributes: new { style = "font-weight:bold" })
                     </td>
                 </tr>
                 <tr>

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

@@ -258,6 +258,13 @@ namespace Microsoft.AspNet.Mvc.Rendering
             return GenerateDisplayName(metadata, expression);
         }
 
+        /// <inheritdoc />
+        public HtmlString DisplayText(string name)
+        {
+            var metadata = ExpressionMetadataProvider.FromStringExpression(name, ViewData, MetadataProvider);
+
+            return GenerateDisplayText(metadata);
+        }
 
         /// <inheritdoc />
         public HtmlString DropDownList(string name, IEnumerable<SelectListItem> selectList, string optionLabel,
@@ -291,6 +298,12 @@ namespace Microsoft.AspNet.Mvc.Rendering
                 htmlAttributes: htmlAttributes);
         }
 
+        /// <inheritdoc />
+        public HtmlString Id(string name)
+        {
+            return GenerateId(name);
+        }
+
         /// <inheritdoc />
         public HtmlString Label(string expression, string labelText, object htmlAttributes)
         {
@@ -652,6 +665,11 @@ namespace Microsoft.AspNet.Mvc.Rendering
 
             return new HtmlString(Encode(resolvedDisplayName));
         }
+        
+        protected virtual HtmlString GenerateDisplayText(ModelMetadata metadata)
+        {
+            return new HtmlString(metadata.SimpleDisplayText);
+        }
 
         protected HtmlString GenerateDropDown(ModelMetadata metadata, string expression,
             IEnumerable<SelectListItem> selectList, string optionLabel, object htmlAttributes)
@@ -760,6 +778,11 @@ namespace Microsoft.AspNet.Mvc.Rendering
                 htmlAttributes: htmlAttributeDictionary);
         }
 
+        protected virtual HtmlString GenerateId(string expression)
+        {
+            return new HtmlString(Encode(ViewData.TemplateInfo.GetFullHtmlFieldName(expression)));
+        }
+
         protected virtual HtmlString GenerateLabel([NotNull] ModelMetadata metadata, 
                                                     string htmlFieldName,
                                                     string labelText,

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

@@ -108,6 +108,12 @@ namespace Microsoft.AspNet.Mvc.Rendering
 
             return GenerateDisplayName(metadata, expressionText);
         }
+        
+        /// <inheritdoc />
+        public HtmlString DisplayTextFor<TValue>([NotNull] Expression<Func<TModel, TValue>> expression)
+        {
+            return GenerateDisplayText(GetModelMetadata(expression));
+        }
 
         /// <inheritdoc />
         public HtmlString EditorFor<TValue>(
@@ -134,6 +140,12 @@ namespace Microsoft.AspNet.Mvc.Rendering
                 htmlAttributes: htmlAttributes);
         }
 
+        /// <inheritdoc />
+        public HtmlString IdFor<TProperty>([NotNull] Expression<Func<TModel, TProperty>> expression)
+        {
+            return GenerateId(GetExpressionName(expression));
+        }
+
         /// <inheritdoc />
         public HtmlString LabelFor<TValue>([NotNull] Expression<Func<TModel, TValue>> expression, string labelText, object htmlAttributes)
         {

src/Microsoft.AspNet.Mvc.Core/Rendering/HtmlHelperNameExtensions.cs

@@ -15,5 +15,15 @@ namespace Microsoft.AspNet.Mvc.Rendering
         {
             return htmlHelper.Name(string.Empty);
         }
+
+        /// <summary>
+        /// Gets the full HTML field id for the current model.
+        /// </summary>
+        /// <param name="htmlHelper">The <see cref="HtmlHelper"/> instance that this method extends.</param>
+        /// <returns>An <see cref="HtmlString"/> that represents HTML markup.</returns>
+        public static HtmlString IdForModel([NotNull] this IHtmlHelper htmlHelper)
+        {
+            return htmlHelper.Id(string.Empty);
+        }
     }
 }

src/Microsoft.AspNet.Mvc.Core/Rendering/IHtmlHelper.cs

@@ -161,6 +161,16 @@ namespace Microsoft.AspNet.Mvc.Rendering
         /// </returns>
         HtmlString DisplayName(string expression);
 
+        /// Returns the HtmlString corresponding to the property in the model specified by the name.
+        /// </summary>
+        /// <param name="name">
+        /// The string which identifies the object for which the HtmlString should be returned.</param>
+        /// <returns>
+        /// New <see cref="HtmlString"/> containing the display text. If the value is null,
+        /// then it returns the ModelMetadata.NullDisplayText.
+        /// </returns>
+        HtmlString DisplayText(string name);
+
         /// <summary>
         /// Returns a single-selection HTML {select} element using the specified name of the form field,
         /// list items, option label, and HTML attributes.
@@ -248,6 +258,13 @@ namespace Microsoft.AspNet.Mvc.Rendering
         /// <returns>New <see cref="HtmlString"/> containing the rendered HTML.</returns>
         HtmlString Hidden(string name, object value, object htmlAttributes);
 
+        /// <summary>
+        /// Gets the Id of the given string.
+        /// </summary>
+        /// <param name="name">The string which identifies the object for which the Id should be returned.</param>
+        /// <returns>New <see cref="HtmlString"/> containing the Id.</returns>
+        HtmlString Id(string name);
+
         /// <summary>
         /// Returns an HTML label element and the property name of the property that is represented by the specified
         /// expression.

src/Microsoft.AspNet.Mvc.Core/Rendering/IHtmlHelperOfT.cs

@@ -70,6 +70,18 @@ namespace Microsoft.AspNet.Mvc.Rendering
         HtmlString DisplayNameForInnerType<TInnerModel, TValue>(
             [NotNull] Expression<Func<TInnerModel, TValue>> expression);
 
+        /// <summary>
+        /// Returns the HtmlString corresponding to the expression specified.
+        /// </summary>
+        /// <param name="expression">
+        /// The expression identifies the object for which the HtmlString should be returned.
+        /// </param>
+        /// <returns>
+        /// New <see cref="HtmlString"/> containing the display text. If the value is null,
+        /// then it returns the ModelMetadata.NullDisplayText.
+        /// </returns>
+        HtmlString DisplayTextFor<TValue>([NotNull] Expression<Func<TModel, TValue>> expression);
+
         /// <summary>
         /// Returns a single-selection HTML {select} element for the object that is represented
         /// by the specified expression using the specified list items, option label, and HTML attributes.
@@ -125,6 +137,13 @@ namespace Microsoft.AspNet.Mvc.Rendering
         HtmlString HiddenFor<TProperty>([NotNull] Expression<Func<TModel, TProperty>> expression,
             object htmlAttributes);
 
+        /// <summary>
+        /// Gets the Id of the given expression.
+        /// </summary>
+        /// <param name="expression">The expression identifies the object for which the Id should be returned.</param>
+        /// <returns>New <see cref="HtmlString"/> containing the Id.</returns>
+        HtmlString IdFor<TProperty>([NotNull] Expression<Func<TModel, TProperty>> expression);
+
         /// <summary>
         /// Returns an HTML label element and the property name of the property that is represented by the specified
         /// expression.

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

@@ -31,6 +31,13 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
                        : base.ComputeConvertEmptyStringToNull();
         }
 
+        protected override string ComputeNullDisplayText()
+        {
+            return PrototypeCache.DisplayFormat != null
+                       ? PrototypeCache.DisplayFormat.NullDisplayText
+                       : base.ComputeNullDisplayText();
+        }
+
         protected override string ComputeDescription()
         {
             return PrototypeCache.Display != null

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

@@ -17,11 +17,13 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
     public abstract class CachedModelMetadata<TPrototypeCache> : ModelMetadata
     {
         private bool _convertEmptyStringToNull;
+        private string _nullDisplayText;
         private string _description;
         private bool _isReadOnly;
         private bool _isComplexType;
 
         private bool _convertEmptyStringToNullComputed;
+        private bool _nullDisplayTextComputed;
         private bool _descriptionComputed;
         private bool _isReadOnlyComputed;
         private bool _isComplexTypeComputed;
@@ -62,6 +64,24 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             }
         }
 
+        public sealed override string NullDisplayText
+        {
+            get
+            {
+                if (!_nullDisplayTextComputed)
+                {
+                    _nullDisplayText = ComputeNullDisplayText();
+                    _nullDisplayTextComputed = true;
+                }
+                return _nullDisplayText;
+            }
+            set
+            {
+                _nullDisplayText = value;
+                _nullDisplayTextComputed = true;
+            }
+        }
+
         public sealed override string Description
         {
             get
@@ -118,6 +138,11 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             return base.ConvertEmptyStringToNull;
         }
 
+        protected virtual string ComputeNullDisplayText()
+        {
+            return base.NullDisplayText;
+        }
+
         protected virtual string ComputeDescription()
         {
             return base.Description;

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

@@ -1,6 +1,8 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
+using System.Globalization;
+using System.Linq;
 using Microsoft.AspNet.Mvc.ModelBinding.Internal;
 
 namespace Microsoft.AspNet.Mvc.ModelBinding
@@ -20,6 +22,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
         private int _order = DefaultOrder;
         private IEnumerable<ModelMetadata> _properties;
         private Type _realModelType;
+        private string _simpleDisplayText;
 
         public ModelMetadata([NotNull] IModelMetadataProvider provider, 
                              Type containerType, 
@@ -141,6 +144,21 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             }
         }
 
+        public virtual string SimpleDisplayText
+        {
+            get
+            {
+                if (_simpleDisplayText == null)
+                {
+                    _simpleDisplayText = ComputeSimpleDisplayText();
+                }
+
+                return _simpleDisplayText;
+            }
+
+            set { _simpleDisplayText = value; }
+        }
+
         public virtual string TemplateHint { get; set; }
 
         internal EfficientTypePropertyKey<Type, string> CacheKey
@@ -177,6 +195,38 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
         //    return validatorProviders.SelectMany(provider => provider.GetValidators(this, validatorProviders));
         //}
 
+        protected virtual string ComputeSimpleDisplayText()
+        {
+            if (Model == null)
+            {
+                return NullDisplayText;
+            }
+
+            var stringResult = Convert.ToString(Model, CultureInfo.CurrentCulture);
+            if (stringResult == null)
+            {
+                return string.Empty;
+            }
+
+            if (!stringResult.Equals(Model.GetType().FullName, StringComparison.Ordinal))
+            {
+                return stringResult;
+            }
+
+            var firstProperty = Properties.FirstOrDefault();
+            if (firstProperty == null)
+            {
+                return string.Empty;
+            }
+
+            if (firstProperty.Model == null)
+            {
+                return firstProperty.NullDisplayText;
+            }
+
+            return Convert.ToString(firstProperty.Model, CultureInfo.CurrentCulture);
+        }
+
         private static EfficientTypePropertyKey<Type, string> CreateCacheKey(Type containerType, Type modelType, string propertyName)
         {
             // If metadata is for a property then containerType != null && propertyName != null

test/Microsoft.AspNet.Mvc.ModelBinding.Test/Metadata/ModelMetadataTest.cs

@@ -25,6 +25,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding.Test
             // Assert
             Assert.Equal(typeof(Exception), metadata.ContainerType);
             Assert.True(metadata.ConvertEmptyStringToNull);
+            Assert.Null(metadata.NullDisplayText);
             Assert.Null(metadata.Description);
             Assert.Equal("model", metadata.Model);
             Assert.Equal(typeof(string), metadata.ModelType);