Add ValidationSummary helper.

This enables Html.ValidationSummary.  This is in reference to WEBFX-97.

samples/MvcSample.Web/HomeController.cs

@@ -10,6 +10,13 @@ namespace MvcSample.Web
             return View("MyView", User());
         }
 
+        public IActionResult ValidationSummary()
+        {
+            ModelState.AddModelError("something", "Something happened, show up in validation summary.");
+
+            return View("ValidationSummary");
+        }
+
         /// <summary>
         /// Action that shows metadata when model is <c>null</c>.
         /// </summary>

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

@@ -0,0 +1,23 @@
+<style>
+    .validationSummary {
+        display: inline-block;
+        padding: 10px;
+        border-radius: 5px;
+        border: 1px solid black;
+        background-color: #e4e3e3;
+    }
+</style>
+
+<h1>ValidationSummary Test Page.</h1>
+<p>Below are all overloads for Html.ValidationSummary.  You should see 5 validation summary titles and 4 validation summary error messages.</p>
+<br />
+
+<section class="validationSummary">
+    @Html.ValidationSummary()
+    @Html.ValidationSummary(excludePropertyErrors: true)
+    @Html.ValidationSummary(message: "Hello from validation message summary 1.")
+    @Html.ValidationSummary(excludePropertyErrors: true, message: "Hello from validation message summary 2")
+    @Html.ValidationSummary(message: "Hello from validation message summary 3", htmlAttributes: new { style = "color: red" })
+    @Html.ValidationSummary(excludePropertyErrors: true, message: "Hello from validation message summary 4", htmlAttributes: new { style = "color: green" })
+    @Html.ValidationSummary(message: "Hello from validation message summary 5", htmlAttributes: new Dictionary<string, object> { { "style", "color: blue" } })
+</section>

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

@@ -7,6 +7,8 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
 {
     public class ModelMetadata
     {
+        public static readonly int DefaultOrder = 10000;
+
         private readonly Type _containerType;
         private readonly Type _modelType;
         private readonly string _propertyName;
@@ -15,6 +17,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
         private bool _convertEmptyStringToNull = true;
         private object _model;
         private Func<object> _modelAccessor;
+        private int _order = DefaultOrder;
         private IEnumerable<ModelMetadata> _properties;
         private Type _realModelType;
 
@@ -57,6 +60,12 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
 
         public virtual bool IsReadOnly { get; set; }
 
+        public virtual int Order
+        {
+            get { return _order; }
+            set { _order = value; }
+        }
+
         public object Model
         {
             get

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

@@ -5,6 +5,7 @@ using System.Globalization;
 using System.IO;
 using System.Net;
 using System.Reflection;
+using System.Text;
 using System.Threading.Tasks;
 using Microsoft.AspNet.Abstractions;
 
@@ -22,6 +23,8 @@ namespace Microsoft.AspNet.Mvc.Rendering
         public static readonly string ValidationSummaryCssClassName = "validation-summary-errors";
         public static readonly string ValidationSummaryValidCssClassName = "validation-summary-valid";
 
+        private const string HiddenListItem = @"<li style=""display:none""></li>";
+
         private ViewContext _viewContext;
         private IViewEngine _viewEngine;
 
@@ -175,6 +178,97 @@ namespace Microsoft.AspNet.Mvc.Rendering
             await viewEngineResult.View.RenderAsync(newViewContext);
         }
 
+        public virtual HtmlString ValidationSummary(bool excludePropertyErrors, string message, IDictionary<string, object> htmlAttributes)
+        {
+            var formContext = ViewContext.ClientValidationEnabled ? ViewContext.FormContext : null;
+
+            if (ViewData.ModelState.IsValid == true)
+            {
+                if (formContext == null ||
+                    ViewContext.UnobtrusiveJavaScriptEnabled &&
+                    excludePropertyErrors)
+                {
+                    // No client side validation/updates
+                    return HtmlString.Empty;
+                }
+            }
+
+            string messageSpan;
+            if (!string.IsNullOrEmpty(message))
+            {
+                var spanTag = new TagBuilder("span");
+                spanTag.SetInnerText(message);
+                messageSpan = spanTag.ToString(TagRenderMode.Normal) + Environment.NewLine;
+            }
+            else
+            {
+                messageSpan = null;
+            }
+
+            var htmlSummary = new StringBuilder();
+            var modelStates = ValidationHelpers.GetModelStateList(ViewData, excludePropertyErrors);
+
+            foreach (var modelState in modelStates)
+            {
+                foreach (var modelError in modelState.Errors)
+                {
+                    string errorText = ValidationHelpers.GetUserErrorMessageOrDefault(modelError, modelState: null);
+
+                    if (!string.IsNullOrEmpty(errorText))
+                    {
+                        var listItem = new TagBuilder("li");
+                        listItem.SetInnerText(errorText);
+                        htmlSummary.AppendLine(listItem.ToString(TagRenderMode.Normal));
+                    }
+                }
+            }
+
+            if (htmlSummary.Length == 0)
+            {
+                htmlSummary.AppendLine(HiddenListItem);
+            }
+
+            var unorderedList = new TagBuilder("ul")
+            {
+                InnerHtml = htmlSummary.ToString()
+            };
+
+            var divBuilder = new TagBuilder("div");
+            divBuilder.MergeAttributes(htmlAttributes);
+
+            if (ViewData.ModelState.IsValid == true)
+            {
+                divBuilder.AddCssClass(HtmlHelper.ValidationSummaryValidCssClassName);
+            }
+            else
+            {
+                divBuilder.AddCssClass(HtmlHelper.ValidationSummaryCssClassName);
+            }
+
+            divBuilder.InnerHtml = messageSpan + unorderedList.ToString(TagRenderMode.Normal);
+
+            if (formContext != null)
+            {
+                if (ViewContext.UnobtrusiveJavaScriptEnabled)
+                {
+                    if (!excludePropertyErrors)
+                    {
+                        // Only put errors in the validation summary if they're supposed to be included there
+                        divBuilder.MergeAttribute("data-valmsg-summary", "true");
+                    }
+                }
+                else
+                {
+                    // client validation summaries need an ID
+                    divBuilder.GenerateId("validationSummary", IdAttributeDotReplacement);
+                    formContext.ValidationSummaryId = divBuilder.Attributes["id"];
+                    formContext.ReplaceValidationSummary = !excludePropertyErrors;
+                }
+            }
+
+            return divBuilder.ToHtmlString(TagRenderMode.Normal);
+        }
+
         /// <summary>
         /// Returns the HTTP method that handles form input (GET or POST) as a string.
         /// </summary>

src/Microsoft.AspNet.Mvc.Rendering/Html/HtmlString.cs

@@ -2,6 +2,8 @@
 {
     public class HtmlString
     {
+        private static readonly HtmlString _empty = new HtmlString(string.Empty);
+
         private readonly string _input;
 
         public HtmlString(string input)
@@ -9,6 +11,14 @@
             _input = input;
         }
 
+        public static HtmlString Empty
+        {
+            get
+            {
+                return _empty;
+            }
+        }
+
         public override string ToString()
         {
             return _input;

src/Microsoft.AspNet.Mvc.Rendering/Html/Validation/ValidationExtensions.cs

@@ -0,0 +1,42 @@
+using System.Collections.Generic;
+
+namespace Microsoft.AspNet.Mvc.Rendering
+{
+    public static class ValidationExtensions
+    {
+        public static HtmlString ValidationSummary<T>(this IHtmlHelper<T> htmlHelper)
+        {
+            return ValidationSummary(htmlHelper, excludePropertyErrors: false);
+        }
+
+        public static HtmlString ValidationSummary<T>(this IHtmlHelper<T> htmlHelper, bool excludePropertyErrors)
+        {
+            return ValidationSummary(htmlHelper, excludePropertyErrors, message: null);
+        }
+
+        public static HtmlString ValidationSummary<T>(this IHtmlHelper<T> htmlHelper, string message)
+        {
+            return ValidationSummary(htmlHelper, excludePropertyErrors: false, message: message, htmlAttributes: (object)null);
+        }
+
+        public static HtmlString ValidationSummary<T>(this IHtmlHelper<T> htmlHelper, bool excludePropertyErrors, string message)
+        {
+            return ValidationSummary(htmlHelper, excludePropertyErrors, message, htmlAttributes: (object)null);
+        }
+
+        public static HtmlString ValidationSummary<T>(this IHtmlHelper<T> htmlHelper, string message, object htmlAttributes)
+        {
+            return ValidationSummary(htmlHelper, excludePropertyErrors: false, message: message, htmlAttributes: HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes));
+        }
+
+        public static HtmlString ValidationSummary<T>(this IHtmlHelper<T> htmlHelper, bool excludePropertyErrors, string message, object htmlAttributes)
+        {
+            return htmlHelper.ValidationSummary(excludePropertyErrors, message, HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes));
+        }
+
+        public static HtmlString ValidationSummary<T>(this IHtmlHelper<T> htmlHelper, string message, IDictionary<string, object> htmlAttributes)
+        {
+            return htmlHelper.ValidationSummary(excludePropertyErrors: false, message: message, htmlAttributes: htmlAttributes);
+        }
+    }
+}

src/Microsoft.AspNet.Mvc.Rendering/Html/Validation/ValidationHelpers.cs

@@ -0,0 +1,65 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.AspNet.Mvc.ModelBinding;
+
+namespace Microsoft.AspNet.Mvc.Rendering
+{
+    internal static class ValidationHelpers
+    {
+        public static string GetUserErrorMessageOrDefault(ModelError modelError, ModelState modelState)
+        {
+            if (!string.IsNullOrEmpty(modelError.ErrorMessage))
+            {
+                return modelError.ErrorMessage;
+            }
+
+            if (modelState == null)
+            {
+                return string.Empty;
+            }
+
+            var attemptedValue = (modelState.Value != null) ? modelState.Value.AttemptedValue : "null";
+
+            return Resources.FormatCommon_ValueNotValidForProperty(attemptedValue);
+        }
+
+        // Returns non-null list of model states, which caller will render in order provided.
+        public static IEnumerable<ModelState> GetModelStateList(ViewDataDictionary viewData, bool excludePropertyErrors)
+        {
+            if (excludePropertyErrors)
+            {
+                ModelState ms;
+                viewData.ModelState.TryGetValue(viewData.TemplateInfo.HtmlFieldPrefix, out ms);
+
+                if (ms != null)
+                {
+                    return new[] { ms };
+                }
+
+                return Enumerable.Empty<ModelState>();
+            }
+            else
+            {
+                // Sort modelStates to respect the ordering in the metadata.                 
+                // ModelState doesn't refer to ModelMetadata, but we can correlate via the property name.
+                var ordering = new Dictionary<string, int>(StringComparer.OrdinalIgnoreCase);
+
+                var metadata = viewData.ModelMetadata;
+                if (metadata != null)
+                {
+                    foreach (var data in metadata.Properties)
+                    {
+                        ordering[data.PropertyName] = data.Order;
+                    }
+
+                    return viewData.ModelState
+                                   .OrderBy(data => ordering[data.Key])
+                                   .Select(ms => ms.Value);
+                }
+
+                return viewData.ModelState.Values;
+            }
+        }
+    }
+}

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

@@ -1,5 +1,6 @@
 using System;
 using System.Linq.Expressions;
+using System.Collections.Generic;
 using System.Threading.Tasks;
 
 namespace Microsoft.AspNet.Mvc.Rendering
@@ -99,5 +100,14 @@ namespace Microsoft.AspNet.Mvc.Rendering
         /// <param name="viewData">A <see cref="ViewDataDictionary"/> to pass into the partial view.</param>
         /// <returns>A task that represents when rendering has completed.</returns>
         Task RenderPartialAsync([NotNull] string partialViewName, object model, ViewDataDictionary viewData);
+
+        /// <summary>
+        /// Returns an unordered list (ul element) of validation messages that are in the <see cref="ModelStateDictionary"/> object.
+        /// </summary>
+        /// <param name="excludePropertyErrors">true to have the summary display model-level errors only, or false to have the summary display all errors.</param>
+        /// <param name="message">The message to display with the validation summary.</param>
+        /// <param name="htmlAttributes">A dictionary that contains the HTML attributes for the element.</param>
+        /// <returns>An <see cref="HtmlString"/> that contains an unordered list (ul element) of validation messages.</returns>
+        HtmlString ValidationSummary(bool excludePropertyErrors, string message, IDictionary<string, object> htmlAttributes);
     }
 }

src/Microsoft.AspNet.Mvc.Rendering/Properties/Resources.Designer.cs

@@ -74,6 +74,22 @@ namespace Microsoft.AspNet.Mvc.Rendering
             return string.Format(CultureInfo.CurrentCulture, GetString("Common_PartialViewNotFound"), p0, p1);
         }
 
+        /// <summary>
+        /// The value '{0}' is invalid.
+        /// </summary>
+        internal static string Common_ValueNotValidForProperty
+        {
+            get { return GetString("Common_ValueNotValidForProperty"); }
+        }
+
+        /// <summary>
+        /// The value '{0}' is invalid.
+        /// </summary>
+        internal static string FormatCommon_ValueNotValidForProperty(object p0)
+        {
+            return string.Format(CultureInfo.CurrentCulture, GetString("Common_ValueNotValidForProperty"), p0);
+        }
+
         /// <summary>
         /// ViewData value must not be null.
         /// </summary>

src/Microsoft.AspNet.Mvc.Rendering/Properties/Resources.resx

@@ -129,6 +129,9 @@
   <data name="Common_PartialViewNotFound" xml:space="preserve">
     <value>The partial view '{0}' was not found or no view engine supports the searched locations. The following locations were searched:{1}</value>
   </data>
+  <data name="Common_ValueNotValidForProperty" xml:space="preserve">
+    <value>The value '{0}' is invalid.</value>
+  </data>
   <data name="DynamicViewData_ViewDataNull" xml:space="preserve">
     <value>ViewData value must not be null.</value>
   </data>

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

@@ -16,7 +16,10 @@ namespace Microsoft.AspNet.Mvc.Rendering
         
         public ViewContext([NotNull] ViewContext viewContext)
             : this(viewContext.ServiceProvider, viewContext.HttpContext, viewContext.ViewEngineContext)
-        { }
+        {
+            UnobtrusiveJavaScriptEnabled = viewContext.UnobtrusiveJavaScriptEnabled;
+            ClientValidationEnabled = viewContext.ClientValidationEnabled;
+        }
 
         public ViewContext(IServiceProvider serviceProvider, HttpContext httpContext,
             IDictionary<string, object> viewEngineContext)
@@ -25,6 +28,8 @@ namespace Microsoft.AspNet.Mvc.Rendering
             HttpContext = httpContext;
             ViewEngineContext = viewEngineContext;
             _formContext = _defaultFormContext;
+            UnobtrusiveJavaScriptEnabled = true;
+            ClientValidationEnabled = true;
         }
 
         public IViewComponentHelper Component { get; set; }
@@ -48,6 +53,10 @@ namespace Microsoft.AspNet.Mvc.Rendering
 
         public IUrlHelper Url { get; set; }
 
+        public bool UnobtrusiveJavaScriptEnabled { get; set; }
+
+        public bool ClientValidationEnabled { get; set; }
+
         public dynamic ViewBag
         {
             get