Clean up `ModelBindingResult` constructor calls and related comments

- use named parameters more often
 - add more comments about returned `ModelBindingResult`
 - clean up `ModelBindingResult` doc comments
 - cleanup `using`s

Nits:
- cleanup trailing whitespace
- change `retVal` -> `result` in `KeyValuePairModelBinderTest`

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

@@ -6,8 +6,6 @@ using System.Linq;
 using System.Reflection;
 using System.Threading.Tasks;
 using Microsoft.AspNet.Mvc.Core;
-using Microsoft.AspNet.Mvc.ModelBinding;
-using Microsoft.Framework.DependencyInjection;
 using Microsoft.Framework.Internal;
 
 namespace Microsoft.AspNet.Mvc.ModelBinding
@@ -57,6 +55,9 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
                 var unsupportedContentType = Resources.FormatUnsupportedContentType(
                     bindingContext.OperationBindingContext.HttpContext.Request.ContentType);
                 bindingContext.ModelState.AddModelError(bindingContext.ModelName, unsupportedContentType);
+
+                // This model binder is the only handler for the Body binding source.
+                // Always tell the model binding system to skip other model binders i.e. return non-null.
                 return new ModelBindingResult(model: null, key: bindingContext.ModelName, isModelSet: false);
             }
 
@@ -69,9 +70,13 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             {
                 model = GetDefaultValueForType(bindingContext.ModelType);
                 bindingContext.ModelState.AddModelError(bindingContext.ModelName, ex);
+
+                // This model binder is the only handler for the Body binding source.
+                // Always tell the model binding system to skip other model binders i.e. return non-null.
                 return new ModelBindingResult(model: null, key: bindingContext.ModelName, isModelSet: false);
             }
 
+            // Success
             // key is empty to ensure that the model name is not used as a prefix for validation.
             return new ModelBindingResult(model, key: string.Empty, isModelSet: true);
         }

src/Microsoft.AspNet.Mvc.Core/ModelBinders/ServicesModelBinder.cs

@@ -26,7 +26,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
         {
             var requestServices = bindingContext.OperationBindingContext.HttpContext.RequestServices;
             var model = requestServices.GetRequiredService(bindingContext.ModelType);
-            return Task.FromResult(new ModelBindingResult(model, bindingContext.ModelName, true));
+            return Task.FromResult(new ModelBindingResult(model, bindingContext.ModelName, isModelSet: true));
         }
     }
 }

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

@@ -33,7 +33,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             var requestServices = bindingContext.OperationBindingContext.HttpContext.RequestServices;
             var createFactory = _typeActivatorCache.GetOrAdd(bindingContext.BinderType, _createFactory);
             var instance = createFactory(requestServices, arguments: null);
-            
+
             var modelBinder = instance as IModelBinder;
             if (modelBinder == null)
             {
@@ -54,12 +54,12 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
 
             var result = await modelBinder.BindModelAsync(bindingContext);
 
-            var modelBindingResult = result != null ? 
+            var modelBindingResult = result != null ?
                 new ModelBindingResult(result.Model, result.Key, result.IsModelSet) :
-                new ModelBindingResult(null, bindingContext.ModelName, false);
+                new ModelBindingResult(model: null, key: bindingContext.ModelName, isModelSet: false);
 
-            // return a non null modelbinding result here, because this binder will handle all cases where the
-            //  model binder is specified by metadata.
+            // A model binder was specified by metadata and this binder handles all such cases.
+            // Always tell the model binding system to skip other model binders i.e. return non-null.
             return modelBindingResult;
         }
     }

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

@@ -59,6 +59,10 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
         /// <returns>
         /// A <see cref="Task"/> which will complete when model binding has completed.
         /// </returns>
+        /// <remarks>
+        /// Other model binders will never run if this method is called. Return <c>null</c> to skip other model binders
+        /// but allow higher-level handling e.g. falling back to empty prefix.
+        /// </remarks>
         protected abstract Task<ModelBindingResult> BindModelCoreAsync([NotNull] ModelBindingContext bindingContext);
 
         /// <inheritdoc />
@@ -74,13 +78,13 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
 
             var result = await BindModelCoreAsync(context);
 
-            var modelBindingResult = 
-                result != null ? 
+            var modelBindingResult =
+                result != null ?
                     new ModelBindingResult(result.Model, result.Key, result.IsModelSet) :
-                    new ModelBindingResult(null, context.ModelName, false);
+                    new ModelBindingResult(model: null, key: context.ModelName, isModelSet: false);
 
-            // Prevent other model binders from running because this model binder is the only handler for
-            // its binding source.
+            // 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.
             return modelBindingResult;
         }
     }

src/Microsoft.AspNet.Mvc.ModelBinding/Binders/ByteArrayModelBinder.cs

@@ -3,7 +3,6 @@
 
 using System;
 using System.Threading.Tasks;
-using Microsoft.AspNet.Mvc.ModelBinding.Internal;
 using Microsoft.Framework.Internal;
 
 namespace Microsoft.AspNet.Mvc.ModelBinding
@@ -40,13 +39,15 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             try
             {
                 var model = Convert.FromBase64String(value);
-                return new ModelBindingResult(model, bindingContext.ModelName, true);
+                return new ModelBindingResult(model, bindingContext.ModelName, isModelSet: true);
             }
             catch (Exception ex)
             {
                 bindingContext.ModelState.TryAddModelError(bindingContext.ModelName, ex);
             }
 
+            // Matched the type (byte[]) only this binder supports.
+            // Always tell the model binding system to skip other model binders i.e. return non-null.
             return new ModelBindingResult(model: null, key: bindingContext.ModelName, isModelSet: false);
         }
     }

src/Microsoft.AspNet.Mvc.ModelBinding/Binders/CancellationTokenModelBinder.cs

@@ -17,7 +17,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             if (bindingContext.ModelType == typeof(CancellationToken))
             {
                 var model = bindingContext.OperationBindingContext.HttpContext.RequestAborted;
-                return Task.FromResult(new ModelBindingResult(model, bindingContext.ModelName, true));
+                return Task.FromResult(new ModelBindingResult(model, bindingContext.ModelName, isModelSet: true));
             }
 
             return Task.FromResult<ModelBindingResult>(null);

src/Microsoft.AspNet.Mvc.ModelBinding/Binders/CollectionModelBinder.cs

@@ -28,7 +28,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
                     BindComplexCollection(bindingContext);
             var boundCollection = await bindCollectionTask;
             var model = GetModel(boundCollection);
-            return new ModelBindingResult(model, bindingContext.ModelName, true);
+            return new ModelBindingResult(model, bindingContext.ModelName, isModelSet: true);
         }
 
         // Used when the ValueProvider contains the collection to be bound as a single element, e.g. the raw value

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

@@ -5,7 +5,6 @@ using System;
 using System.Collections.Generic;
 using System.Runtime.CompilerServices;
 using System.Threading.Tasks;
-using Microsoft.Framework.DependencyInjection;
 using Microsoft.Framework.Internal;
 
 namespace Microsoft.AspNet.Mvc.ModelBinding
@@ -34,14 +33,14 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
 
         public virtual async Task<ModelBindingResult> BindModelAsync([NotNull] ModelBindingContext bindingContext)
         {
-            var newBindingContext = CreateNewBindingContext(bindingContext,
-                                                            bindingContext.ModelName);
-
+            var newBindingContext = CreateNewBindingContext(bindingContext, bindingContext.ModelName);
             var modelBindingResult = await TryBind(newBindingContext);
-            if (modelBindingResult == null && !string.IsNullOrEmpty(bindingContext.ModelName)
-                && bindingContext.FallbackToEmptyPrefix)
+
+            if (modelBindingResult == null &&
+                bindingContext.FallbackToEmptyPrefix &&
+                !string.IsNullOrEmpty(bindingContext.ModelName))
             {
-                // fallback to empty prefix?
+                // Fall back to empty prefix.
                 newBindingContext = CreateNewBindingContext(bindingContext,
                                                             modelName: string.Empty);
                 modelBindingResult = await TryBind(newBindingContext);
@@ -75,13 +74,14 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
                     // {
                     // }
                     //
-                    // In this case, for the model parameter the key would be SimpleType instead of model.SimpleType. 
+                    // In this case, for the model parameter the key would be SimpleType instead of model.SimpleType.
                     // (i.e here the prefix for the model key is empty).
                     // For the id parameter the key would be id.
                     return modelBindingResult;
                 }
             }
 
+            // Fall through to update the ModelBindingResult's key.
             return new ModelBindingResult(
                 modelBindingResult.Model,
                 bindingContext.ModelName,

src/Microsoft.AspNet.Mvc.ModelBinding/Binders/FormCollectionModelBinder.cs

@@ -46,7 +46,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
                 model = new FormCollection(new Dictionary<string, string[]>());
             }
 
-            return new ModelBindingResult(model, bindingContext.ModelName, true);
+            return new ModelBindingResult(model, bindingContext.ModelName, isModelSet: true);
         }
     }
 }

src/Microsoft.AspNet.Mvc.ModelBinding/Binders/FormFileModelBinder.cs

@@ -25,14 +25,14 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             {
                 var postedFiles = await GetFormFilesAsync(bindingContext);
                 var value = postedFiles.FirstOrDefault();
-                return new ModelBindingResult(value, bindingContext.ModelName, value != null);
+                return new ModelBindingResult(value, bindingContext.ModelName, isModelSet: value != null);
             }
             else if (typeof(IEnumerable<IFormFile>).GetTypeInfo().IsAssignableFrom(
                     bindingContext.ModelType.GetTypeInfo()))
             {
                 var postedFiles = await GetFormFilesAsync(bindingContext);
                 var value = ModelBindingHelper.ConvertValuesToCollectionType(bindingContext.ModelType, postedFiles);
-                return new ModelBindingResult(value, bindingContext.ModelName, value != null);
+                return new ModelBindingResult(value, bindingContext.ModelName, isModelSet: value != null);
             }
 
             return null;

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

@@ -22,10 +22,10 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
 
                 var modelBindingResult = result != null ?
                     new ModelBindingResult(result.Model, result.Key, result.IsModelSet) :
-                    new ModelBindingResult(null, bindingContext.ModelName, false);
+                    new ModelBindingResult(model: null, key: bindingContext.ModelName, isModelSet: false);
 
-                // Was able to resolve a binder type, hence we should tell the model binding system to return
-                // true so that none of the other model binders participate.
+                // Were able to resolve a binder type.
+                // Always tell the model binding system to skip other model binders i.e. return non-null.
                 return modelBindingResult;
             }
 

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

@@ -52,7 +52,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
                 }
             }
 
-            return Task.FromResult(new ModelBindingResult(model, bindingContext.ModelName, model != null));
+            return Task.FromResult(new ModelBindingResult(model, bindingContext.ModelName, isModelSet: model != null));
         }
     }
 }

src/Microsoft.AspNet.Mvc.ModelBinding/Binders/KeyValuePairModelBinder.cs

@@ -2,7 +2,6 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System.Collections.Generic;
-using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.AspNet.Mvc.ModelBinding.Internal;
 
@@ -25,6 +24,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
                     ModelBindingHelper.CastOrDefault<TKey>(keyResult.Model),
                     ModelBindingHelper.CastOrDefault<TValue>(valueResult.Model));
 
+                // Success
                 return new ModelBindingResult(model, bindingContext.ModelName, isModelSet: true);
             }
             else if (!keyResult.IsModelSet && valueResult.IsModelSet)
@@ -32,6 +32,9 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
                 bindingContext.ModelState.TryAddModelError(
                     keyResult.Key,
                     Resources.KeyValuePair_BothKeyAndValueMustBePresent);
+
+                // Were able to get some data for this model.
+                // Always tell the model binding system to skip other model binders i.e. return non-null.
                 return new ModelBindingResult(model: null, key: bindingContext.ModelName, isModelSet: false);
             }
             else if (keyResult.IsModelSet && !valueResult.IsModelSet)
@@ -39,10 +42,15 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
                 bindingContext.ModelState.TryAddModelError(
                     valueResult.Key,
                     Resources.KeyValuePair_BothKeyAndValueMustBePresent);
+
+                // Were able to get some data for this model.
+                // Always tell the model binding system to skip other model binders i.e. return non-null.
                 return new ModelBindingResult(model: null, key: bindingContext.ModelName, isModelSet: false);
             }
             else
             {
+                // Caller (GenericModelBinder) was able to resolve a binder type and will create a ModelBindingResult
+                // that exits current ModelBinding loop.
                 return null;
             }
         }
@@ -58,16 +66,16 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
                 parentBindingContext,
                 propertyModelName,
                 propertyModelMetadata);
-
             propertyBindingContext.BinderModelName = propertyModelMetadata.BinderModelName;
 
-            var modelBindingResult = 
-                await propertyBindingContext.OperationBindingContext.ModelBinder.BindModelAsync(propertyBindingContext);
+            var modelBindingResult = await propertyBindingContext.OperationBindingContext.ModelBinder.BindModelAsync(
+                propertyBindingContext);
             if (modelBindingResult != null)
             {
                 return modelBindingResult;
             }
 
+            // Always return a ModelBindingResult to avoid an NRE in BindModelAsync.
             return new ModelBindingResult(model: default(TModel), key: propertyModelName, isModelSet: false);
         }
     }

src/Microsoft.AspNet.Mvc.ModelBinding/Binders/MutableObjectModelBinder.cs

@@ -40,8 +40,8 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             // post-processing, e.g. property setters and hooking up validation
             ProcessDto(bindingContext, (ComplexModelDto)result.Model);
             return new ModelBindingResult(
-                bindingContext.Model, 
-                bindingContext.ModelName, 
+                bindingContext.Model,
+                bindingContext.ModelName,
                 isModelSet: true);
         }
 
@@ -53,6 +53,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
         internal async Task<bool> CanCreateModel(MutableObjectBinderContext context)
         {
             var bindingContext = context.ModelBindingContext;
+
             var isTopLevelObject = bindingContext.ModelMetadata.ContainerType == null;
             var hasExplicitAlias = bindingContext.BinderModelName != null;
 
@@ -117,7 +118,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             // However, because a property might specify a custom binding source ([FromForm]), it's not correct
             // for us to just try bindingContext.ValueProvider.ContainsPrefixAsync(bindingContext.ModelName),
             // because that may include ALL value providers - that would lead us to mistakenly create the model
-            // when the data is coming from a source we should use (ex: value found in query string, but the 
+            // when the data is coming from a source we should use (ex: value found in query string, but the
             // model has [FromForm]).
             //
             // To do this we need to enumerate the properties, and see which of them provide a binding source
@@ -133,7 +134,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             //      If a property does not have a binding source, then it's fair game for any value provider.
             //
             // If any property meets the above conditions and has a value from valueproviders, then we'll
-            // create the model and try to bind it. OR if ALL properties of the model have a greedy source, 
+            // create the model and try to bind it. OR if ALL properties of the model have a greedy source,
             // then we go ahead and create it.
             //
             var isAnyPropertyEnabledForValueProviderBasedBinding = false;

src/Microsoft.AspNet.Mvc.ModelBinding/Binders/TypeConverterModelBinder.cs

@@ -31,14 +31,16 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             {
                 newModel = valueProviderResult.ConvertTo(bindingContext.ModelType);
                 ModelBindingHelper.ReplaceEmptyStringWithNull(bindingContext.ModelMetadata, ref newModel);
-                return new ModelBindingResult(newModel, bindingContext.ModelName, true);
+                return new ModelBindingResult(newModel, bindingContext.ModelName, isModelSet: true);
             }
             catch (Exception ex)
             {
                 bindingContext.ModelState.TryAddModelError(bindingContext.ModelName, ex);
             }
 
-            return new ModelBindingResult(null, bindingContext.ModelName, false);
+            // Were able to find a converter for the type but conversion failed.
+            // Tell the model binding system to skip other model binders i.e. return non-null.
+            return new ModelBindingResult(model: null, key: bindingContext.ModelName, isModelSet: false);
         }
     }
 }

src/Microsoft.AspNet.Mvc.ModelBinding/Binders/TypeMatchModelBinder.cs

@@ -20,7 +20,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             bindingContext.ModelState.SetModelValue(bindingContext.ModelName, valueProviderResult);
             var model = valueProviderResult.RawValue;
             ModelBindingHelper.ReplaceEmptyStringWithNull(bindingContext.ModelMetadata, ref model);
-            return new ModelBindingResult(model, bindingContext.ModelName, true);
+            return new ModelBindingResult(model, bindingContext.ModelName, isModelSet: true);
         }
 
         internal static async Task<ValueProviderResult> GetCompatibleValueProviderResult(ModelBindingContext context)

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

@@ -23,22 +23,28 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
         }
 
         /// <summary>
-        /// Gets or sets the model associated with this context.
+        /// Gets the model associated with this context.
         /// </summary>
         public object Model { get; }
 
         /// <summary>
-        /// Gets or sets the model name which was used to bind the model.
-        /// 
+        /// <para>
+        /// Gets the model name which was used to bind the model.
+        /// </para>
+        /// <para>
         /// This property can be used during validation to add model state for a bound model.
+        /// </para>
         /// </summary>
         public string Key { get; }
 
         /// <summary>
-        /// Gets or sets a value indicating whether or not the <see cref="Model"/> value has been set.
-        /// 
+        /// <para>
+        /// Gets a value indicating whether or not the <see cref="Model"/> value has been set.
+        /// </para>
+        /// <para>
         /// This property can be used to distinguish between a model binder which does not find a value and
         /// the case where a model binder sets the <c>null</c> value.
+        /// </para>
         /// </summary>
         public bool IsModelSet { get; }
     }

src/Microsoft.AspNet.Mvc.WebApiCompatShim/HttpRequestMessage/HttpRequestMessageModelBinder.cs

@@ -14,7 +14,7 @@ namespace Microsoft.AspNet.Mvc.WebApiCompatShim
             if (bindingContext.ModelType == typeof(HttpRequestMessage))
             {
                 var model = bindingContext.OperationBindingContext.HttpContext.GetHttpRequestMessage();
-                return Task.FromResult(new ModelBindingResult(model, bindingContext.ModelName, true));
+                return Task.FromResult(new ModelBindingResult(model, bindingContext.ModelName, isModelSet: true));
             }
 
             return Task.FromResult<ModelBindingResult>(null);

test/Microsoft.AspNet.Mvc.ModelBinding.Test/Binders/KeyValuePairModelBinderTest.cs

@@ -4,7 +4,6 @@
 #if DNX451
 using System;
 using System.Collections.Generic;
-using System.ComponentModel.DataAnnotations;
 using System.Linq;
 using System.Threading.Tasks;
 using Moq;
@@ -25,11 +24,11 @@ namespace Microsoft.AspNet.Mvc.ModelBinding.Test
             var binder = new KeyValuePairModelBinder<int, string>();
 
             // Act
-            var retVal = await binder.BindModelAsync(bindingContext);
+            var result = await binder.BindModelAsync(bindingContext);
 
             // Assert
-            Assert.NotNull(retVal);
-            Assert.Null(retVal.Model);
+            Assert.NotNull(result);
+            Assert.Null(result.Model);
             Assert.False(bindingContext.ModelState.IsValid);
             Assert.Equal("someName", bindingContext.ModelName);
             var error = Assert.Single(bindingContext.ModelState["someName.Key"].Errors);
@@ -47,11 +46,11 @@ namespace Microsoft.AspNet.Mvc.ModelBinding.Test
             var binder = new KeyValuePairModelBinder<int, string>();
 
             // Act
-            var retVal = await binder.BindModelAsync(bindingContext);
+            var result = await binder.BindModelAsync(bindingContext);
 
             // Assert
-            Assert.NotNull(retVal);
-            Assert.Null(retVal.Model);
+            Assert.NotNull(result);
+            Assert.Null(result.Model);
             Assert.False(bindingContext.ModelState.IsValid);
             Assert.Equal("someName", bindingContext.ModelName);
             Assert.Equal(bindingContext.ModelState["someName.Value"].Errors.First().ErrorMessage, "A value is required.");
@@ -73,10 +72,10 @@ namespace Microsoft.AspNet.Mvc.ModelBinding.Test
             var binder = new KeyValuePairModelBinder<int, string>();
 
             // Act
-            var retVal = await binder.BindModelAsync(bindingContext);
+            var result = await binder.BindModelAsync(bindingContext);
 
             // Assert
-            Assert.Null(retVal);
+            Assert.Null(result);
             Assert.True(bindingContext.ModelState.IsValid);
             Assert.Equal(0, bindingContext.ModelState.ErrorCount);
         }
@@ -92,11 +91,11 @@ namespace Microsoft.AspNet.Mvc.ModelBinding.Test
             var binder = new KeyValuePairModelBinder<int, string>();
 
             // Act
-            var retVal = await binder.BindModelAsync(bindingContext);
+            var result = await binder.BindModelAsync(bindingContext);
 
             // Assert
-            Assert.NotNull(retVal);
-            Assert.Equal(new KeyValuePair<int, string>(42, "some-value"), retVal.Model);
+            Assert.NotNull(result);
+            Assert.Equal(new KeyValuePair<int, string>(42, "some-value"), result.Model);
         }
 
         [Fact]
@@ -107,11 +106,11 @@ namespace Microsoft.AspNet.Mvc.ModelBinding.Test
             var binder = new KeyValuePairModelBinder<int, string>();
 
             // Act
-            var retVal = await binder.TryBindStrongModel<int>(bindingContext, "key");
+            var result = await binder.TryBindStrongModel<int>(bindingContext, "key");
 
             // Assert
-            Assert.True(retVal.IsModelSet);
-            Assert.Equal(42, retVal.Model);
+            Assert.True(result.IsModelSet);
+            Assert.Equal(42, result.Model);
             Assert.Empty(bindingContext.ModelState);
         }
 
@@ -133,11 +132,11 @@ namespace Microsoft.AspNet.Mvc.ModelBinding.Test
             var binder = new KeyValuePairModelBinder<int, string>();
 
             // Act
-            var retVal = await binder.TryBindStrongModel<int>(bindingContext, "key");
+            var result = await binder.TryBindStrongModel<int>(bindingContext, "key");
 
             // Assert
-            Assert.True(retVal.IsModelSet);
-            Assert.Null(retVal.Model);
+            Assert.True(result.IsModelSet);
+            Assert.Null(result.Model);
             Assert.Empty(bindingContext.ModelState);
         }
 

test/Microsoft.AspNet.Mvc.ModelBinding.Test/Binders/MutableObjectModelBinderTest.cs

@@ -7,7 +7,6 @@ using System.Collections.Generic;
 using System.ComponentModel;
 using System.ComponentModel.DataAnnotations;
 using System.Linq;
-using System.Reflection;
 using System.Threading.Tasks;
 using Microsoft.AspNet.Http.Core;
 using Microsoft.AspNet.Testing;
@@ -106,17 +105,15 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
         [Fact]
         public async Task CanCreateModel_ReturnsFalse_ForNonTopLevelModel_IfModelIsMarkedWithBinderMetadata()
         {
+            // Get the property metadata so that it is not a top level object.
             var modelMetadata = GetMetadataForType(typeof(Document))
-                                        .Properties
-                                        .First(metadata => metadata.PropertyName == nameof(Document.SubDocument));
+                .Properties
+                .First(metadata => metadata.PropertyName == nameof(Document.SubDocument));
             var bindingContext = new MutableObjectBinderContext
             {
                 ModelBindingContext = new ModelBindingContext
                 {
-                    // Get the property metadata so that it is not a top level object.
-                    ModelMetadata = GetMetadataForType(typeof(Document))
-                                        .Properties
-                                        .First(metadata => metadata.PropertyName == nameof(Document.SubDocument)),
+                    ModelMetadata = modelMetadata,
                     OperationBindingContext = new OperationBindingContext
                     {
                         ValidatorProvider = Mock.Of<IModelValidatorProvider>(),
@@ -381,7 +378,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
                 .Verifiable();
             testableBinder
                 .Setup(o => o.GetMetadataForProperties(bindingContext))
-                              .Returns(new ModelMetadata[0]);
+                .Returns(new ModelMetadata[0]);
 
             // Act
             var retValue = await testableBinder.Object.BindModelAsync(bindingContext);
@@ -389,8 +386,8 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             // Assert
             Assert.NotNull(retValue);
             Assert.True(retValue.IsModelSet);
-            Assert.Same(model, retValue.Model);
-            Assert.IsType<Person>(retValue.Model);
+            var returnedPerson = Assert.IsType<Person>(retValue.Model);
+            Assert.Same(model, returnedPerson);
             testableBinder.Verify();
         }
 
@@ -442,8 +439,8 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             // Assert
             Assert.NotNull(retValue);
             Assert.True(retValue.IsModelSet);
-            Assert.Same(model, retValue.Model);
-            Assert.IsType<Person>(retValue.Model);
+            var returnedPerson = Assert.IsType<Person>(retValue.Model);
+            Assert.Same(model, returnedPerson);
             testableBinder.Verify();
         }