Add `ModelBindingResult.IsFatalError` and make body binding more consistent

- part I of II for #2445 (with a duplicate code PR to follow)
- needed for #2445 because new `ModelState` entries for values will make inconsisteny worse
- change `BodyModelBinder` to use same keys for all `ModelBindingResult`s and `ModelState` entries
 - return fatal error result if formatter adds an error to `ModelState`
 - update potential callers to avoid avoid ignoring `IsFatalError`
- fix test attempting to serialize all of `ModelState`
 - will be borked with additional `RawValue`s in state
- fix two other tests that serialized `ModelState` but checked only `IsValid`

nits:
- address minor inconsistencies in `ModelBindingContext`
- use `System.Reflection.Extensions` package a bit more, where it's already referenced
- remove some unused resources

src/Microsoft.AspNet.Mvc.Abstractions/ModelBinding/ModelBindingContext.cs

@@ -39,16 +39,20 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             [NotNull] string modelName,
             [NotNull] ModelMetadata modelMetadata)
         {
-            var modelBindingContext = new ModelBindingContext();
+            var modelBindingContext = new ModelBindingContext
-            modelBindingContext.ModelName = modelName;
+            {
-            modelBindingContext.ModelMetadata = modelMetadata;
+                ModelName = modelName,
-            modelBindingContext.ModelState = bindingContext.ModelState;
+                ModelMetadata = modelMetadata,
-            modelBindingContext.ValueProvider = bindingContext.ValueProvider;
+
-            modelBindingContext.OperationBindingContext = bindingContext.OperationBindingContext;
+                ModelState = bindingContext.ModelState,
+                ValueProvider = bindingContext.ValueProvider,
+                OperationBindingContext = bindingContext.OperationBindingContext,
+
+                BindingSource = modelMetadata.BindingSource,
+                BinderModelName = modelMetadata.BinderModelName,
+                BinderType = modelMetadata.BinderType,
+            };
 
-            modelBindingContext.BindingSource = modelMetadata.BindingSource;
-            modelBindingContext.BinderModelName = modelMetadata.BinderModelName;
-            modelBindingContext.BinderType = modelMetadata.BinderType;
             return modelBindingContext;
         }
 
@@ -68,7 +72,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             var binderModelName = bindingInfo?.BinderModelName ?? metadata.BinderModelName;
             var propertyPredicateProvider =
                 bindingInfo?.PropertyBindingPredicateProvider ?? metadata.PropertyBindingPredicateProvider;
-            return new ModelBindingContext()
+            return new ModelBindingContext
             {
                 ModelMetadata = metadata,
                 BindingSource = bindingInfo?.BindingSource ?? metadata.BindingSource,
@@ -168,8 +172,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
 
         /// <summary>
         /// Gets or sets a value that indicates whether the binder should use an empty prefix to look up
-        /// values in <see cref="IValueProvider"/> when no values are found using the
+        /// values in <see cref="IValueProvider"/> when no values are found using the <see cref="ModelName"/> prefix.
-        /// <see cref="ModelName"/> prefix.
         /// </summary>
         public bool FallbackToEmptyPrefix { get; set; }
 

src/Microsoft.AspNet.Mvc.Abstractions/ModelBinding/ModelBindingResult.cs

@@ -8,6 +8,16 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
     /// </summary>
     public class ModelBindingResult
     {
+        /// <summary>
+        /// Creates a new <see cref="ModelBindingResult"/> indicating a fatal error.
+        /// </summary>
+        /// <param name="key">The key using which was used to attempt binding the model.</param>
+        public ModelBindingResult(string key)
+        {
+            Key = key;
+            IsFatalError = true;
+        }
+
         /// <summary>
         /// Creates a new <see cref="ModelBindingResult"/>.
         /// </summary>
@@ -16,7 +26,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
         /// <param name="isModelSet">A value that represents if the model has been set by the
         /// <see cref="IModelBinder"/>.</param>
         public ModelBindingResult(object model, string key, bool isModelSet)
-            : this (model, key, isModelSet, validationNode: null)
+            : this(model, key, isModelSet, validationNode: null)
         {
         }
 
@@ -52,6 +62,12 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
         /// </summary>
         public string Key { get; }
 
+        /// <summary>
+        /// Gets a value indicating the caller should not attempt binding again. This attempt encountered a fatal
+        /// error.
+        /// </summary>
+        public bool IsFatalError { get; }
+
         /// <summary>
         /// <para>
         /// Gets a value indicating whether or not the <see cref="Model"/> value has been set.

src/Microsoft.AspNet.Mvc.Core/ModelBinding/BinderTypeBasedModelBinder.cs

@@ -46,7 +46,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             var result = await modelBinder.BindModelAsync(bindingContext);
 
             var modelBindingResult = result != null ?
-                new ModelBindingResult(result.Model, result.Key, result.IsModelSet, result.ValidationNode) :
+                result :
                 new ModelBindingResult(model: null, key: bindingContext.ModelName, isModelSet: false);
 
             // A model binder was specified by metadata and this binder handles all such cases.

src/Microsoft.AspNet.Mvc.Core/ModelBinding/BindingSourceModelBinder.cs

@@ -79,10 +79,9 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
 
             var result = await BindModelCoreAsync(context);
 
-            var modelBindingResult =
+            var modelBindingResult = result != null ?
-                result != null ?
+                result :
-                    new ModelBindingResult(result.Model, result.Key, result.IsModelSet, result.ValidationNode) :
+                new ModelBindingResult(model: null, key: context.ModelName, isModelSet: false);
-                    new ModelBindingResult(model: null, key: context.ModelName, isModelSet: false);
 
             // This model binder is the only handler for its binding source.
             // Always tell the model binding system to skip other model binders i.e. return non-null.

src/Microsoft.AspNet.Mvc.Core/ModelBinding/BodyModelBinder.cs

@@ -5,7 +5,6 @@ using System;
 using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.AspNet.Mvc.Core;
-using Microsoft.Framework.DependencyInjection;
 using Microsoft.Framework.Internal;
 
 namespace Microsoft.AspNet.Mvc.ModelBinding
@@ -28,36 +27,45 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
         protected async override Task<ModelBindingResult> BindModelCoreAsync(
             [NotNull] ModelBindingContext bindingContext)
         {
+            // For compatibility with MVC 5.0 for top level object we want to consider an empty key instead of
+            // the parameter name/a custom name. In all other cases (like when binding body to a property) we
+            // consider the entire ModelName as a prefix.
+            var isTopLevelObject = bindingContext.ModelMetadata.ContainerType == null;
+            var modelBindingKey = isTopLevelObject ? string.Empty : bindingContext.ModelName;
+
             var httpContext = bindingContext.OperationBindingContext.HttpContext;
-            var formatters = bindingContext.OperationBindingContext.InputFormatters;
 
             var formatterContext = new InputFormatterContext(
                 httpContext,
                 bindingContext.ModelState,
                 bindingContext.ModelType);
+            var formatters = bindingContext.OperationBindingContext.InputFormatters;
             var formatter = formatters.FirstOrDefault(f => f.CanRead(formatterContext));
 
             if (formatter == null)
             {
                 var unsupportedContentType = Resources.FormatUnsupportedContentType(
                     bindingContext.OperationBindingContext.HttpContext.Request.ContentType);
-                bindingContext.ModelState.AddModelError(bindingContext.ModelName, unsupportedContentType);
+                bindingContext.ModelState.AddModelError(modelBindingKey, unsupportedContentType);
 
-                // This model binder is the only handler for the Body binding source.
+                // This model binder is the only handler for the Body binding source and it cannot run twice. Always
-                // Always tell the model binding system to skip other model binders i.e. return non-null.
+                // tell the model binding system to skip other model binders and never to fall back i.e. indicate a
-                return new ModelBindingResult(model: null, key: bindingContext.ModelName, isModelSet: false);
+                // fatal error.
+                return new ModelBindingResult(modelBindingKey);
             }
 
             try
             {
+                var previousCount = bindingContext.ModelState.ErrorCount;
                 var model = await formatter.ReadAsync(formatterContext);
 
-                var isTopLevelObject = bindingContext.ModelMetadata.ContainerType == null;
+                if (bindingContext.ModelState.ErrorCount != previousCount)
+                {
+                    // Formatter added an error. Do not use the model it returned. As above, tell the model binding
+                    // system to skip other model binders and never to fall back.
+                    return new ModelBindingResult(modelBindingKey);
+                }
 
-                // For compatibility with MVC 5.0 for top level object we want to consider an empty key instead of
-                // the parameter name/a custom name. In all other cases (like when binding body to a property) we
-                // consider the entire ModelName as a prefix.
-                var modelBindingKey = isTopLevelObject ? string.Empty : bindingContext.ModelName;
 
                 var validationNode = new ModelValidationNode(modelBindingKey, bindingContext.ModelMetadata, model)
                 {
@@ -72,11 +80,12 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             }
             catch (Exception ex)
             {
-                bindingContext.ModelState.AddModelError(bindingContext.ModelName, ex);
+                bindingContext.ModelState.AddModelError(modelBindingKey, ex);
 
-                // This model binder is the only handler for the Body binding source.
+                // This model binder is the only handler for the Body binding source and it cannot run twice. Always
-                // Always tell the model binding system to skip other model binders i.e. return non-null.
+                // tell the model binding system to skip other model binders and never to fall back i.e. indicate a
-                return new ModelBindingResult(model: null, key: bindingContext.ModelName, isModelSet: false);
+                // fatal error.
+                return new ModelBindingResult(modelBindingKey);
             }
         }
     }

src/Microsoft.AspNet.Mvc.Core/ModelBinding/CompositeModelBinder.cs

@@ -42,8 +42,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
                 !string.IsNullOrEmpty(bindingContext.ModelName))
             {
                 // Fall back to empty prefix.
-                newBindingContext = CreateNewBindingContext(bindingContext,
+                newBindingContext = CreateNewBindingContext(bindingContext, modelName: string.Empty);
-                                                            modelName: string.Empty);
                 modelBindingResult = await TryBind(newBindingContext);
             }
 
@@ -99,13 +98,19 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
                 var result = await binder.BindModelAsync(bindingContext);
                 if (result != null)
                 {
-                    // Use returned ModelBindingResult if it either indicates the model was set or is related to a
+                    // Use returned ModelBindingResult if it indicates the model was set, indicates the binder
-                    // ModelState entry. The second condition is necessary because the ModelState entry would never be
+                    // encountered a fatal error, or is related to a ModelState entry.
-                    // validated if caller fell back to the empty prefix, leading to an possibly-incorrect !IsValid.
                     //
-                    // In most (hopefully all) cases, the ModelState entry exists because some binders add errors
+                    // The second condition is necessary because the BodyModelBinder unconditionally binds during the
-                    // before returning a result with !IsModelSet. Those binders often cannot run twice anyhow.
+                    // first attempt and does not always create ModelState values using ModelName.
-                    if (result.IsModelSet || bindingContext.ModelState.ContainsKey(bindingContext.ModelName))
+                    //
+                    // The third condition is necessary because the ModelState entry would never be validated if
+                    // caller fell back to the empty prefix, leading to an possibly-incorrect !IsValid. In most
+                    // (hopefully all) cases, the ModelState entry exists because some binders add errors before
+                    // returning a result with !IsModelSet. Those binders often cannot run twice anyhow.
+                    if (result.IsFatalError ||
+                        result.IsModelSet ||
+                        bindingContext.ModelState.ContainsKey(bindingContext.ModelName))
                     {
                         return result;
                     }
@@ -121,8 +126,9 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             return null;
         }
 
-        private static ModelBindingContext CreateNewBindingContext(ModelBindingContext oldBindingContext,
+        private static ModelBindingContext CreateNewBindingContext(
-                                                                   string modelName)
+            ModelBindingContext oldBindingContext,
+            string modelName)
         {
             var newBindingContext = new ModelBindingContext
             {

src/Microsoft.AspNet.Mvc.Core/ModelBinding/GenericModelBinder.cs

@@ -20,7 +20,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
                 var result = await binder.BindModelAsync(bindingContext);
 
                 var modelBindingResult = result != null ?
-                    new ModelBindingResult(result.Model, result.Key, result.IsModelSet, result.ValidationNode) :
+                    result :
                     new ModelBindingResult(model: null, key: bindingContext.ModelName, isModelSet: false);
 
                 // Were able to resolve a binder type.

src/Microsoft.AspNet.Mvc.Core/ModelBinding/HeaderModelBinder.cs

@@ -2,7 +2,9 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System.Collections.Generic;
+#if DNXCORE50
 using System.Reflection;
+#endif
 using System.Threading.Tasks;
 using Microsoft.Framework.Internal;
 
@@ -39,8 +41,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
                     model = value;
                 }
             }
-            else if (typeof(IEnumerable<string>).GetTypeInfo().IsAssignableFrom(
+            else if (typeof(IEnumerable<string>).IsAssignableFrom(bindingContext.ModelType))
-                bindingContext.ModelType.GetTypeInfo()))
             {
                 var values = request.Headers.GetCommaSeparatedValues(headerName);
                 if (values != null)

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

@@ -1962,38 +1962,6 @@ namespace Microsoft.AspNet.Mvc.Core
             return string.Format(CultureInfo.CurrentCulture, GetString("ModelBinderUtil_ModelTypeIsWrong"), p0, p1);
         }
 
-        /// <summary>
-        /// The value '{0}' is not valid for {1}.
-        /// </summary>
-        internal static string ModelBinderUtil_ValueInvalid
-        {
-            get { return GetString("ModelBinderUtil_ValueInvalid"); }
-        }
-
-        /// <summary>
-        /// The value '{0}' is not valid for {1}.
-        /// </summary>
-        internal static string FormatModelBinderUtil_ValueInvalid(object p0, object p1)
-        {
-            return string.Format(CultureInfo.CurrentCulture, GetString("ModelBinderUtil_ValueInvalid"), p0, p1);
-        }
-
-        /// <summary>
-        /// The supplied value is invalid for {0}.
-        /// </summary>
-        internal static string ModelBinderUtil_ValueInvalidGeneric
-        {
-            get { return GetString("ModelBinderUtil_ValueInvalidGeneric"); }
-        }
-
-        /// <summary>
-        /// The supplied value is invalid for {0}.
-        /// </summary>
-        internal static string FormatModelBinderUtil_ValueInvalidGeneric(object p0)
-        {
-            return string.Format(CultureInfo.CurrentCulture, GetString("ModelBinderUtil_ValueInvalidGeneric"), p0);
-        }
-
         /// <summary>
         /// A value for the '{0}' property was not provided.
         /// </summary>

src/Microsoft.AspNet.Mvc.Core/Resources.resx

@@ -493,12 +493,6 @@
   <data name="ModelBinderUtil_ModelTypeIsWrong" xml:space="preserve">
     <value>The binding context has a ModelType of '{0}', but this binder can only operate on models of type '{1}'.</value>
   </data>
-  <data name="ModelBinderUtil_ValueInvalid" xml:space="preserve">
-    <value>The value '{0}' is not valid for {1}.</value>
-  </data>
-  <data name="ModelBinderUtil_ValueInvalidGeneric" xml:space="preserve">
-    <value>The supplied value is invalid for {0}.</value>
-  </data>
   <data name="ModelBinding_MissingBindRequiredMember" xml:space="preserve">
     <value>A value for the '{0}' property was not provided.</value>
   </data>

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

@@ -1898,102 +1898,6 @@ namespace Microsoft.AspNet.Mvc.Extensions
             return GetString("KeyValuePair_BothKeyAndValueMustBePresent");
         }
 
-        /// <summary>
-        /// The binding context has a null Model, but this binder requires a non-null model of type '{0}'.
-        /// </summary>
-        internal static string ModelBinderUtil_ModelCannotBeNull
-        {
-            get { return GetString("ModelBinderUtil_ModelCannotBeNull"); }
-        }
-
-        /// <summary>
-        /// The binding context has a null Model, but this binder requires a non-null model of type '{0}'.
-        /// </summary>
-        internal static string FormatModelBinderUtil_ModelCannotBeNull(object p0)
-        {
-            return string.Format(CultureInfo.CurrentCulture, GetString("ModelBinderUtil_ModelCannotBeNull"), p0);
-        }
-
-        /// <summary>
-        /// The binding context has a Model of type '{0}', but this binder can only operate on models of type '{1}'.
-        /// </summary>
-        internal static string ModelBinderUtil_ModelInstanceIsWrong
-        {
-            get { return GetString("ModelBinderUtil_ModelInstanceIsWrong"); }
-        }
-
-        /// <summary>
-        /// The binding context has a Model of type '{0}', but this binder can only operate on models of type '{1}'.
-        /// </summary>
-        internal static string FormatModelBinderUtil_ModelInstanceIsWrong(object p0, object p1)
-        {
-            return string.Format(CultureInfo.CurrentCulture, GetString("ModelBinderUtil_ModelInstanceIsWrong"), p0, p1);
-        }
-
-        /// <summary>
-        /// The binding context cannot have a null ModelMetadata.
-        /// </summary>
-        internal static string ModelBinderUtil_ModelMetadataCannotBeNull
-        {
-            get { return GetString("ModelBinderUtil_ModelMetadataCannotBeNull"); }
-        }
-
-        /// <summary>
-        /// The binding context cannot have a null ModelMetadata.
-        /// </summary>
-        internal static string FormatModelBinderUtil_ModelMetadataCannotBeNull()
-        {
-            return GetString("ModelBinderUtil_ModelMetadataCannotBeNull");
-        }
-
-        /// <summary>
-        /// The binding context has a ModelType of '{0}', but this binder can only operate on models of type '{1}'.
-        /// </summary>
-        internal static string ModelBinderUtil_ModelTypeIsWrong
-        {
-            get { return GetString("ModelBinderUtil_ModelTypeIsWrong"); }
-        }
-
-        /// <summary>
-        /// The binding context has a ModelType of '{0}', but this binder can only operate on models of type '{1}'.
-        /// </summary>
-        internal static string FormatModelBinderUtil_ModelTypeIsWrong(object p0, object p1)
-        {
-            return string.Format(CultureInfo.CurrentCulture, GetString("ModelBinderUtil_ModelTypeIsWrong"), p0, p1);
-        }
-
-        /// <summary>
-        /// The value '{0}' is not valid for {1}.
-        /// </summary>
-        internal static string ModelBinderUtil_ValueInvalid
-        {
-            get { return GetString("ModelBinderUtil_ValueInvalid"); }
-        }
-
-        /// <summary>
-        /// The value '{0}' is not valid for {1}.
-        /// </summary>
-        internal static string FormatModelBinderUtil_ValueInvalid(object p0, object p1)
-        {
-            return string.Format(CultureInfo.CurrentCulture, GetString("ModelBinderUtil_ValueInvalid"), p0, p1);
-        }
-
-        /// <summary>
-        /// The supplied value is invalid for {0}.
-        /// </summary>
-        internal static string ModelBinderUtil_ValueInvalidGeneric
-        {
-            get { return GetString("ModelBinderUtil_ValueInvalidGeneric"); }
-        }
-
-        /// <summary>
-        /// The supplied value is invalid for {0}.
-        /// </summary>
-        internal static string FormatModelBinderUtil_ValueInvalidGeneric(object p0)
-        {
-            return string.Format(CultureInfo.CurrentCulture, GetString("ModelBinderUtil_ValueInvalidGeneric"), p0);
-        }
-
         /// <summary>
         /// The '{0}' property is required.
         /// </summary>

src/Microsoft.AspNet.Mvc.Extensions/Resources.resx

@@ -481,24 +481,6 @@
   <data name="KeyValuePair_BothKeyAndValueMustBePresent" xml:space="preserve">
     <value>A value is required.</value>
   </data>
-  <data name="ModelBinderUtil_ModelCannotBeNull" xml:space="preserve">
-    <value>The binding context has a null Model, but this binder requires a non-null model of type '{0}'.</value>
-  </data>
-  <data name="ModelBinderUtil_ModelInstanceIsWrong" xml:space="preserve">
-    <value>The binding context has a Model of type '{0}', but this binder can only operate on models of type '{1}'.</value>
-  </data>
-  <data name="ModelBinderUtil_ModelMetadataCannotBeNull" xml:space="preserve">
-    <value>The binding context cannot have a null ModelMetadata.</value>
-  </data>
-  <data name="ModelBinderUtil_ModelTypeIsWrong" xml:space="preserve">
-    <value>The binding context has a ModelType of '{0}', but this binder can only operate on models of type '{1}'.</value>
-  </data>
-  <data name="ModelBinderUtil_ValueInvalid" xml:space="preserve">
-    <value>The value '{0}' is not valid for {1}.</value>
-  </data>
-  <data name="ModelBinderUtil_ValueInvalidGeneric" xml:space="preserve">
-    <value>The supplied value is invalid for {0}.</value>
-  </data>
   <data name="ModelBinding_MissingRequiredMember" xml:space="preserve">
     <value>The '{0}' property is required.</value>
   </data>

test/Microsoft.AspNet.Mvc.Core.Test/ModelBinding/BodyModelBinderTests.cs

@@ -77,10 +77,15 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
 
             // Returns true because it understands the metadata type.
             Assert.NotNull(binderResult);
+            Assert.True(binderResult.IsFatalError);
             Assert.False(binderResult.IsModelSet);
             Assert.Null(binderResult.ValidationNode);
             Assert.Null(binderResult.Model);
-            Assert.True(bindingContext.ModelState.ContainsKey("someName"));
+
+            // Key is empty because this was a top-level binding.
+            var entry = Assert.Single(bindingContext.ModelState);
+            Assert.Equal(string.Empty, entry.Key);
+            Assert.Single(entry.Value.Errors);
         }
 
         [Fact]
@@ -99,6 +104,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
 
             // Assert
             Assert.NotNull(binderResult);
+            Assert.True(binderResult.IsFatalError);
             Assert.False(binderResult.IsModelSet);
             Assert.Null(binderResult.ValidationNode);
         }
@@ -167,11 +173,15 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
 
             // Returns true because it understands the metadata type.
             Assert.NotNull(binderResult);
+            Assert.True(binderResult.IsFatalError);
             Assert.False(binderResult.IsModelSet);
             Assert.Null(binderResult.ValidationNode);
             Assert.Null(binderResult.Model);
-            Assert.True(bindingContext.ModelState.ContainsKey("someName"));
+
-            var errorMessage = bindingContext.ModelState["someName"].Errors[0].Exception.Message;
+            // Key is empty because this was a top-level binding.
+            var entry = Assert.Single(bindingContext.ModelState);
+            Assert.Equal(string.Empty, entry.Key);
+            var errorMessage = Assert.Single(entry.Value.Errors).Exception.Message;
             Assert.Equal("Your input is bad!", errorMessage);
         }
 
@@ -198,13 +208,17 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
 
             // Assert
 
-            // Returns true because it understands the metadata type.
+            // Returns non-null result because it understands the metadata type.
             Assert.NotNull(binderResult);
+            Assert.True(binderResult.IsFatalError);
             Assert.False(binderResult.IsModelSet);
             Assert.Null(binderResult.Model);
             Assert.Null(binderResult.ValidationNode);
-            Assert.True(bindingContext.ModelState.ContainsKey("someName"));
+
-            var errorMessage = bindingContext.ModelState["someName"].Errors[0].ErrorMessage;
+            // Key is empty because this was a top-level binding.
+            var entry = Assert.Single(bindingContext.ModelState);
+            Assert.Equal(string.Empty, entry.Key);
+            var errorMessage = Assert.Single(entry.Value.Errors).ErrorMessage;
             Assert.Equal("Unsupported content type 'text/xyz'.", errorMessage);
         }
 

test/Microsoft.AspNet.Mvc.FunctionalTests/InputObjectValidationTests.cs

@@ -65,7 +65,7 @@ namespace Microsoft.AspNet.Mvc.FunctionalTests
             // Act
             var response = await client.PostAsync("http://localhost/Validation/Index", content);
 
-            //Assert
+            // Assert
             Assert.Equal(HttpStatusCode.OK, response.StatusCode);
             Assert.Equal("User has been registerd : " + sampleName,
                 await response.Content.ReadAsStringAsync());
@@ -89,7 +89,7 @@ namespace Microsoft.AspNet.Mvc.FunctionalTests
             // Act
             var response = await client.PostAsync("http://localhost/Validation/Index", content);
 
-            //Assert
+            // Assert
             Assert.Equal(HttpStatusCode.OK, response.StatusCode);
             Assert.Equal("The field Id must be between 1 and 2000.," +
                 "The field Name must be a string or array type with a minimum length of '5'.," +
@@ -109,7 +109,7 @@ namespace Microsoft.AspNet.Mvc.FunctionalTests
             // Act
             var response = await client.PostAsync("http://localhost/Validation/GetDeveloperName", content);
 
-            //Assert
+            // Assert
             Assert.Equal(HttpStatusCode.OK, response.StatusCode);
             Assert.Equal("No model validation for developer, even though developer.Name is empty.",
                          await response.Content.ReadAsStringAsync());
@@ -131,25 +131,25 @@ namespace Microsoft.AspNet.Mvc.FunctionalTests
             // Act
             var response = await client.PostAsync("http://localhost/Validation/CreateProject", content);
 
-            //Assert
+            // Assert
             Assert.Equal(StatusCodes.Status400BadRequest, (int)response.StatusCode);
 
             var responseContent = await response.Content.ReadAsStringAsync();
-            var responseObject = JsonConvert.DeserializeObject<Dictionary<string, ErrorCollection>>(responseContent);
+            var responseObject = JsonConvert.DeserializeObject<Dictionary<string, string[]>>(responseContent);
-            var errorCollection = Assert.Single(responseObject, modelState => modelState.Value.Errors.Any());
+            var errorKeyValuePair = Assert.Single(responseObject, keyValuePair => keyValuePair.Value.Length > 0);
-            var error = Assert.Single(errorCollection.Value.Errors);
+            var errorMessage = Assert.Single(errorKeyValuePair.Value);
-            Assert.Equal(expectedModelStateErrorMessage, error.ErrorMessage);
+            Assert.Equal(expectedModelStateErrorMessage, errorMessage);
 
             // verifies that the excluded type is not validated
-            Assert.NotEqual(shouldNotContainMessage, error.ErrorMessage);
+            Assert.NotEqual(shouldNotContainMessage, errorMessage);
         }
 
         [Theory]
         [MemberData(nameof(SimpleTypePropertiesModelRequestData))]
-        public async Task ShallowValidation_HappensOnExlcuded_SimpleTypeProperties(
+        public async Task ShallowValidation_HappensOnExcluded_SimpleTypeProperties(
-                                                            string requestContent,
+            string requestContent,
-                                                            int expectedStatusCode,
+            int expectedStatusCode,
-                                                            string expectedModelStateErrorMessage)
+            string expectedModelStateErrorMessage)
         {
             // Arrange
             var server = TestHelper.CreateServer(_app, SiteName, _configureServices);
@@ -157,17 +157,18 @@ namespace Microsoft.AspNet.Mvc.FunctionalTests
             var content = new StringContent(requestContent, Encoding.UTF8, "application/json");
 
             // Act
-            var response = await client.PostAsync("http://localhost/Validation/CreateSimpleTypePropertiesModel",
+            var response = await client.PostAsync(
-                                                  content);
+                "http://localhost/Validation/CreateSimpleTypePropertiesModel",
+                content);
 
-            //Assert
+            // Assert
             Assert.Equal(expectedStatusCode, (int)response.StatusCode);
 
             var responseContent = await response.Content.ReadAsStringAsync();
-            var responseObject = JsonConvert.DeserializeObject<Dictionary<string, ErrorCollection>>(responseContent);
+            var responseObject = JsonConvert.DeserializeObject<Dictionary<string, string[]>>(responseContent);
-            var errorCollection = Assert.Single(responseObject, modelState => modelState.Value.Errors.Any());
+            var errorKeyValuePair = Assert.Single(responseObject, keyValuePair => keyValuePair.Value.Length > 0);
-            var error = Assert.Single(errorCollection.Value.Errors);
+            var errorMessage = Assert.Single(errorKeyValuePair.Value);
-            Assert.Equal(expectedModelStateErrorMessage, error.ErrorMessage);
+            Assert.Equal(expectedModelStateErrorMessage, errorMessage);
         }
 
         [Fact]
@@ -183,27 +184,9 @@ namespace Microsoft.AspNet.Mvc.FunctionalTests
             // Act
             var response = await client.PostAsync("http://localhost/Validation/GetDeveloperAlias", content);
 
-            //Assert
+            // Assert
             Assert.Equal(HttpStatusCode.OK, response.StatusCode);
             Assert.Equal("xyz", await response.Content.ReadAsStringAsync());
         }
-
-        private class ErrorCollection
-        {
-            public IEnumerable<Error> Errors
-            {
-                get;
-                set;
-            }
-        }
-
-        private class Error
-        {
-            public string ErrorMessage
-            {
-                get;
-                set;
-            }
-        }
     }
 }

test/Microsoft.AspNet.Mvc.FunctionalTests/ModelBindingTest.cs

@@ -11,7 +11,6 @@ using System.Reflection;
 using System.Text;
 using System.Threading.Tasks;
 using Microsoft.AspNet.Builder;
-using Microsoft.AspNet.Mvc.ModelBinding;
 using Microsoft.Framework.DependencyInjection;
 using ModelBindingWebSite.Models;
 using ModelBindingWebSite.ViewModels;
@@ -39,9 +38,7 @@ namespace Microsoft.AspNet.Mvc.FunctionalTests
             var response = await client.GetStringAsync("http://localhost/Validation/DoNotValidateParameter");
 
             // Assert
-            var modelState = JsonConvert.DeserializeObject<ModelStateDictionary>(response);
+            Assert.Equal("true", response);
-            Assert.Empty(modelState);
-            Assert.True(modelState.IsValid);
         }
 
         [Fact]
@@ -52,13 +49,10 @@ namespace Microsoft.AspNet.Mvc.FunctionalTests
             var client = server.CreateClient();
 
             // Act
-            var response = await client.GetAsync(
+            var response = await client.GetStringAsync("http://localhost/Validation/AvoidRecursive?Name=selfish");
-                "http://localhost/Validation/AvoidRecursive?Name=selfish");
 
             // Assert
-            var stringValue = await response.Content.ReadAsStringAsync();
+            Assert.Equal("true", response);
-            var json = JsonConvert.DeserializeObject<ModelStateDictionary>(stringValue);
-            Assert.True(json.IsValid);
         }
 
         [Theory]

test/Microsoft.AspNet.Mvc.FunctionalTests/XmlDataContractSerializerInputFormatterTest.cs

@@ -49,7 +49,7 @@ namespace Microsoft.AspNet.Mvc.FunctionalTests
             var data = await response.Content.ReadAsStringAsync();
             Assert.Contains(
                 string.Format(
-                    "dummyObject:There was an error deserializing the object of type {0}",
+                    ":There was an error deserializing the object of type {0}.",
                     typeof(DummyClass).FullName),
                 data);
         }

test/Microsoft.AspNet.Mvc.FunctionalTests/XmlSerializerInputFormatterTests.cs

@@ -53,7 +53,7 @@ namespace Microsoft.AspNet.Mvc.FunctionalTests
             // Assert
             Assert.Equal(HttpStatusCode.BadRequest, response.StatusCode);
             var data = await response.Content.ReadAsStringAsync();
-            Assert.Contains("dummyObject:There is an error in XML document", data);
+            Assert.Contains(":There is an error in XML document", data);
         }
     }
 }

test/WebSites/FormatterWebSite/Controllers/InputFormatterController.cs

@@ -14,8 +14,10 @@ namespace FormatterWebSite.Controllers
         {
             if (!ActionContext.ModelState.IsValid)
             {
-                var parameterBindingErrors = ActionContext.ModelState["dummy"].Errors;
+                // Body model binder normally reports errors for parameters using the empty name.
-                if (parameterBindingErrors.Count != 0)
+                var parameterBindingErrors = ActionContext.ModelState["dummy"]?.Errors ??
+                    ActionContext.ModelState[string.Empty]?.Errors;
+                if (parameterBindingErrors != null && parameterBindingErrors.Count != 0)
                 {
                     return new ErrorInfo
                     {

test/WebSites/FormatterWebSite/Controllers/ValidationController.cs

@@ -2,8 +2,6 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.ComponentModel.DataAnnotations;
-using System.Threading.Tasks;
 using Microsoft.AspNet.Mvc;
 
 namespace FormatterWebSite
@@ -59,7 +57,7 @@ namespace FormatterWebSite
         // 'Developer' type is excluded but the shallow validation on the
         // property Developers should happen
         [ModelStateValidationFilter]
-        public IActionResult CreateProject([FromBody]Project project)
+        public IActionResult CreateProject([FromBody] Project project)
         {
             return Json(project);
         }

test/WebSites/FormatterWebSite/Filters/ModelStateValidationFilterAttribute.cs

@@ -2,7 +2,6 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using Microsoft.AspNet.Mvc;
-using Microsoft.AspNet.WebUtilities;
 
 namespace FormatterWebSite
 {
@@ -12,10 +11,7 @@ namespace FormatterWebSite
         {
             if (!context.ModelState.IsValid)
             {
-                context.Result = new ObjectResult(context.ModelState)
+                context.Result = new BadRequestObjectResult(context.ModelState);
-                {
-                    StatusCode = StatusCodes.Status400BadRequest
-                };
             }
         }
     }

test/WebSites/FormatterWebSite/ValidateBodyParameterAttribute.cs

@@ -19,8 +19,10 @@ namespace FormatterWebSite
                                               parameter.BindingInfo?.BindingSource));
                 if (bodyParameter != null)
                 {
-                    var parameterBindingErrors = context.ModelState[bodyParameter.Name].Errors;
+                    // Body model binder normally reports errors for parameters using the empty name.
-                    if (parameterBindingErrors.Count != 0)
+                    var parameterBindingErrors = context.ModelState[bodyParameter.Name]?.Errors ??
+                        context.ModelState[string.Empty]?.Errors;
+                    if (parameterBindingErrors != null && parameterBindingErrors.Count != 0)
                     {
                         var errorInfo = new ErrorInfo
                         {

test/WebSites/ModelBindingWebSite/Controllers/ValidationController.cs

@@ -1,10 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-using System.Collections.Generic;
 using Microsoft.AspNet.Mvc;
-using Microsoft.AspNet.Mvc.ModelBinding;
-using ModelBindingWebSite.Models;
 
 namespace ModelBindingWebSite.Controllers
 {
@@ -16,61 +13,19 @@ namespace ModelBindingWebSite.Controllers
 
         public object AvoidRecursive(SelfishPerson selfishPerson)
         {
-            return new SerializableModelStateDictionary(ModelState);
+            return ModelState.IsValid;
         }
 
         public object DoNotValidateParameter([FromServices] ITestService service)
         {
-            return ModelState;
+            return ModelState.IsValid;
         }
     }
 
-    public class SerializableModelStateDictionary : Dictionary<string, Entry>
-    {
-        public bool IsValid { get; set; }
-
-        public int ErrorCount { get; set; }
-
-        public SerializableModelStateDictionary(ModelStateDictionary modelState)
-        {
-            var errorCount = 0;
-            foreach (var keyModelStatePair in modelState)
-            {
-                var key = keyModelStatePair.Key;
-                var value = keyModelStatePair.Value;
-                errorCount += value.Errors.Count;
-                var entry = new Entry()
-                {
-                    Errors = value.Errors,
-                    RawValue = value.Value.RawValue,
-                    AttemptedValue = value.Value.AttemptedValue,
-                    ValidationState = value.ValidationState
-                };
-
-                Add(key, entry);
-            }
-
-            IsValid = modelState.IsValid;
-            ErrorCount = errorCount;
-        }
-    }
-
-    public class Entry
-    {
-        public ModelValidationState ValidationState { get; set; }
-
-        public ModelErrorCollection Errors { get; set; }
-
-        public object RawValue { get; set; }
-
-        public string AttemptedValue { get; set; }
-
-    }
-
-
     public class SelfishPerson
     {
         public string Name { get; set; }
+
         public SelfishPerson MySelf { get { return this; } }
     }
 }