Add `ModelMetadata` to `ViewData`

- demonstrate `ModelMetadata` is available in a view

Also
- simplify `View()` overloads in `Controller`, pending #110 decisions
- make `Model` in `RazorView<T>` readonly

samples/MvcSample.Web/HomeController.cs

@@ -11,7 +11,26 @@ namespace MvcSample.Web
         }
 
         /// <summary>
-        /// Action that exercises query\form based model binding. 
+        /// Action that shows metadata when model is <c>null</c>.
+        /// </summary>
+        public IActionResult Create()
+        {
+            return View();
+        }
+
+        /// <summary>
+        /// Action that shows metadata when model is non-<c>null</c>.
+        /// </summary>
+        /// <returns></returns>
+        public IActionResult Edit()
+        {
+            ViewBag.Gift = "the banana";
+            ViewData.Model = new User { Name = "Name", Address = "Address in a State", Age = 37, };
+            return View("Create");
+        }
+
+        /// <summary>
+        /// Action that exercises query\form based model binding.
         /// </summary>
         public IActionResult SaveUser(User user)
         {
@@ -55,6 +74,9 @@ namespace MvcSample.Web
             return user;
         }
 
+        /// <summary>
+        /// Action that exercises default view names.
+        /// </summary>
         public IActionResult MyView()
         {
             return View(User());

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

@@ -0,0 +1,42 @@
+@using MvcSample.Web.Models
+@model User
+@{
+    string nullValue = null;
+    ViewBag.Title = (Model == null) ? "Create Page" : "Edit Page";
+    if (ViewData["Gift"] == null)
+    {
+        ViewBag.Gift = "nothing";
+    }
+}
+
+<div class="row">
+    <h2 title="@ViewBag.Title" class="@nullValue">@ViewBag.Title</h2>
+    <h3 title="Thanks" class="@nullValue">Thanks for @ViewBag.Gift</h3>
+    @if (Model == null)
+    {
+        <h4 title ="Null Model" class="@nullValue">Howdy, your model is null.</h4>
+    }
+    else
+    {
+        <h4 title="@Model.Name" class="@nullValue">Hello @Model.Name! Happy @Model.Age birthday.</h4>
+    }
+
+    @{
+        var metadata = ViewData.ModelMetadata;
+        if (metadata != null)
+        {
+            var typeName = metadata.ModelType.Name;
+            var description = metadata.Description;
+            <p>@typeName has description '@description' and contains</p>
+            <ul>
+                @foreach (var property in metadata.Properties)
+                {
+                    var propertyName = property.PropertyName;
+                    var propertyTypeName = property.ModelType.Name;
+                    var propertyDescription = property.Description;
+                    <li>Property @propertyName has type @propertyTypeName and description '@propertyDescription'</li>
+                }
+            </ul>
+        }
+    }
+</div>

src/Microsoft.AspNet.Mvc.Core/ActionResults/ViewResult.cs

@@ -33,9 +33,10 @@ namespace Microsoft.AspNet.Mvc
                 context.HttpContext.Response.ContentType = "text/html";
                 using (var writer = new StreamWriter(context.HttpContext.Response.Body, Encoding.UTF8, 1024, leaveOpen: true))
                 {
-                    var viewContext = new ViewContext(_serviceProvider, context.HttpContext, context.RouteValues, ViewData)
+                    var viewContext = new ViewContext(_serviceProvider, context.HttpContext, context.RouteValues)
                     {
                         Url = new UrlHelper(context.HttpContext, context.Router, context.RouteValues),
+                        ViewData = ViewData,
                         Writer = writer,
                     };
 

src/Microsoft.AspNet.Mvc.Core/Controller.cs

@@ -1,14 +1,15 @@
 using Microsoft.AspNet.Abstractions;
+using Microsoft.AspNet.Mvc.ModelBinding;
 using Microsoft.AspNet.Mvc.Rendering;
 
 namespace Microsoft.AspNet.Mvc
 {
     public class Controller
     {
-        public void Initialize(IActionResultHelper actionResultHelper)
+        public void Initialize(IActionResultHelper actionResultHelper, IModelMetadataProvider metadataProvider)
         {
             Result = actionResultHelper;
-            ViewData = new ViewData<object>();
+            ViewData = new ViewData<object>(metadataProvider);
         }
 
         public IActionResultHelper Result { get; private set; }
@@ -31,21 +32,24 @@ namespace Microsoft.AspNet.Mvc
 
         public IActionResult View(string view)
         {
-            return View(view, model: (object)null);
+            return View(view, model: null);
         }
 
-        public IActionResult View<TModel>(TModel model)
+        // TODO #110: May need <TModel> here and in the overload below.
+        public IActionResult View(object model)
         {
             return View(view: null, model: model);
         }
 
-        public IActionResult View<TModel>(string view, TModel model)
+        public IActionResult View(string view, object model)
         {
-            var viewDataDictionary = new ViewData<TModel>
+            // Do not override ViewData.Model unless passed a non-null value.
+            if (model != null)
             {
-                Model = model
-            };
-            return Result.View(view, viewDataDictionary);
+                ViewData.Model = model;
+            }
+
+            return Result.View(view, ViewData);
         }
     }
 }

src/Microsoft.AspNet.Mvc.Razor/RazorView.cs

@@ -23,7 +23,7 @@ namespace Microsoft.AspNet.Mvc.Razor
 
         private string BodyContent { get; set; }
 
-        public virtual async Task RenderAsync(ViewContext context, TextWriter writer)
+        public virtual async Task RenderAsync([NotNull] ViewContext context, [NotNull] TextWriter writer)
         {
             Context = context;
 

src/Microsoft.AspNet.Mvc.Razor/RazorViewOfT.cs

@@ -1,27 +1,49 @@
 using System.IO;
 using System.Threading.Tasks;
+using Microsoft.AspNet.DependencyInjection;
+using Microsoft.AspNet.Mvc.ModelBinding;
 using Microsoft.AspNet.Mvc.Rendering;
 
 namespace Microsoft.AspNet.Mvc.Razor
 {
     public abstract class RazorView<TModel> : RazorView
     {
-        public TModel Model { get; set; }
+        public TModel Model
+        {
+            get
+            {
+                return ViewData == null ? default(TModel) : ViewData.Model;
+            }
+        }
 
         public dynamic ViewBag
         {
             get { return ViewData; }
         }
 
-        public ViewData<TModel> ViewData { get; set; }
+        public ViewData<TModel> ViewData { get; private set; }
 
         public HtmlHelper<TModel> Html { get; set; }
 
-        public override Task RenderAsync(ViewContext context, TextWriter writer)
+        public override Task RenderAsync([NotNull] ViewContext context, [NotNull] TextWriter writer)
         {
-            var viewData = context.ViewData as ViewData<TModel>;
-            ViewData = viewData ?? new ViewData<TModel>(context.ViewData);
-            Model = ViewData.Model;
+            ViewData = context.ViewData as ViewData<TModel>;
+            if (ViewData == null)
+            {
+                if (context.ViewData != null)
+                {
+                    ViewData = new ViewData<TModel>(context.ViewData);
+                }
+                else
+                {
+                    var metadataProvider = context.ServiceProvider.GetService<IModelMetadataProvider>();
+                    ViewData = new ViewData<TModel>(metadataProvider);
+                }
+
+                // Have new ViewData; make sure it's visible everywhere.
+                context.ViewData = ViewData;
+            }
+
             InitHelpers(context);
 
             return base.RenderAsync(context, writer);

src/Microsoft.AspNet.Mvc.Rendering/View/IView.cs

@@ -5,6 +5,6 @@ namespace Microsoft.AspNet.Mvc.Rendering
 {
     public interface IView
     {
-        Task RenderAsync(ViewContext context, TextWriter writer);
+        Task RenderAsync([NotNull] ViewContext context, [NotNull] TextWriter writer);
     }
 }

src/Microsoft.AspNet.Mvc.Rendering/View/ViewContext.cs

@@ -7,12 +7,11 @@ namespace Microsoft.AspNet.Mvc.Rendering
 {
     public class ViewContext
     {
-        public ViewContext(IServiceProvider serviceProvider, HttpContext httpContext, IDictionary<string, object> viewEngineContext, ViewData viewData)
+        public ViewContext(IServiceProvider serviceProvider, HttpContext httpContext, IDictionary<string, object> viewEngineContext)
         {
             ServiceProvider = serviceProvider;
             HttpContext = httpContext;
             ViewEngineContext = viewEngineContext;
-            ViewData = viewData;
         }
 
         public HttpContext HttpContext { get; private set; }
@@ -21,7 +20,7 @@ namespace Microsoft.AspNet.Mvc.Rendering
 
         public IUrlHelper Url { get; set; }
 
-        public ViewData ViewData { get; private set; }
+        public ViewData ViewData { get; set; }
 
         public IDictionary<string, object> ViewEngineContext { get; private set; }
 

src/Microsoft.AspNet.Mvc.Rendering/View/ViewData.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Dynamic;
+using Microsoft.AspNet.Mvc.ModelBinding;
 
 namespace Microsoft.AspNet.Mvc.Rendering
 {
@@ -8,15 +9,20 @@ namespace Microsoft.AspNet.Mvc.Rendering
     {
         private readonly Dictionary<object, dynamic> _data;
         private object _model;
+        private ModelMetadata _modelMetadata;
+        private IModelMetadataProvider _metadataProvider;
 
-        public ViewData()
+        public ViewData([NotNull] IModelMetadataProvider metadataProvider)
         {
             _data = new Dictionary<object, dynamic>();
+            _metadataProvider = metadataProvider;
         }
 
         public ViewData([NotNull] ViewData source)
         {
             _data = source._data;
+            _modelMetadata = source.ModelMetadata;
+            _metadataProvider = source.MetadataProvider;
             SetModel(source.Model);
         }
 
@@ -44,13 +50,34 @@ namespace Microsoft.AspNet.Mvc.Rendering
             }
             set
             {
-                _data[index] = (dynamic)value;
+                _data[index] = value;
             }
         }
 
+        public virtual ModelMetadata ModelMetadata
+        {
+            get
+            {
+                return _modelMetadata;
+            }
+            set
+            {
+                _modelMetadata = value;
+            }
+        }
+
+        /// <summary>
+        /// Provider for subclasses that need it to override <see cref="ModelMetadata"/>.
+        /// </summary>
+        protected IModelMetadataProvider MetadataProvider
+        {
+            get { return _metadataProvider; }
+        }
+
         public override bool TryGetMember(GetMemberBinder binder, out object result)
         {
             result = _data[binder.Name];
+
             // We return true here because ViewDataDictionary returns null if the key is not
             // in the dictionary, so we simply pass on the returned value.
             return true;
@@ -58,7 +85,7 @@ namespace Microsoft.AspNet.Mvc.Rendering
 
         public override bool TrySetMember(SetMemberBinder binder, object value)
         {
-            // This cast should always succeed assuming TValue is dynamic.
+            // This cast should always succeed.
             dynamic v = value;
             _data[binder.Name] = v;
             return true;
@@ -84,7 +111,8 @@ namespace Microsoft.AspNet.Mvc.Rendering
             }
 
             object index = indexes[0];
-            // This cast should always succeed assuming TValue is dynamic.
+
+            // This cast should always succeed.
             this[(string)index] = value;
             return true;
         }
@@ -95,6 +123,16 @@ namespace Microsoft.AspNet.Mvc.Rendering
         protected virtual void SetModel(object value)
         {
             _model = value;
+            if (value == null)
+            {
+                // Unable to determine model metadata.
+                _modelMetadata = null;
+            }
+            else if (_modelMetadata == null || value.GetType() != ModelMetadata.ModelType)
+            {
+                // Reset or override model metadata based on new value type.
+                _modelMetadata = _metadataProvider.GetMetadataForType(() => value, value.GetType());
+            }
         }
     }
 }

src/Microsoft.AspNet.Mvc.Rendering/View/ViewDataOfTModel.cs

@@ -1,18 +1,32 @@
-using System;
-using Microsoft.AspNet.Mvc.ModelBinding.Internal;
+using System;
+using Microsoft.AspNet.Mvc.ModelBinding;
 
 namespace Microsoft.AspNet.Mvc.Rendering
 {
     public class ViewData<TModel> : ViewData
     {
-        public ViewData()
-            : base()
+        // Fallback ModelMetadata based on TModel. Used when Model is null and base ViewData class is unable to
+        // determine the correct metadata.
+        private readonly ModelMetadata _defaultModelMetadata;
+
+        public ViewData([NotNull] IModelMetadataProvider metadataProvider)
+            : base(metadataProvider)
         {
+            _defaultModelMetadata = MetadataProvider.GetMetadataForType(null, typeof(TModel));
         }
 
-        public ViewData(ViewData source) :
-            base(source)
+        public ViewData(ViewData source)
+            : base(source)
         {
+            var original = source as ViewData<TModel>;
+            if (original != null)
+            {
+                _defaultModelMetadata = original._defaultModelMetadata;
+            }
+            else
+            {
+                _defaultModelMetadata = MetadataProvider.GetMetadataForType(null, typeof(TModel));
+            }
         }
 
         public new TModel Model
@@ -21,6 +35,14 @@ namespace Microsoft.AspNet.Mvc.Rendering
             set { SetModel(value); }
         }
 
+        public override ModelMetadata ModelMetadata
+        {
+            get
+            {
+                return base.ModelMetadata ?? _defaultModelMetadata;
+            }
+        }
+
         protected override void SetModel(object value)
         {
             // IsCompatibleObject verifies if the value is either an instance of TModel or (if value is null) that
@@ -42,6 +64,7 @@ namespace Microsoft.AspNet.Mvc.Rendering
                 {
                     message = Resources.FormatViewData_WrongTModelType(value.GetType(), typeof(TModel));
                 }
+
                 throw new InvalidOperationException(message);
             }
         }

test/Microsoft.AspNet.Mvc.Rendering.Test/ViewDataOfTTest.cs

@@ -1,7 +1,8 @@
 using System;
+using Microsoft.AspNet.Mvc.ModelBinding;
 using Xunit;
 
-namespace Microsoft.AspNet.Mvc.Rendering.Test
+namespace Microsoft.AspNet.Mvc.Rendering
 {
     public class ViewDataOfTTest
     {
@@ -9,7 +10,7 @@ namespace Microsoft.AspNet.Mvc.Rendering.Test
         public void SettingModelThrowsIfTheModelIsNull()
         {
             // Arrange
-            var viewDataOfT = new ViewData<int>();
+            var viewDataOfT = new ViewData<int>(new DataAnnotationsModelMetadataProvider());
             ViewData viewData = viewDataOfT;
 
             // Act and Assert
@@ -21,7 +22,7 @@ namespace Microsoft.AspNet.Mvc.Rendering.Test
         public void SettingModelThrowsIfTheModelIsIncompatible()
         {
             // Arrange
-            var viewDataOfT = new ViewData<string>();
+            var viewDataOfT = new ViewData<string>(new DataAnnotationsModelMetadataProvider());
             ViewData viewData = viewDataOfT;
 
             // Act and Assert
@@ -34,7 +35,7 @@ namespace Microsoft.AspNet.Mvc.Rendering.Test
         {
             // Arrange
             string value = "some value";
-            var viewDataOfT = new ViewData<object>();
+            var viewDataOfT = new ViewData<object>(new DataAnnotationsModelMetadataProvider());
             ViewData viewData = viewDataOfT;
 
             // Act

test/Microsoft.AspNet.Mvc.Rendering.Test/project.json

@@ -3,6 +3,7 @@
   "dependencies": {
     "Microsoft.AspNet.Abstractions": "0.1-alpha-*",
     "Microsoft.AspNet.PipelineCore": "0.1-alpha-*",
+    "Microsoft.AspNet.Mvc.ModelBinding" : "",
     "Microsoft.AspNet.Mvc.Rendering" : "",
     "TestCommon" : "",
     "Xunit.KRunner": "0.1-alpha-*",