Introducing ModelBinderFactory

This change separates model binding into IModelBinderProvider (decides
which binder to use) and IModelBinder (does binding). The
IModelBinderFactory is a new services with coordinates the creation of
model binders.

src/Microsoft.AspNetCore.Mvc.Abstractions/ModelBinding/IModelBinderProvider.cs

@@ -0,0 +1,19 @@
+// 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.
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding
+{
+    /// <summary>
+    /// Creates <see cref="IModelBinder"/> instances. Register <see cref="IModelBinderProvider"/>
+    /// instances in <c>MvcOptions</c>.
+    /// </summary>
+    public interface IModelBinderProvider
+    {
+        /// <summary>
+        /// Creates a <see cref="IModelBinder"/> based on <see cref="ModelBinderProviderContext"/>.
+        /// </summary>
+        /// <param name="context">The <see cref="ModelBinderProviderContext"/>.</param>
+        /// <returns>An <see cref="IModelBinder"/>.</returns>
+        IModelBinder GetBinder(ModelBinderProviderContext context);
+    }
+}

src/Microsoft.AspNetCore.Mvc.Abstractions/ModelBinding/Metadata/ModelMetadataIdentity.cs

@@ -3,13 +3,14 @@
 
 using System;
 using Microsoft.AspNetCore.Mvc.Abstractions;
+using Microsoft.Extensions.Internal;
 
 namespace Microsoft.AspNetCore.Mvc.ModelBinding.Metadata
 {
     /// <summary>
     /// A key type which identifies a <see cref="ModelMetadata"/>.
     /// </summary>
-    public struct ModelMetadataIdentity
+    public struct ModelMetadataIdentity : IEquatable<ModelMetadataIdentity>
     {
         /// <summary>
         /// Creates a <see cref="ModelMetadataIdentity"/> for the provided model <see cref="Type"/>.
@@ -98,5 +99,31 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Metadata
         /// the current instance represents a type.
         /// </summary>
         public string Name { get; private set; }
+
+        /// <inheritdoc />
+        public bool Equals(ModelMetadataIdentity other)
+        {
+            return
+                ContainerType == other.ContainerType &&
+                ModelType == other.ModelType &&
+                Name == other.Name;
+        }
+
+        /// <inheritdoc />
+        public override bool Equals(object obj)
+        {
+            var other = obj as ModelMetadataIdentity?;
+            return other.HasValue && Equals(other.Value);
+        }
+
+        /// <inheritdoc />
+        public override int GetHashCode()
+        {
+            var hash = new HashCodeCombiner();
+            hash.Add(ContainerType);
+            hash.Add(ModelType);
+            hash.Add(Name, StringComparer.Ordinal);
+            return hash;
+        }
     }
 }

src/Microsoft.AspNetCore.Mvc.Abstractions/ModelBinding/ModelBinderProviderContext.cs

@@ -0,0 +1,33 @@
+// 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.
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding
+{
+    /// <summary>
+    /// A context object for <see cref="IModelBinderProvider.GetBinder"/>.
+    /// </summary>
+    public abstract class ModelBinderProviderContext
+    {
+        /// <summary>
+        /// Creates an <see cref="IModelBinder"/> for the given <paramref name="metadata"/>.
+        /// </summary>
+        /// <param name="metadata">The <see cref="ModelMetadata"/> for the model.</param>
+        /// <returns>An <see cref="IModelBinder"/>.</returns>
+        public abstract IModelBinder CreateBinder(ModelMetadata metadata);
+
+        /// <summary>
+        /// Gets the <see cref="BindingInfo"/>. May be <c>null</c>.
+        /// </summary>
+        public abstract BindingInfo BindingInfo { get; }
+
+        /// <summary>
+        /// Gets the <see cref="ModelMetadata"/>.
+        /// </summary>
+        public abstract ModelMetadata Metadata { get; }
+
+        /// <summary>
+        /// Gets the <see cref="IModelMetadataProvider"/>.
+        /// </summary>
+        public abstract IModelMetadataProvider MetadataProvider { get; }
+    }
+}

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

@@ -16,28 +16,12 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         /// </summary>
         public abstract string BinderModelName { get; set; }
 
-        /// <summary>
-        /// Gets the <see cref="Type"/> of an <see cref="IModelBinder"/> associated with the
-        /// <see cref="Model"/>.
-        /// </summary>
-        public abstract Type BinderType { get; set; }
-
         /// <summary>
         /// Gets or sets a value which represents the <see cref="ModelBinding.BindingSource"/> associated with the
         /// <see cref="Model"/>.
         /// </summary>
         public abstract BindingSource BindingSource { get; set; }
 
-        /// <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 <see cref="ModelName"/> prefix.
-        /// </summary>
-        /// <remarks>
-        /// Passed into the model binding system. Should not be <c>true</c> when <see cref="IsTopLevelObject"/> is
-        /// <c>false</c>.
-        /// </remarks>
-        public abstract bool FallbackToEmptyPrefix { get; set; }
-
         /// <summary>
         /// Gets or sets the name of the current field being bound.
         /// </summary>

src/Microsoft.AspNetCore.Mvc.Abstractions/ModelBinding/ModelMetadata.cs

@@ -16,7 +16,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
     /// A metadata representation of a model type, property or parameter.
     /// </summary>
     [DebuggerDisplay("{DebuggerToString(),nq}")]
-    public abstract class ModelMetadata
+    public abstract class ModelMetadata : IEquatable<ModelMetadata>
     {
         /// <summary>
         /// The default value of <see cref="ModelMetadata.Order"/>.
@@ -378,6 +378,36 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             return DisplayName ?? PropertyName ?? ModelType.Name;
         }
 
+        /// <inheritdoc />
+        public bool Equals(ModelMetadata other)
+        {
+            if (object.ReferenceEquals(this, other))
+            {
+                return true;
+            }
+
+            if (other == null)
+            {
+                return false;
+            }
+            else
+            {
+                return Identity.Equals(other.Identity);
+            }
+        }
+
+        /// <inheritdoc />
+        public override bool Equals(object obj)
+        {
+            return base.Equals(obj as ModelMetadata);
+        }
+
+        /// <inheritdoc />
+        public override int GetHashCode()
+        {
+            return Identity.GetHashCode();
+        }
+
         private void InitializeTypeInformation()
         {
             Debug.Assert(ModelType != null);

src/Microsoft.AspNetCore.Mvc.Abstractions/ModelBinding/OperationBindingContext.cs

@@ -35,11 +35,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         /// </summary>
         public IValueProvider ValueProvider { get; set; }
 
-        /// <summary>
-        /// Gets or sets the <see cref="IModelBinder"/> associated with this context.
-        /// </summary>
-        public IModelBinder ModelBinder { get; set; }
-
         /// <summary>
         /// Gets or sets the <see cref="IModelMetadataProvider"/> associated with this context.
         /// </summary>

src/Microsoft.AspNetCore.Mvc.Core/ControllerBase.cs

@@ -27,6 +27,7 @@ namespace Microsoft.AspNetCore.Mvc
     {
         private ControllerContext _controllerContext;
         private IModelMetadataProvider _metadataProvider;
+        private IModelBinderFactory _modelBinderFactory;
         private IObjectModelValidator _objectValidator;
         private IUrlHelper _url;
 
@@ -141,6 +142,31 @@ namespace Microsoft.AspNetCore.Mvc
             }
         }
 
+        /// <summary>
+        /// Gets or sets the <see cref="IModelBinderFactory"/>.
+        /// </summary>
+        public IModelBinderFactory ModelBinderFactory
+        {
+            get
+            {
+                if (_modelBinderFactory == null)
+                {
+                    _modelBinderFactory = HttpContext?.RequestServices?.GetRequiredService<IModelBinderFactory>();
+                }
+
+                return _modelBinderFactory;
+            }
+            set
+            {
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value));
+                }
+
+                _modelBinderFactory = value;
+            }
+        }
+
         /// <summary>
         /// Gets or sets the <see cref="IUrlHelper"/>.
         /// </summary>
@@ -1139,7 +1165,7 @@ namespace Microsoft.AspNetCore.Mvc
                 prefix,
                 ControllerContext,
                 MetadataProvider,
-                new CompositeModelBinder(ControllerContext.ModelBinders),
+                ModelBinderFactory,
                 valueProvider,
                 ControllerContext.InputFormatters,
                 ObjectValidator,
@@ -1179,7 +1205,7 @@ namespace Microsoft.AspNetCore.Mvc
                 prefix,
                 ControllerContext,
                 MetadataProvider,
-                new CompositeModelBinder(ControllerContext.ModelBinders),
+                ModelBinderFactory,
                 new CompositeValueProvider(ControllerContext.ValueProviders),
                 ControllerContext.InputFormatters,
                 ObjectValidator,
@@ -1219,7 +1245,7 @@ namespace Microsoft.AspNetCore.Mvc
                 prefix,
                 ControllerContext,
                 MetadataProvider,
-                new CompositeModelBinder(ControllerContext.ModelBinders),
+                ModelBinderFactory,
                 new CompositeValueProvider(ControllerContext.ValueProviders),
                 ControllerContext.InputFormatters,
                 ObjectValidator,
@@ -1267,7 +1293,7 @@ namespace Microsoft.AspNetCore.Mvc
                 prefix,
                 ControllerContext,
                 MetadataProvider,
-                new CompositeModelBinder(ControllerContext.ModelBinders),
+                ModelBinderFactory,
                 valueProvider,
                 ControllerContext.InputFormatters,
                 ObjectValidator,
@@ -1314,7 +1340,7 @@ namespace Microsoft.AspNetCore.Mvc
                 prefix,
                 ControllerContext,
                 MetadataProvider,
-                new CompositeModelBinder(ControllerContext.ModelBinders),
+                ModelBinderFactory,
                 valueProvider,
                 ControllerContext.InputFormatters,
                 ObjectValidator,
@@ -1353,7 +1379,7 @@ namespace Microsoft.AspNetCore.Mvc
                 prefix,
                 ControllerContext,
                 MetadataProvider,
-                new CompositeModelBinder(ControllerContext.ModelBinders),
+                ModelBinderFactory,
                 new CompositeValueProvider(ControllerContext.ValueProviders),
                 ControllerContext.InputFormatters,
                 ObjectValidator,
@@ -1405,7 +1431,7 @@ namespace Microsoft.AspNetCore.Mvc
                 prefix,
                 ControllerContext,
                 MetadataProvider,
-                new CompositeModelBinder(ControllerContext.ModelBinders),
+                ModelBinderFactory,
                 valueProvider,
                 ControllerContext.InputFormatters,
                 ObjectValidator,

src/Microsoft.AspNetCore.Mvc.Core/ControllerContext.cs

@@ -17,7 +17,6 @@ namespace Microsoft.AspNetCore.Mvc
     public class ControllerContext : ActionContext
     {
         private FormatterCollection<IInputFormatter> _inputFormatters;
-        private IList<IModelBinder> _modelBinders;
         private IList<IModelValidatorProvider> _validatorProviders;
         private IList<IValueProvider> _valueProviders;
 
@@ -81,31 +80,6 @@ namespace Microsoft.AspNetCore.Mvc
             }
         }
 
-        /// <summary>
-        /// Gets or sets the list of <see cref="IModelBinder"/> instances for the current request.
-        /// </summary>
-        public virtual IList<IModelBinder> ModelBinders
-        {
-            get
-            {
-                if (_modelBinders == null)
-                {
-                    _modelBinders = new List<IModelBinder>();
-                }
-
-                return _modelBinders;
-            }
-            set
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException(nameof(value));
-                }
-
-                _modelBinders = value;
-            }
-        }
-
         /// <summary>
         /// Gets or sets the list of <see cref="IModelValidatorProvider"/> instances for the current request.
         /// </summary>

src/Microsoft.AspNetCore.Mvc.Core/DependencyInjection/MvcCoreServiceCollectionExtensions.cs

@@ -143,6 +143,7 @@ namespace Microsoft.Extensions.DependencyInjection
                 var options = serviceProvider.GetRequiredService<IOptions<MvcOptions>>().Value;
                 return new DefaultCompositeMetadataDetailsProvider(options.ModelMetadataDetailsProviders);
             }));
+            services.TryAddSingleton<IModelBinderFactory, ModelBinderFactory>();
             services.TryAddSingleton<IObjectModelValidator, DefaultObjectValidator>();
             services.TryAddSingleton<ValidatorCache>();
             services.TryAddSingleton<ClientValidatorCache>();

src/Microsoft.AspNetCore.Mvc.Core/Internal/ControllerActionInvoker.cs

@@ -32,7 +32,6 @@ namespace Microsoft.AspNetCore.Mvc.Internal
             ControllerActionDescriptor descriptor,
             IReadOnlyList<IInputFormatter> inputFormatters,
             IControllerActionArgumentBinder argumentBinder,
-            IReadOnlyList<IModelBinder> modelBinders,
             IReadOnlyList<IModelValidatorProvider> modelValidatorProviders,
             IReadOnlyList<IValueProviderFactory> valueProviderFactories,
             ILogger logger,
@@ -42,7 +41,6 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                   actionContext,
                   controllerActionInvokerCache,
                   inputFormatters,
-                  modelBinders,
                   modelValidatorProviders,
                   valueProviderFactories,
                   logger,

src/Microsoft.AspNetCore.Mvc.Core/Internal/ControllerActionInvokerProvider.cs

@@ -21,7 +21,6 @@ namespace Microsoft.AspNetCore.Mvc.Internal
         private readonly IControllerFactory _controllerFactory;
         private readonly ControllerActionInvokerCache _controllerActionInvokerCache;
         private readonly IReadOnlyList<IInputFormatter> _inputFormatters;
-        private readonly IReadOnlyList<IModelBinder> _modelBinders;
         private readonly IReadOnlyList<IModelValidatorProvider> _modelValidatorProviders;
         private readonly IReadOnlyList<IValueProviderFactory> _valueProviderFactories;
         private readonly int _maxModelValidationErrors;
@@ -40,7 +39,6 @@ namespace Microsoft.AspNetCore.Mvc.Internal
             _controllerActionInvokerCache = controllerActionInvokerCache;
             _argumentBinder = argumentBinder;
             _inputFormatters = optionsAccessor.Value.InputFormatters.ToArray();
-            _modelBinders = optionsAccessor.Value.ModelBinders.ToArray();
             _modelValidatorProviders = optionsAccessor.Value.ModelValidatorProviders.ToArray();
             _valueProviderFactories = optionsAccessor.Value.ValueProviderFactories.ToArray();
             _maxModelValidationErrors = optionsAccessor.Value.MaxModelValidationErrors;
@@ -72,7 +70,6 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                     actionDescriptor,
                     _inputFormatters,
                     _argumentBinder,
-                    _modelBinders,
                     _modelValidatorProviders,
                     _valueProviderFactories,
                     _logger,

src/Microsoft.AspNetCore.Mvc.Core/Internal/ControllerArgumentBinder.cs

@@ -24,14 +24,17 @@ namespace Microsoft.AspNetCore.Mvc.Internal
             typeof(ControllerArgumentBinder).GetTypeInfo().GetDeclaredMethod(
                 nameof(CallPropertyAddRange));
 
+        private readonly IModelBinderFactory _modelBinderFactory;
         private readonly IModelMetadataProvider _modelMetadataProvider;
         private readonly IObjectModelValidator _validator;
 
         public ControllerArgumentBinder(
             IModelMetadataProvider modelMetadataProvider,
+            IModelBinderFactory modelBinderFactory,
             IObjectModelValidator validator)
         {
             _modelMetadataProvider = modelMetadataProvider;
+            _modelBinderFactory = modelBinderFactory;
             _validator = validator;
         }
 
@@ -118,7 +121,31 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                 parameter.BindingInfo,
                 parameter.Name);
 
-            await operationContext.ModelBinder.BindModelAsync(modelBindingContext);
+            if (parameter.BindingInfo?.BinderModelName != null)
+            {
+                // The name was set explicitly, always use that as the prefix.
+                modelBindingContext.ModelName = parameter.BindingInfo.BinderModelName;
+            }
+            else if (modelBindingContext.ValueProvider.ContainsPrefix(parameter.Name))
+            {
+                // We have a match for the parameter name, use that as that prefix.
+                modelBindingContext.ModelName = parameter.Name;
+            }
+            else
+            {
+                // No match, fallback to empty string as the prefix.
+                modelBindingContext.ModelName = string.Empty;
+            }
+
+            var binder = _modelBinderFactory.CreateBinder(new ModelBinderFactoryContext()
+            {
+                BindingInfo = parameter.BindingInfo,
+                Metadata = metadata,
+                CacheToken = parameter,
+            });
+
+            await binder.BindModelAsync(modelBindingContext);
+
             var modelBindingResult = modelBindingContext.Result;
             if (modelBindingResult != null && modelBindingResult.Value.IsModelSet)
             {
@@ -241,7 +268,6 @@ namespace Microsoft.AspNetCore.Mvc.Internal
             {
                 ActionContext = context,
                 InputFormatters = context.InputFormatters,
-                ModelBinder = new CompositeModelBinder(context.ModelBinders),
                 ValidatorProvider = new CompositeModelValidatorProvider(context.ValidatorProviders),
                 MetadataProvider = _modelMetadataProvider,
                 ValueProvider = new CompositeValueProvider(context.ValueProviders),

src/Microsoft.AspNetCore.Mvc.Core/Internal/DefaultModelBindingContext.cs

@@ -12,6 +12,8 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
     /// </summary>
     public class DefaultModelBindingContext : ModelBindingContext
     {
+        private OperationBindingContext _operationBindingContext;
+
         private State _state;
         private readonly Stack<State> _stack = new Stack<State>();
 
@@ -57,17 +59,19 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             var propertyPredicateProvider =
                 bindingInfo?.PropertyBindingPredicateProvider ?? metadata.PropertyBindingPredicateProvider;
 
+            var valueProvider = operationBindingContext.ValueProvider;
+            var bindingSource = bindingInfo?.BindingSource ?? metadata.BindingSource;
+            if (bindingSource != null && !bindingSource.IsGreedy)
+            {
+                valueProvider = FilterValueProvider(operationBindingContext.ValueProvider, bindingSource);
+            }
+
             return new DefaultModelBindingContext()
             {
                 BinderModelName = binderModelName,
-                BindingSource = bindingInfo?.BindingSource ?? metadata.BindingSource,
+                BindingSource = bindingSource,
-                BinderType = bindingInfo?.BinderType ?? metadata.BinderType,
                 PropertyFilter = propertyPredicateProvider?.PropertyFilter,
 
-                // We only support fallback to empty prefix in cases where the model name is inferred from
-                // the parameter or property being bound.
-                FallbackToEmptyPrefix = binderModelName == null,
-
                 // Because this is the top-level context, FieldName and ModelName should be the same.
                 FieldName = binderModelName ?? modelName,
                 ModelName = binderModelName ?? modelName,
@@ -76,7 +80,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 ModelMetadata = metadata,
                 ModelState = operationBindingContext.ActionContext.ModelState,
                 OperationBindingContext = operationBindingContext,
-                ValueProvider = operationBindingContext.ValueProvider,
+                ValueProvider = valueProvider,
 
                 ValidationState = new ValidationStateDictionary(),
             };
@@ -106,16 +110,21 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
 
             var scope = EnterNestedScope();
 
+            // Only filter if the new BindingSource affects the value providers. Otherwise we want
+            // to preserve the currrent state.
+            if (modelMetadata.BindingSource != null && !modelMetadata.BindingSource.IsGreedy)
+            {
+                ValueProvider = FilterValueProvider(_operationBindingContext.ValueProvider, modelMetadata.BindingSource);
+            }
+
             Model = model;
             ModelMetadata = modelMetadata;
             ModelName = modelName;
             FieldName = fieldName;
             BinderModelName = modelMetadata.BinderModelName;
-            BinderType = modelMetadata.BinderType;
             BindingSource = modelMetadata.BindingSource;
             PropertyFilter = modelMetadata.PropertyBindingPredicateProvider?.PropertyFilter;
 
-            FallbackToEmptyPrefix = false;
             IsTopLevelObject = false;
 
             return scope;
@@ -140,14 +149,14 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         /// <inheritdoc />
         public override OperationBindingContext OperationBindingContext
         {
-            get { return _state.OperationBindingContext; }
+            get { return _operationBindingContext; }
             set
             {
                 if (value == null)
                 {
                     throw new ArgumentNullException(nameof(value));
                 }
-                _state.OperationBindingContext = value;
+                _operationBindingContext = value;
             }
         }
 
@@ -231,20 +240,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             set { _state.BindingSource = value; }
         }
 
-        /// <inheritdoc />
-        public override Type BinderType
-        {
-            get { return _state.BinderType; }
-            set { _state.BinderType = value; }
-        }
-
-        /// <inheritdoc />
-        public override bool FallbackToEmptyPrefix
-        {
-            get { return _state.FallbackToEmptyPrefix; }
-            set { _state.FallbackToEmptyPrefix = value; }
-        }
-
         /// <inheritdoc />
         public override bool IsTopLevelObject
         {
@@ -298,9 +293,24 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             }
         }
 
+        private static IValueProvider FilterValueProvider(IValueProvider valueProvider, BindingSource bindingSource)
+        {
+            if (bindingSource == null || bindingSource.IsGreedy)
+            {
+                return valueProvider;
+            }
+
+            var bindingSourceValueProvider = valueProvider as IBindingSourceValueProvider;
+            if (bindingSourceValueProvider == null)
+            {
+                return valueProvider;
+            }
+
+            return bindingSourceValueProvider.Filter(bindingSource) ?? new CompositeValueProvider();
+        }
+
         private struct State
         {
-            public OperationBindingContext OperationBindingContext;
             public string FieldName;
             public object Model;
             public ModelMetadata ModelMetadata;
@@ -313,8 +323,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
 
             public string BinderModelName;
             public BindingSource BindingSource;
-            public Type BinderType;
-            public bool FallbackToEmptyPrefix;
             public bool IsTopLevelObject;
 
             public ModelBindingResult? Result;

src/Microsoft.AspNetCore.Mvc.Core/Internal/FilterActionInvoker.cs

@@ -20,7 +20,6 @@ namespace Microsoft.AspNetCore.Mvc.Internal
     {
         private readonly ControllerActionInvokerCache _controllerActionInvokerCache;
         private readonly IReadOnlyList<IInputFormatter> _inputFormatters;
-        private readonly IReadOnlyList<IModelBinder> _modelBinders;
         private readonly IReadOnlyList<IModelValidatorProvider> _modelValidatorProviders;
         private readonly IReadOnlyList<IValueProviderFactory> _valueProviderFactories;
         private readonly DiagnosticSource _diagnosticSource;
@@ -47,7 +46,6 @@ namespace Microsoft.AspNetCore.Mvc.Internal
             ActionContext actionContext,
             ControllerActionInvokerCache controllerActionInvokerCache,
             IReadOnlyList<IInputFormatter> inputFormatters,
-            IReadOnlyList<IModelBinder> modelBinders,
             IReadOnlyList<IModelValidatorProvider> modelValidatorProviders,
             IReadOnlyList<IValueProviderFactory> valueProviderFactories,
             ILogger logger,
@@ -69,11 +67,6 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                 throw new ArgumentNullException(nameof(inputFormatters));
             }
 
-            if (modelBinders == null)
-            {
-                throw new ArgumentNullException(nameof(modelBinders));
-            }
-
             if (modelValidatorProviders == null)
             {
                 throw new ArgumentNullException(nameof(modelValidatorProviders));
@@ -98,7 +91,6 @@ namespace Microsoft.AspNetCore.Mvc.Internal
 
             _controllerActionInvokerCache = controllerActionInvokerCache;
             _inputFormatters = inputFormatters;
-            _modelBinders = modelBinders;
             _modelValidatorProviders = modelValidatorProviders;
             _valueProviderFactories = valueProviderFactories;
             Logger = logger;
@@ -356,7 +348,6 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                     // binding.
                     Context.InputFormatters = new FormatterCollection<IInputFormatter>(
                         new CopyOnWriteList<IInputFormatter>(_inputFormatters));
-                    Context.ModelBinders = new CopyOnWriteList<IModelBinder>(_modelBinders);
                     Context.ValidatorProviders = new CopyOnWriteList<IModelValidatorProvider>(_modelValidatorProviders);
 
                     var valueProviders = new List<IValueProvider>();

src/Microsoft.AspNetCore.Mvc.Core/Internal/MvcCoreMvcOptionsSetup.cs

@@ -6,9 +6,8 @@ using System.Threading;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc.Core;
 using Microsoft.AspNetCore.Mvc.Formatters;
-using Microsoft.AspNetCore.Mvc.Infrastructure;
 using Microsoft.AspNetCore.Mvc.ModelBinding;
-using Microsoft.AspNetCore.Mvc.ModelBinding.Metadata;
+using Microsoft.AspNetCore.Mvc.ModelBinding.Binders;
 using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;
 using Microsoft.Extensions.Options;
 
@@ -37,17 +36,20 @@ namespace Microsoft.AspNetCore.Mvc.Internal
             messageProvider.ValueMustBeANumberAccessor = Resources.FormatHtmlGeneration_ValueMustBeNumber;
 
             // Set up ModelBinding
-            options.ModelBinders.Add(new BinderTypeBasedModelBinder());
+            options.ModelBinderProviders.Add(new BinderTypeModelBinderProvider());
-            options.ModelBinders.Add(new ServicesModelBinder());
+            options.ModelBinderProviders.Add(new ServicesModelBinderProvider());
-            options.ModelBinders.Add(new BodyModelBinder(readerFactory));
+            options.ModelBinderProviders.Add(new BodyModelBinderProvider(readerFactory));
-            options.ModelBinders.Add(new HeaderModelBinder());
+            options.ModelBinderProviders.Add(new HeaderModelBinderProvider());
-            options.ModelBinders.Add(new SimpleTypeModelBinder());
+            options.ModelBinderProviders.Add(new SimpleTypeModelBinderProvider());
-            options.ModelBinders.Add(new CancellationTokenModelBinder());
+            options.ModelBinderProviders.Add(new CancellationTokenModelBinderProvider());
-            options.ModelBinders.Add(new ByteArrayModelBinder());
+            options.ModelBinderProviders.Add(new ByteArrayModelBinderProvider());
-            options.ModelBinders.Add(new FormFileModelBinder());
+            options.ModelBinderProviders.Add(new FormFileModelBinderProvider());
-            options.ModelBinders.Add(new FormCollectionModelBinder());
+            options.ModelBinderProviders.Add(new FormCollectionModelBinderProvider());
-            options.ModelBinders.Add(new GenericModelBinder());
+            options.ModelBinderProviders.Add(new KeyValuePairModelBinderProvider());
-            options.ModelBinders.Add(new MutableObjectModelBinder());
+            options.ModelBinderProviders.Add(new DictionaryModelBinderProvider());
+            options.ModelBinderProviders.Add(new ArrayModelBinderProvider());
+            options.ModelBinderProviders.Add(new CollectionModelBinderProvider());
+            options.ModelBinderProviders.Add(new ComplexTypeModelBinderProvider());
 
             // Set up filters
             options.Filters.Add(new UnsupportedContentTypeFilter());

src/Microsoft.AspNetCore.Mvc.Core/Internal/PlaceholderBinder.cs

@@ -0,0 +1,21 @@
+// 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.Threading.Tasks;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Internal
+{
+    // Used as a placeholder to break cycles while building a tree of model binders in ModelBinderFactory.
+    //
+    // When a cycle is detected by a call to Create(...), we create an instance of this class and return it
+    // to break the cycle. Later when the 'real' binder is created we set Inner to point to that.
+    public class PlaceholderBinder : IModelBinder
+    {
+        public IModelBinder Inner { get; set; }
+
+        public Task BindModelAsync(ModelBindingContext bindingContext)
+        {
+            return Inner.BindModelAsync(bindingContext);
+        }
+    }
+}

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

@@ -1,71 +0,0 @@
-// 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;
-using System.Collections.Concurrent;
-using System.Threading.Tasks;
-using Microsoft.AspNetCore.Mvc.Core;
-using Microsoft.AspNetCore.Mvc.Internal;
-using Microsoft.Extensions.DependencyInjection;
-
-namespace Microsoft.AspNetCore.Mvc.ModelBinding
-{
-    /// <summary>
-    /// An <see cref="IModelBinder"/> which can bind a model based on the value of 
-    /// <see cref="ModelMetadata.BinderType"/>. The supplied <see cref="IModelBinder"/> 
-    /// type will be used to bind the model.
-    /// </summary>
-    public class BinderTypeBasedModelBinder : IModelBinder
-    {
-        private readonly Func<Type, ObjectFactory> _createFactory =
-            (t) => ActivatorUtilities.CreateFactory(t, Type.EmptyTypes);
-        private readonly ConcurrentDictionary<Type, ObjectFactory> _typeActivatorCache =
-               new ConcurrentDictionary<Type, ObjectFactory>();
-
-        public Task BindModelAsync(ModelBindingContext bindingContext)
-        {
-            if (bindingContext == null)
-            {
-                throw new ArgumentNullException(nameof(bindingContext));
-            }
-
-            // This method is optimized to use cached tasks when possible and avoid allocating
-            // using Task.FromResult. If you need to make changes of this nature, profile
-            // allocations afterwards and look for Task<ModelBindingResult>.
-
-            if (bindingContext.BinderType == null)
-            {
-                // Return null so that we are able to continue with the default set of model binders,
-                // if there is no specific model binder provided.
-                return TaskCache.CompletedTask;
-            }
-
-            return BindModelCoreAsync(bindingContext);
-        }
-
-        private async Task BindModelCoreAsync(ModelBindingContext bindingContext)
-        {
-            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)
-            {
-                throw new InvalidOperationException(
-                    Resources.FormatBinderType_MustBeIModelBinder(
-                        bindingContext.BinderType.FullName,
-                        typeof(IModelBinder).FullName));
-            }
-
-            await modelBinder.BindModelAsync(bindingContext);
-
-            // 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.
-            if (bindingContext.Result == null)
-            {
-                bindingContext.Result = ModelBindingResult.Failed(bindingContext.ModelName);
-            }
-        }
-    }
-}

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/ArrayModelBinder.cs

@@ -5,10 +5,8 @@ using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
-using System.Threading.Tasks;
-using Microsoft.AspNetCore.Mvc.Internal;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
     /// <summary>
     /// <see cref="IModelBinder"/> implementation for binding array values.
@@ -16,20 +14,15 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
     /// <typeparam name="TElement">Type of elements in the array.</typeparam>
     public class ArrayModelBinder<TElement> : CollectionModelBinder<TElement>
     {
-        /// <inheritdoc />
+        /// <summary>
-        public override Task BindModelAsync(ModelBindingContext bindingContext)
+        /// Creates a new <see cref="ArrayModelBinder{TElement}"/>.
+        /// </summary>
+        /// <param name="elementBinder">
+        /// The <see cref="IModelBinder"/> for binding <typeparamref name="TElement"/>.
+        /// </param>
+        public ArrayModelBinder(IModelBinder elementBinder)
+            : base(elementBinder)
         {
-            if (bindingContext == null)
-            {
-                throw new ArgumentNullException(nameof(bindingContext));
-            }
-
-            if (bindingContext.ModelMetadata.IsReadOnly)
-            {
-                return TaskCache.CompletedTask;
-            }
-
-            return base.BindModelAsync(bindingContext);
         }
 
         /// <inheritdoc />
@@ -62,8 +55,9 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             {
                 throw new ArgumentNullException(nameof(target));
             }
+
             // Do not attempt to copy values into an array because an array's length is immutable. This choice is also
-            // consistent with MutableObjectModelBinder's handling of a read-only array property.
+            // consistent with our handling of a read-only array property.
         }
     }
 }

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/ArrayModelBinderProvider.cs

@@ -0,0 +1,35 @@
+// 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;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    /// <summary>
+    /// An <see cref="IModelBinderProvider"/> for arrays.
+    /// </summary>
+    public class ArrayModelBinderProvider : IModelBinderProvider
+    {
+        /// <inheritdoc />
+        public IModelBinder GetBinder(ModelBinderProviderContext context)
+        {
+            if (context == null)
+            {
+                throw new ArgumentNullException(nameof(context));
+            }
+
+            // We don't support binding readonly properties of arrays because we can't resize the
+            // existing value.
+            if (context.Metadata.ModelType.IsArray && !context.Metadata.IsReadOnly)
+            {
+                var elementType = context.Metadata.ElementMetadata.ModelType;
+                var elementBinder = context.CreateBinder(context.Metadata.ElementMetadata);
+
+                var binderType = typeof(ArrayModelBinder<>).MakeGenericType(elementType);
+                return (IModelBinder)Activator.CreateInstance(binderType, elementBinder);
+            }
+
+            return null;
+        }
+    }
+}

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/BinderTypeModelBinder.cs

@@ -0,0 +1,62 @@
+// 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;
+using System.Reflection;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Mvc.Core;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    /// <summary>
+    /// An <see cref="IModelBinder"/> for models which specify an <see cref="IModelBinder"/> using
+    /// <see cref="BindingInfo.BinderType"/>.
+    /// </summary>
+    public class BinderTypeModelBinder : IModelBinder
+    {
+        private readonly ObjectFactory _factory;
+
+        /// <summary>
+        /// Creates a new <see cref="BinderTypeModelBinder"/>.
+        /// </summary>
+        /// <param name="binderType">The <see cref="Type"/> of the <see cref="IModelBinder"/>.</param>
+        public BinderTypeModelBinder(Type binderType)
+        {
+            if (binderType == null)
+            {
+                throw new ArgumentNullException(nameof(binderType));
+            }
+
+            if (!typeof(IModelBinder).GetTypeInfo().IsAssignableFrom(binderType.GetTypeInfo()))
+            {
+                throw new ArgumentException(
+                    Resources.FormatBinderType_MustBeIModelBinder(
+                        binderType.FullName,
+                        typeof(IModelBinder).FullName),
+                    nameof(binderType));
+            }
+
+            _factory = ActivatorUtilities.CreateFactory(binderType, Type.EmptyTypes);
+        }
+
+        /// <inheritdoc />
+        public async Task BindModelAsync(ModelBindingContext bindingContext)
+        {
+            if (bindingContext == null)
+            {
+                throw new ArgumentNullException(nameof(bindingContext));
+            }
+
+            var requestServices = bindingContext.OperationBindingContext.HttpContext.RequestServices;
+            var binder = (IModelBinder)_factory(requestServices, arguments: null);
+
+            await binder.BindModelAsync(bindingContext);
+
+            if (bindingContext.Result == null)
+            {
+                bindingContext.Result = ModelBindingResult.Failed(bindingContext.ModelName);
+            }
+        }
+    }
+}

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/BinderTypeModelBinderProvider.cs

@@ -0,0 +1,30 @@
+// 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;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    /// <summary>
+    /// An <see cref="IModelBinderProvider"/> for models which specify an <see cref="IModelBinder"/>
+    /// using <see cref="BindingInfo.BinderType"/>.
+    /// </summary>
+    public class BinderTypeModelBinderProvider : IModelBinderProvider
+    {
+        /// <inheritdoc />
+        public IModelBinder GetBinder(ModelBinderProviderContext context)
+        {
+            if (context == null)
+            {
+                throw new ArgumentNullException(nameof(context));
+            }
+
+            if (context.BindingInfo?.BinderType != null)
+            {
+                return new BinderTypeModelBinder(context.BindingInfo.BinderType);
+            }
+
+            return null;
+        }
+    }
+}

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/BodyModelBinder.cs

@@ -10,7 +10,7 @@ using Microsoft.AspNetCore.Mvc.Core;
 using Microsoft.AspNetCore.Mvc.Formatters;
 using Microsoft.AspNetCore.Mvc.Internal;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
     /// <summary>
     /// An <see cref="IModelBinder"/> which binds models from the request body using an <see cref="IInputFormatter"/>
@@ -33,37 +33,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         }
 
         /// <inheritdoc />
-        public Task BindModelAsync(ModelBindingContext bindingContext)
+        public async Task BindModelAsync(ModelBindingContext bindingContext)
-        {
-            if (bindingContext == null)
-            {
-                throw new ArgumentNullException(nameof(bindingContext));
-            }
-
-            // This method is optimized to use cached tasks when possible and avoid allocating
-            // using Task.FromResult. If you need to make changes of this nature, profile
-            // allocations afterwards and look for Task<ModelBindingResult>.
-
-            var allowedBindingSource = bindingContext.BindingSource;
-            if (allowedBindingSource == null ||
-                !allowedBindingSource.CanAcceptDataFrom(BindingSource.Body))
-            {
-                // Formatters are opt-in. This model either didn't specify [FromBody] or specified something
-                // incompatible so let other binders run.
-                return TaskCache.CompletedTask;
-            }
-
-            return BindModelCoreAsync(bindingContext);
-        }
-
-        /// <summary>
-        /// Attempts to bind the model using formatters.
-        /// </summary>
-        /// <param name="bindingContext">The <see cref="ModelBindingContext"/>.</param>
-        /// <returns>
-        /// A <see cref="Task{ModelBindingResult}"/> which when completed returns a <see cref="ModelBindingResult"/>.
-        /// </returns>
-        private async Task BindModelCoreAsync(ModelBindingContext bindingContext)
         {
             if (bindingContext == null)
             {

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/BodyModelBinderProvider.cs

@@ -0,0 +1,47 @@
+// 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;
+using Microsoft.AspNetCore.Mvc.Internal;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    /// <summary>
+    /// An <see cref="IModelBinderProvider"/> for deserializing the request body using a formatter.
+    /// </summary>
+    public class BodyModelBinderProvider : IModelBinderProvider
+    {
+        private readonly IHttpRequestStreamReaderFactory _readerFactory;
+
+        /// <summary>
+        /// Creates a new <see cref="BodyModelBinderProvider"/>.
+        /// </summary>
+        /// <param name="readerFactory">The <see cref="IHttpRequestStreamReaderFactory"/>.</param>
+        public BodyModelBinderProvider(IHttpRequestStreamReaderFactory readerFactory)
+        {
+            if (readerFactory == null)
+            {
+                throw new ArgumentNullException(nameof(readerFactory));
+            }
+
+            _readerFactory = readerFactory;
+        }
+
+        /// <inheritdoc />
+        public IModelBinder GetBinder(ModelBinderProviderContext context)
+        {
+            if (context == null)
+            {
+                throw new ArgumentNullException(nameof(context));
+            }
+
+            if (context.BindingInfo?.BindingSource != null &&
+                context.BindingInfo.BindingSource.CanAcceptDataFrom(BindingSource.Body))
+            {
+                return new BodyModelBinder(_readerFactory);
+            }
+
+            return null;
+        }
+    }
+}

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/ByteArrayModelBinder.cs

@@ -5,10 +5,10 @@ using System;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Mvc.Internal;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
     /// <summary>
-    /// ModelBinder to bind Byte Arrays.
+    /// ModelBinder to bind byte Arrays.
     /// </summary>
     public class ByteArrayModelBinder : IModelBinder
     {
@@ -20,16 +20,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 throw new ArgumentNullException(nameof(bindingContext));
             }
 
-            // This method is optimized to use cached tasks when possible and avoid allocating
-            // using Task.FromResult. If you need to make changes of this nature, profile
-            // allocations afterwards and look for Task<ModelBindingResult>.
-
-            // Check if this binder applies.
-            if (bindingContext.ModelType != typeof(byte[]))
-            {
-                return TaskCache.CompletedTask;
-            }
-
             // Check for missing data case 1: There was no <input ... /> element containing this data.
             var valueProviderResult = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);
             if (valueProviderResult == ValueProviderResult.None)

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/ByteArrayModelBinderProvider.cs

@@ -0,0 +1,29 @@
+// 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;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    /// <summary>
+    /// An <see cref="IModelBinderProvider"/> for binding base64 encoded byte arrays.
+    /// </summary>
+    public class ByteArrayModelBinderProvider : IModelBinderProvider
+    {
+        /// <inheritdoc />
+        public IModelBinder GetBinder(ModelBinderProviderContext context)
+        {
+            if (context == null)
+            {
+                throw new ArgumentNullException(nameof(context));
+            }
+
+            if (context.Metadata.ModelType == typeof(byte[]))
+            {
+                return new ByteArrayModelBinder();
+            }
+
+            return null;
+        }
+    }
+}

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/CancellationTokenModelBinder.cs

@@ -7,7 +7,7 @@ using System.Threading.Tasks;
 using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;
 using Microsoft.AspNetCore.Mvc.Internal;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
     /// <summary>
     /// <see cref="IModelBinder"/> implementation to bind models of type <see cref="CancellationToken"/>.
@@ -22,16 +22,13 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 throw new ArgumentNullException(nameof(bindingContext));
             }
 
-            if (bindingContext.ModelType == typeof(CancellationToken))
+            // We need to force boxing now, so we can insert the same reference to the boxed CancellationToken
-            {
+            // in both the ValidationState and ModelBindingResult.
-                // We need to force boxing now, so we can insert the same reference to the boxed CancellationToken
+            //
-                // in both the ValidationState and ModelBindingResult.
+            // DO NOT simplify this code by removing the cast.
-                //
+            var model = (object)bindingContext.OperationBindingContext.HttpContext.RequestAborted;
-                // DO NOT simplify this code by removing the cast.
+            bindingContext.ValidationState.Add(model, new ValidationStateEntry() { SuppressValidation = true });
-                var model = (object)bindingContext.OperationBindingContext.HttpContext.RequestAborted;
+            bindingContext.Result = ModelBindingResult.Success(bindingContext.ModelName, model);
-                bindingContext.ValidationState.Add(model, new ValidationStateEntry() { SuppressValidation = true });
-                bindingContext.Result = ModelBindingResult.Success(bindingContext.ModelName, model);
-            }
 
             return TaskCache.CompletedTask;
         }

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/CancellationTokenModelBinderProvider.cs

@@ -0,0 +1,30 @@
+// 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;
+using System.Threading;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    /// <summary>
+    /// An <see cref="IModelBinderProvider"/> for <see cref="CancellationToken"/>.
+    /// </summary>
+    public class CancellationTokenModelBinderProvider : IModelBinderProvider
+    {
+        /// <inheritdoc />
+        public IModelBinder GetBinder(ModelBinderProviderContext context)
+        {
+            if (context == null)
+            {
+                throw new ArgumentNullException(nameof(context));
+            }
+
+            if (context.Metadata.ModelType == typeof(CancellationToken))
+            {
+                return new CancellationTokenModelBinder();
+            }
+
+            return null;
+        }
+    }
+}

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/CollectionModelBinder.cs

@@ -12,7 +12,7 @@ using System.Threading.Tasks;
 using Microsoft.AspNetCore.Mvc.Internal;
 using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
     /// <summary>
     /// <see cref="IModelBinder"/> implementation for binding collection values.
@@ -20,6 +20,25 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
     /// <typeparam name="TElement">Type of elements in the collection.</typeparam>
     public class CollectionModelBinder<TElement> : ICollectionModelBinder
     {
+        /// <summary>
+        /// Creates a new <see cref="CollectionModelBinder{TElement}"/>.
+        /// </summary>
+        /// <param name="elementBinder">The <see cref="IModelBinder"/> for binding elements.</param>
+        public CollectionModelBinder(IModelBinder elementBinder)
+        {
+            if (elementBinder == null)
+            {
+                throw new ArgumentNullException(nameof(elementBinder));
+            }
+
+            ElementBinder = elementBinder;
+        }
+
+        /// <summary>
+        /// Gets the <see cref="IModelBinder"/> instances for binding collection elements.
+        /// </summary>
+        protected IModelBinder ElementBinder { get; }
+
         /// <inheritdoc />
         public virtual async Task BindModelAsync(ModelBindingContext bindingContext)
         {
@@ -28,8 +47,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 throw new ArgumentNullException(nameof(bindingContext));
             }
 
-            ModelBindingHelper.ValidateBindingContext(bindingContext);
-
             var model = bindingContext.Model;
             if (!bindingContext.ValueProvider.ContainsPrefix(bindingContext.ModelName))
             {
@@ -163,7 +180,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                     modelName: bindingContext.ModelName,
                     model: null))
                 {
-                    await bindingContext.OperationBindingContext.ModelBinder.BindModelAsync(bindingContext);
+                    await ElementBinder.BindModelAsync(bindingContext);
 
                     if (bindingContext.Result != null && bindingContext.Result.Value.IsModelSet)
                     {
@@ -224,7 +241,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                     modelName: fullChildName,
                     model: null))
                 {
-                    await bindingContext.OperationBindingContext.ModelBinder.BindModelAsync(bindingContext);
+                    await ElementBinder.BindModelAsync(bindingContext);
                     result = bindingContext.Result;
                 }
 

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/CollectionModelBinderProvider.cs

@@ -0,0 +1,65 @@
+// 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;
+using System.Collections.Generic;
+using System.Reflection;
+using Microsoft.Extensions.Internal;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    /// <summary>
+    /// An <see cref="IModelBinderProvider"/> for <see cref="ICollection{T}"/>.
+    /// </summary>
+    public class CollectionModelBinderProvider : IModelBinderProvider
+    {
+        /// <inheritdoc />
+        public IModelBinder GetBinder(ModelBinderProviderContext context)
+        {
+            if (context == null)
+            {
+                throw new ArgumentNullException(nameof(context));
+            }
+
+            var modelType = context.Metadata.ModelType;
+            
+            // Arrays are handled by another binder.
+            if (modelType.IsArray)
+            {
+                return null;
+            }
+
+            // If the model type is ICollection<> then we can call its Add method, so we can always support it.
+            var collectionType = ClosedGenericMatcher.ExtractGenericInterface(modelType, typeof(ICollection<>));
+            if (collectionType != null)
+            {
+                var elementType = collectionType.GenericTypeArguments[0];
+                var elementBinder = context.CreateBinder(context.MetadataProvider.GetMetadataForType(elementType));
+
+                var binderType = typeof(CollectionModelBinder<>).MakeGenericType(collectionType.GenericTypeArguments);
+                return (IModelBinder)Activator.CreateInstance(binderType, elementBinder);
+            }
+
+            // If the model type is IEnumerable<> then we need to know if we can assign a List<> to it, since
+            // that's what we would create. (The cases handled here are IEnumerable<>, IReadOnlyColection<> and
+            // IReadOnlyList<>).
+            //
+            // We need to check IsReadOnly because we need to know if we can SET the property.
+            var enumerableType = ClosedGenericMatcher.ExtractGenericInterface(modelType, typeof(IEnumerable<>));
+            if (enumerableType != null && !context.Metadata.IsReadOnly)
+            {
+                var listType = typeof(List<>).MakeGenericType(enumerableType.GenericTypeArguments);
+                if (modelType.GetTypeInfo().IsAssignableFrom(listType.GetTypeInfo()))
+                {
+                    var elementType = enumerableType.GenericTypeArguments[0];
+                    var elementBinder = context.CreateBinder(context.MetadataProvider.GetMetadataForType(elementType));
+
+                    var binderType = typeof(CollectionModelBinder<>).MakeGenericType(enumerableType.GenericTypeArguments);
+                    return (IModelBinder)Activator.CreateInstance(binderType, elementBinder);
+                }
+            }
+
+            return null;
+        }
+    }
+}

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/ComplexTypeModelBinder.cs

@@ -2,17 +2,36 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Collections.Generic;
 using System.Reflection;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Mvc.Internal;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
     /// <summary>
-    /// <see cref="IModelBinder"/> implementation for binding complex values.
+    /// <see cref="IModelBinder"/> implementation for binding complex types.
     /// </summary>
-    public class MutableObjectModelBinder : IModelBinder
+    public class ComplexTypeModelBinder : IModelBinder
     {
+        private readonly IDictionary<ModelMetadata, IModelBinder> _propertyBinders;
+
+        /// <summary>
+        /// Creates a new <see cref="ComplexTypeModelBinder"/>.
+        /// </summary>
+        /// <param name="propertyBinders">
+        /// The <see cref="IDictionary{TKey, TValue}"/> of binders to use for binding properties.
+        /// </param>
+        public ComplexTypeModelBinder(IDictionary<ModelMetadata, IModelBinder> propertyBinders)
+        {
+            if (propertyBinders == null)
+            {
+                throw new ArgumentNullException(nameof(propertyBinders));
+            }
+
+            _propertyBinders = propertyBinders;
+        }
+
         /// <inheritdoc />
         public Task BindModelAsync(ModelBindingContext bindingContext)
         {
@@ -21,12 +40,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 throw new ArgumentNullException(nameof(bindingContext));
             }
 
-            ModelBindingHelper.ValidateBindingContext(bindingContext);
-            if (!CanBindType(bindingContext.ModelMetadata))
-            {
-                return TaskCache.CompletedTask;
-            }
-
             if (!CanCreateModel(bindingContext))
             {
                 return TaskCache.CompletedTask;
@@ -135,7 +148,8 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         /// </returns>
         protected virtual Task BindProperty(ModelBindingContext bindingContext)
         {
-            return bindingContext.OperationBindingContext.ModelBinder.BindModelAsync(bindingContext);
+            var binder = _propertyBinders[bindingContext.ModelMetadata];
+            return binder.BindModelAsync(bindingContext);
         }
 
         internal bool CanCreateModel(ModelBindingContext bindingContext)
@@ -284,22 +298,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             return false;
         }
 
-        private static bool CanBindType(ModelMetadata modelMetadata)
-        {
-            // Simple types cannot use this binder
-            if (!modelMetadata.IsComplexType)
-            {
-                return false;
-            }
-
-            if (modelMetadata.IsEnumerableType)
-            {
-                return false;
-            }
-
-            return true;
-        }
-
         // Internal for tests
         internal static bool CanUpdatePropertyInternal(ModelMetadata propertyMetadata)
         {

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/ComplexTypeModelBinderProvider.cs

@@ -0,0 +1,36 @@
+// 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;
+using System.Collections.Generic;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    /// <summary>
+    /// An <see cref="IModelBinderProvider"/> for complex types.
+    /// </summary>
+    public class ComplexTypeModelBinderProvider : IModelBinderProvider
+    {
+        /// <inheritdoc />
+        public IModelBinder GetBinder(ModelBinderProviderContext context)
+        {
+            if (context == null)
+            {
+                throw new ArgumentNullException(nameof(context));
+            }
+
+            if (context.Metadata.IsComplexType && !context.Metadata.IsCollectionType)
+            {
+                var propertyBinders = new Dictionary<ModelMetadata, IModelBinder>();
+                foreach (var property in context.Metadata.Properties)
+                {
+                    propertyBinders.Add(property, context.CreateBinder(property));
+                }
+
+                return new ComplexTypeModelBinder(propertyBinders);
+            }
+
+            return null;
+        }
+    }
+}

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/DictionaryModelBinder.cs

@@ -12,7 +12,7 @@ using System.Threading.Tasks;
 using Microsoft.AspNetCore.Mvc.Internal;
 using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
     /// <summary>
     /// <see cref="IModelBinder"/> implementation for binding dictionary values.
@@ -21,6 +21,24 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
     /// <typeparam name="TValue">Type of values in the dictionary.</typeparam>
     public class DictionaryModelBinder<TKey, TValue> : CollectionModelBinder<KeyValuePair<TKey, TValue>>
     {
+        private readonly IModelBinder _valueBinder;
+
+        /// <summary>
+        /// Creates a new <see cref="DictionaryModelBinder{TKey, TValue}"/>.
+        /// </summary>
+        /// <param name="keyBinder">The <see cref="IModelBinder"/> for <typeparamref name="TKey"/>.</param>
+        /// <param name="valueBinder">The <see cref="IModelBinder"/> for <typeparamref name="TValue"/>.</param>
+        public DictionaryModelBinder(IModelBinder keyBinder, IModelBinder valueBinder)
+            : base(new KeyValuePairModelBinder<TKey, TValue>(keyBinder, valueBinder))
+        {
+            if (valueBinder == null)
+            {
+                throw new ArgumentNullException(nameof(valueBinder));
+            }
+
+            _valueBinder = valueBinder;
+        }
+
         /// <inheritdoc />
         public override async Task BindModelAsync(ModelBindingContext bindingContext)
         {
@@ -66,8 +84,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             var metadataProvider = bindingContext.OperationBindingContext.MetadataProvider;
             var valueMetadata = metadataProvider.GetMetadataForType(typeof(TValue));
 
-            var modelBinder = bindingContext.OperationBindingContext.ModelBinder;
-
             var keyMappings = new Dictionary<string, TKey>(StringComparer.Ordinal);
             foreach (var kvp in keys)
             {
@@ -81,7 +97,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                     modelName: kvp.Value,
                     model: null))
                 {
-                    await modelBinder.BindModelAsync(bindingContext);
+                    await _valueBinder.BindModelAsync(bindingContext);
 
                     var valueResult = bindingContext.Result;
 

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/DictionaryModelBinderProvider.cs

@@ -0,0 +1,40 @@
+// 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;
+using System.Collections.Generic;
+using Microsoft.Extensions.Internal;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    /// <summary>
+    /// An <see cref="IModelBinderProvider"/> for binding <see cref="IDictionary{TKey, TValue}"/>.
+    /// </summary>
+    public class DictionaryModelBinderProvider : IModelBinderProvider
+    {
+        /// <inheritdoc />
+        public IModelBinder GetBinder(ModelBinderProviderContext context)
+        {
+            if (context == null)
+            {
+                throw new ArgumentNullException(nameof(context));
+            }
+
+            var modelType = context.Metadata.ModelType;
+            var dictionaryType = ClosedGenericMatcher.ExtractGenericInterface(modelType, typeof(IDictionary<,>));
+            if (dictionaryType != null)
+            {
+                var keyType = dictionaryType.GenericTypeArguments[0];
+                var keyBinder = context.CreateBinder(context.MetadataProvider.GetMetadataForType(keyType));
+
+                var valueType = dictionaryType.GenericTypeArguments[1];
+                var valueBinder = context.CreateBinder(context.MetadataProvider.GetMetadataForType(valueType));
+
+                var binderType = typeof(DictionaryModelBinder<,>).MakeGenericType(dictionaryType.GenericTypeArguments);
+                return (IModelBinder)Activator.CreateInstance(binderType, keyBinder, valueBinder);
+            }
+
+            return null;
+        }
+    }
+}

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/FormCollectionModelBinder.cs

@@ -7,11 +7,10 @@ using System.Collections.Generic;
 using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http;
-using Microsoft.AspNetCore.Mvc.Internal;
 using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;
 using Microsoft.Extensions.Primitives;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
     /// <summary>
     /// <see cref="IModelBinder"/> implementation to bind form values to <see cref="IFormCollection"/>.
@@ -19,27 +18,13 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
     public class FormCollectionModelBinder : IModelBinder
     {
         /// <inheritdoc />
-        public Task BindModelAsync(ModelBindingContext bindingContext)
+        public async Task BindModelAsync(ModelBindingContext bindingContext)
         {
             if (bindingContext == null)
             {
                 throw new ArgumentNullException(nameof(bindingContext));
             }
 
-            // This method is optimized to use cached tasks when possible and avoid allocating
-            // using Task.FromResult. If you need to make changes of this nature, profile
-            // allocations afterwards and look for Task<ModelBindingResult>.
-
-            if (bindingContext.ModelType != typeof(IFormCollection))
-            {
-                return TaskCache.CompletedTask;
-            }
-
-            return BindModelCoreAsync(bindingContext);
-        }
-
-        private async Task BindModelCoreAsync(ModelBindingContext bindingContext)
-        {
             object model;
             var request = bindingContext.OperationBindingContext.HttpContext.Request;
             if (request.HasFormContentType)

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/FormCollectionModelBinderProvider.cs

@@ -0,0 +1,30 @@
+// 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;
+using Microsoft.AspNetCore.Http;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    /// <summary>
+    /// An <see cref="IModelBinderProvider"/> for <see cref="IFormCollection"/>.
+    /// </summary>
+    public class FormCollectionModelBinderProvider : IModelBinderProvider
+    {
+        /// <inheritdoc />
+        public IModelBinder GetBinder(ModelBinderProviderContext context)
+        {
+            if (context == null)
+            {
+                throw new ArgumentNullException(nameof(context));
+            }
+
+            if (context.Metadata.ModelType == typeof(IFormCollection))
+            {
+                return new FormCollectionModelBinder();
+            }
+
+            return null;
+        }
+    }
+}

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/FormFileModelBinder.cs

@@ -11,10 +11,9 @@ using System.Reflection;
 #endif
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http;
-using Microsoft.AspNetCore.Mvc.Internal;
 using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
     /// <summary>
     /// <see cref="IModelBinder"/> implementation to bind posted files to <see cref="IFormFile"/>.
@@ -22,31 +21,22 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
     public class FormFileModelBinder : IModelBinder
     {
         /// <inheritdoc />
-        public Task BindModelAsync(ModelBindingContext bindingContext)
+        public async Task BindModelAsync(ModelBindingContext bindingContext)
         {
             if (bindingContext == null)
             {
                 throw new ArgumentNullException(nameof(bindingContext));
             }
 
-            // This method is optimized to use cached tasks when possible and avoid allocating
+            var createFileCollection = 
-            // using Task.FromResult or async state machines.
+                bindingContext.ModelType == typeof(IFormFileCollection) &&
-
-            var modelType = bindingContext.ModelType;
-            if (modelType != typeof(IFormFile) && !typeof(IEnumerable<IFormFile>).IsAssignableFrom(modelType))
-            {
-                // Not a type this model binder supports. Let other binders run.
-                return TaskCache.CompletedTask;
-            }
-
-            var createFileCollection = modelType == typeof(IFormFileCollection) &&
                 !bindingContext.ModelMetadata.IsReadOnly;
             if (!createFileCollection && !ModelBindingHelper.CanGetCompatibleCollection<IFormFile>(bindingContext))
             {
                 // Silently fail and stop other model binders running if unable to create an instance or use the
                 // current instance.
                 bindingContext.Result = ModelBindingResult.Failed(bindingContext.ModelName);
-                return TaskCache.CompletedTask;
+                return;
             }
 
             ICollection<IFormFile> postedFiles;
@@ -59,13 +49,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 postedFiles = ModelBindingHelper.GetCompatibleCollection<IFormFile>(bindingContext);
             }
 
-            return BindModelCoreAsync(bindingContext, postedFiles);
-        }
-
-        private async Task BindModelCoreAsync(ModelBindingContext bindingContext, ICollection<IFormFile> postedFiles)
-        {
-            Debug.Assert(postedFiles != null);
-
             // If we're at the top level, then use the FieldName (parameter or property name).
             // This handles the fact that there will be nothing in the ValueProviders for this parameter
             // and so we'll do the right thing even though we 'fell-back' to the empty prefix.

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/FormFileModelBinderProvider.cs

@@ -0,0 +1,36 @@
+// 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;
+using System.Collections.Generic;
+using System.Reflection;
+using Microsoft.AspNetCore.Http;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    /// <summary>
+    /// An <see cref="IModelBinderProvider"/> for <see cref="IFormFile"/>, collections
+    /// of <see cref="IFormFile"/>, and <see cref="IFormFileCollection"/>.
+    /// </summary>
+    public class FormFileModelBinderProvider : IModelBinderProvider
+    {
+        /// <inheritdoc />
+        public IModelBinder GetBinder(ModelBinderProviderContext context)
+        {
+            if (context == null)
+            {
+                throw new ArgumentNullException(nameof(context));
+            }
+
+            var modelType = context.Metadata.ModelType;
+            if (modelType == typeof(IFormFile) ||
+                modelType == typeof(IFormFileCollection) ||
+                typeof(IEnumerable<IFormFile>).GetTypeInfo().IsAssignableFrom(modelType.GetTypeInfo()))
+            {
+                return new FormFileModelBinder();
+            }
+
+            return null;
+        }
+    }
+}

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/HeaderModelBinder.cs

@@ -9,7 +9,7 @@ using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc.Internal;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
     /// <summary>
     /// An <see cref="IModelBinder"/> which binds models from the request headers when a model
@@ -25,36 +25,21 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 throw new ArgumentNullException(nameof(bindingContext));
             }
 
-            // This method is optimized to use cached tasks when possible and avoid allocating
-            // using Task.FromResult or async state machines.
-
-            var allowedBindingSource = bindingContext.BindingSource;
-            if (allowedBindingSource == null ||
-                !allowedBindingSource.CanAcceptDataFrom(BindingSource.Header))
-            {
-                // Headers are opt-in. This model either didn't specify [FromHeader] or specified something
-                // incompatible so let other binders run.
-                return TaskCache.CompletedTask;
-            }
-
             var request = bindingContext.OperationBindingContext.HttpContext.Request;
 
             // Property name can be null if the model metadata represents a type (rather than a property or parameter).
             var headerName = bindingContext.FieldName;
 
             object model;
-            if (ModelBindingHelper.CanGetCompatibleCollection<string>(bindingContext))
+            if (bindingContext.ModelType == typeof(string))
             {
-                if (bindingContext.ModelType == typeof(string))
+                var value = request.Headers[headerName];
-                {
+                model = (string)value;
-                    var value = request.Headers[headerName];
+            }
-                    model = (string)value;
+            else if (ModelBindingHelper.CanGetCompatibleCollection<string>(bindingContext))
-                }
+            {
-                else
+                var values = request.Headers.GetCommaSeparatedValues(headerName);
-                {
+                model = GetCompatibleCollection(bindingContext, values);
-                    var values = request.Headers.GetCommaSeparatedValues(headerName);
-                    model = GetCompatibleCollection(bindingContext, values);
-                }
             }
             else
             {

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/HeaderModelBinderProvider.cs

@@ -0,0 +1,36 @@
+// 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;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    /// <summary>
+    /// An <see cref="IModelBinderProvider"/> for binding header values.
+    /// </summary>
+    public class HeaderModelBinderProvider : IModelBinderProvider
+    {
+        /// <inheritdoc />
+        public IModelBinder GetBinder(ModelBinderProviderContext context)
+        {
+            if (context == null)
+            {
+                throw new ArgumentNullException(nameof(context));
+            }
+
+            if (context.BindingInfo?.BindingSource != null &&
+                context.BindingInfo.BindingSource.CanAcceptDataFrom(BindingSource.Header))
+            {
+                // We only support strings and collections of strings. Some cases can fail
+                // at runtime due to collections we can't modify.
+                if (context.Metadata.ModelType == typeof(string) ||
+                    context.Metadata.ElementType == typeof(string))
+                {
+                    return new HeaderModelBinder();
+                }
+            }
+
+            return null;
+        }
+    }
+}

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/KeyValuePairModelBinder.cs

@@ -5,10 +5,40 @@ using System;
 using System.Collections.Generic;
 using System.Threading.Tasks;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
-    public sealed class KeyValuePairModelBinder<TKey, TValue> : IModelBinder
+    /// <summary>
+    /// An <see cref="IModelBinder"/> for <see cref="KeyValuePair{TKey, TValue}"/>.
+    /// </summary>
+    /// <typeparam name="TKey">The key type.</typeparam>
+    /// <typeparam name="TValue">The value type.</typeparam>
+    public class KeyValuePairModelBinder<TKey, TValue> : IModelBinder
     {
+        private readonly IModelBinder _keyBinder;
+        private readonly IModelBinder _valueBinder;
+
+        /// <summary>
+        /// Creates a new <see cref="KeyValuePair{TKey, TValue}"/>.
+        /// </summary>
+        /// <param name="keyBinder">The <see cref="IModelBinder"/> for <typeparamref name="TKey"/>.</param>
+        /// <param name="valueBinder">The <see cref="IModelBinder"/> for <typeparamref name="TValue"/>.</param>
+        public KeyValuePairModelBinder(IModelBinder keyBinder, IModelBinder valueBinder)
+        {
+            if (keyBinder == null)
+            {
+                throw new ArgumentNullException(nameof(keyBinder));
+            }
+
+            if (valueBinder == null)
+            {
+                throw new ArgumentNullException(nameof(valueBinder));
+            }
+
+            _keyBinder = keyBinder;
+            _valueBinder = valueBinder;
+        }
+
+        /// <inheritdoc />
         public async Task BindModelAsync(ModelBindingContext bindingContext)
         {
             if (bindingContext == null)
@@ -16,14 +46,8 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 throw new ArgumentNullException(nameof(bindingContext));
             }
 
-            if (bindingContext.ModelType != typeof(KeyValuePair<TKey, TValue>))
+            var keyResult = await TryBindStrongModel<TKey>(bindingContext, _keyBinder, "Key");
-            {
+            var valueResult = await TryBindStrongModel<TValue>(bindingContext, _valueBinder, "Value");
-                // This binder does not apply.
-                return;
-            }
-
-            var keyResult = await TryBindStrongModel<TKey>(bindingContext, "Key");
-            var valueResult = await TryBindStrongModel<TValue>(bindingContext, "Value");
 
             if (keyResult.IsModelSet && valueResult.IsModelSet)
             {
@@ -70,6 +94,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
 
         internal async Task<ModelBindingResult> TryBindStrongModel<TModel>(
             ModelBindingContext bindingContext,
+            IModelBinder binder,
             string propertyName)
         {
             var propertyModelMetadata =
@@ -83,9 +108,8 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 modelName: propertyModelName,
                 model: null))
             {
+                await binder.BindModelAsync(bindingContext);
 
-                await bindingContext.OperationBindingContext.ModelBinder.BindModelAsync(
-                    bindingContext);
                 var result = bindingContext.Result;
                 if (result != null && result.Value.IsModelSet)
                 {

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/KeyValuePairModelBinderProvider.cs

@@ -0,0 +1,42 @@
+// 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;
+using System.Collections.Generic;
+using System.Reflection;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    /// <summary>
+    /// An <see cref="IModelBinderProvider"/> for <see cref="KeyValuePair{TKey, TValue}"/>.
+    /// </summary>
+    public class KeyValuePairModelBinderProvider : IModelBinderProvider
+    {
+        /// <inheritdoc />
+        public IModelBinder GetBinder(ModelBinderProviderContext context)
+        {
+            if (context == null)
+            {
+                throw new ArgumentNullException(nameof(context));
+            }
+
+            var modelTypeInfo = context.Metadata.ModelType.GetTypeInfo();
+            if (modelTypeInfo.IsGenericType && 
+                modelTypeInfo.GetGenericTypeDefinition().GetTypeInfo() == typeof(KeyValuePair<,>).GetTypeInfo())
+            {
+                var typeArguments = modelTypeInfo.GenericTypeArguments;
+
+                var keyMetadata = context.MetadataProvider.GetMetadataForType(typeArguments[0]);
+                var keyBinder = context.CreateBinder(keyMetadata);
+
+                var valueMetadata = context.MetadataProvider.GetMetadataForType(typeArguments[1]);
+                var valueBinder = context.CreateBinder(valueMetadata);
+
+                var binderType = typeof(KeyValuePairModelBinder<,>).MakeGenericType(typeArguments);
+                return (IModelBinder)Activator.CreateInstance(binderType, keyBinder, valueBinder);
+            }
+
+            return null;
+        }
+    }
+}

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/ServicesModelBinder.cs

@@ -2,13 +2,12 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.Diagnostics;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Mvc.Internal;
 using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;
 using Microsoft.Extensions.DependencyInjection;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
     /// <summary>
     /// An <see cref="IModelBinder"/> which binds models from the request services when a model 
@@ -24,19 +23,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 throw new ArgumentNullException(nameof(bindingContext));
             }
 
-            // This method is optimized to use cached tasks when possible and avoid allocating
-            // using Task.FromResult. If you need to make changes of this nature, profile
-            // allocations afterwards and look for Task<ModelBindingResult>.
-
-            var allowedBindingSource = bindingContext.BindingSource;
-            if (allowedBindingSource == null ||
-                !allowedBindingSource.CanAcceptDataFrom(BindingSource.Services))
-            {
-                // Services are opt-in. This model either didn't specify [FromService] or specified something
-                // incompatible so let other binders run.
-                return TaskCache.CompletedTask;
-            }
-
             var requestServices = bindingContext.OperationBindingContext.HttpContext.RequestServices;
             var model = requestServices.GetRequiredService(bindingContext.ModelType);
 

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/ServicesModelBinderProvider.cs

@@ -0,0 +1,30 @@
+// 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;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    /// <summary>
+    /// An <see cref="IModelBinderProvider"/> for binding from the <see cref="IServiceProvider"/>.
+    /// </summary>
+    public class ServicesModelBinderProvider : IModelBinderProvider
+    {
+        /// <inheritdoc />
+        public IModelBinder GetBinder(ModelBinderProviderContext context)
+        {
+            if (context == null)
+            {
+                throw new ArgumentNullException(nameof(context));
+            }
+
+            if (context.BindingInfo?.BindingSource != null &&
+                context.BindingInfo.BindingSource.CanAcceptDataFrom(BindingSource.Services))
+            {
+                return new ServicesModelBinder();
+            }
+
+            return null;
+        }
+    }
+}

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/SimpleTypeModelBinder.cs

@@ -5,10 +5,14 @@ using System;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Mvc.Internal;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
+    /// <summary>
+    /// An <see cref="IModelBinder"/> for simple types.
+    /// </summary>
     public class SimpleTypeModelBinder : IModelBinder
     {
+        /// <inheritdoc />
         public Task BindModelAsync(ModelBindingContext bindingContext)
         {
             if (bindingContext == null)
@@ -16,20 +20,11 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 throw new ArgumentNullException(nameof(bindingContext));
             }
 
-            // This method is optimized to use cached tasks when possible and avoid allocating
-            // using Task.FromResult. If you need to make changes of this nature, profile
-            // allocations afterwards and look for Task<ModelBindingResult>.
-
-            if (bindingContext.ModelMetadata.IsComplexType)
-            {
-                // this type cannot be converted
-                return TaskCache.CompletedTask;
-            }
-
             var valueProviderResult = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);
             if (valueProviderResult == ValueProviderResult.None)
             {
                 // no entry
+                bindingContext.Result = ModelBindingResult.Failed(bindingContext.ModelName);
                 return TaskCache.CompletedTask;
             }
 

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/SimpleTypeModelBinderProvider.cs

@@ -0,0 +1,29 @@
+// 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;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    /// <summary>
+    /// An <see cref="IModelBinderProvider"/> for binding simple data types.
+    /// </summary>
+    public class SimpleTypeModelBinderProvider : IModelBinderProvider
+    {
+        /// <inheritdoc />
+        public IModelBinder GetBinder(ModelBinderProviderContext context)
+        {
+            if (context == null)
+            {
+                throw new ArgumentNullException(nameof(context));
+            }
+
+            if (!context.Metadata.IsComplexType)
+            {
+                return new SimpleTypeModelBinder();
+            }
+
+            return null;
+        }
+    }
+}

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

@@ -1,171 +0,0 @@
-// 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;
-using System.Collections.Generic;
-using System.Runtime.CompilerServices;
-using System.Threading.Tasks;
-using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;
-
-namespace Microsoft.AspNetCore.Mvc.ModelBinding
-{
-    /// <summary>
-    /// Represents an <see cref="IModelBinder"/> that delegates to one of a collection of <see cref="IModelBinder"/>
-    /// instances.
-    /// </summary>
-    /// <remarks>
-    /// If no binder is available and the <see cref="ModelBindingContext"/> allows it,
-    /// this class tries to find a binder using an empty prefix.
-    /// </remarks>
-    public class CompositeModelBinder : ICompositeModelBinder
-    {
-        /// <summary>
-        /// Initializes a new instance of the CompositeModelBinder class.
-        /// </summary>
-        /// <param name="modelBinders">A collection of <see cref="IModelBinder"/> instances.</param>
-        public CompositeModelBinder(IList<IModelBinder> modelBinders)
-        {
-            if (modelBinders == null)
-            {
-                throw new ArgumentNullException(nameof(modelBinders));
-            }
-
-            ModelBinders = modelBinders;
-        }
-
-        /// <inheritdoc />
-        public IList<IModelBinder> ModelBinders { get; }
-
-        public virtual Task BindModelAsync(ModelBindingContext bindingContext)
-        {
-            if (bindingContext == null)
-            {
-                throw new ArgumentNullException(nameof(bindingContext));
-            }
-
-            return RunModelBinders(bindingContext);
-        }
-
-        private async Task RunModelBinders(ModelBindingContext bindingContext)
-        {
-            RuntimeHelpers.EnsureSufficientExecutionStack();
-
-            ModelBindingResult? overallResult = null;
-            try
-            {
-                using (bindingContext.EnterNestedScope())
-                {
-                    if (PrepareBindingContext(bindingContext))
-                    {
-                        // Perf: Avoid allocations
-                        for (var i = 0; i < ModelBinders.Count; i++)
-                        {
-                            var binder = ModelBinders[i];
-                            await binder.BindModelAsync(bindingContext);
-                            if (bindingContext.Result != null)
-                            {
-                                var result = bindingContext.Result.Value;
-                                // This 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.IsModelSet ||
-                                    bindingContext.ModelState.ContainsKey(bindingContext.ModelName))
-                                {
-                                    if (bindingContext.IsTopLevelObject && result.Model != null)
-                                    {
-                                        ValidationStateEntry entry;
-                                        if (!bindingContext.ValidationState.TryGetValue(result.Model, out entry))
-                                        {
-                                            entry = new ValidationStateEntry()
-                                            {
-                                                Key = result.Key,
-                                                Metadata = bindingContext.ModelMetadata,
-                                            };
-                                            bindingContext.ValidationState.Add(result.Model, entry);
-                                        }
-                                    }
-
-                                    overallResult = bindingContext.Result;
-                                    return;
-                                }
-
-                                // Current binder should have been able to bind value but found nothing. Exit loop in a way that
-                                // tells caller to fall back to the empty prefix, if appropriate. Do not return result because it
-                                // means only "other binders are not applicable".
-
-                                // overallResult MUST still be null at this return statement.
-                                return;
-                            }
-                        }
-                    }
-                }
-            }
-            finally
-            {
-                bindingContext.Result = overallResult;
-            }
-        }
-
-        private static bool PrepareBindingContext(ModelBindingContext bindingContext)
-        {
-            // If the property has a specified data binding sources, we need to filter the set of value providers
-            // to just those that match. We can skip filtering when IsGreedy == true, because that can't use
-            // value providers.
-            //
-            // We also want to base this filtering on the - top-level value provider in case the data source
-            // on this property doesn't intersect with the ambient data source.
-            //
-            // Ex:
-            //
-            // public class Person
-            // {
-            //      [FromQuery]
-            //      public int Id { get; set; }
-            // }
-            //
-            // public IActionResult UpdatePerson([FromForm] Person person) { }
-            //
-            // In this example, [FromQuery] overrides the ambient data source (form).
-
-            var valueProvider = bindingContext.ValueProvider;
-            var bindingSource = bindingContext.BindingSource;
-            var modelName = bindingContext.ModelName;
-            var fallbackToEmptyPrefix = bindingContext.FallbackToEmptyPrefix;
-
-            if (bindingSource != null && !bindingSource.IsGreedy)
-            {
-                var bindingSourceValueProvider = valueProvider as IBindingSourceValueProvider;
-                if (bindingSourceValueProvider != null)
-                {
-                    valueProvider = bindingSourceValueProvider.Filter(bindingSource);
-                    if (valueProvider == null)
-                    {
-                        // Unable to find a value provider for this binding source.
-                        return false;
-                    }
-                }
-            }
-
-            if (bindingSource != null && bindingSource.IsGreedy)
-            {
-                bindingContext.ModelName = modelName;
-            }
-            else if (
-                !fallbackToEmptyPrefix ||
-                valueProvider.ContainsPrefix(bindingContext.ModelName))
-            {
-                bindingContext.ModelName = modelName;
-            }
-            else
-            {
-                bindingContext.ModelName = string.Empty;
-            }
-
-            bindingContext.ValueProvider = valueProvider;
-            bindingContext.FallbackToEmptyPrefix = false;
-
-            return true;
-        }
-    }
-}

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

@@ -1,175 +0,0 @@
-// 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;
-using System.Collections.Generic;
-using System.Diagnostics;
-#if NETSTANDARD1_5
-using System.Reflection;
-#endif
-using System.Threading.Tasks;
-using Microsoft.AspNetCore.Mvc.Internal;
-using Microsoft.Extensions.Internal;
-
-namespace Microsoft.AspNetCore.Mvc.ModelBinding
-{
-    public class GenericModelBinder : IModelBinder
-    {
-        public Task BindModelAsync(ModelBindingContext bindingContext)
-        {
-            if (bindingContext == null)
-            {
-                throw new ArgumentNullException(nameof(bindingContext));
-            }
-
-            // This method is optimized to use cached tasks when possible and avoid allocating
-            // using Task.FromResult. If you need to make changes of this nature, profile
-            // allocations afterwards and look for Task<ModelBindingResult>.
-
-            var binderType = ResolveBinderType(bindingContext);
-            if (binderType == null)
-            {
-                return TaskCache.CompletedTask;
-            }
-
-            var binder = (IModelBinder)Activator.CreateInstance(binderType);
-
-            var collectionBinder = binder as ICollectionModelBinder;
-            if (collectionBinder != null &&
-                bindingContext.Model == null &&
-                !collectionBinder.CanCreateInstance(bindingContext.ModelType))
-            {
-                // Able to resolve a binder type but need a new model instance and that binder cannot create it.
-                return TaskCache.CompletedTask;
-            }
-
-            return BindModelCoreAsync(bindingContext, binder);
-        }
-
-        private async Task BindModelCoreAsync(ModelBindingContext bindingContext, IModelBinder binder)
-        {
-            Debug.Assert(binder != null);
-
-            await binder.BindModelAsync(bindingContext);
-            if (bindingContext.Result == null)
-            {
-                // Always tell the model binding system to skip other model binders.
-                bindingContext.Result = ModelBindingResult.Failed(bindingContext.ModelName);
-            }
-        }
-
-        private static Type ResolveBinderType(ModelBindingContext context)
-        {
-            var modelType = context.ModelType;
-
-            return GetArrayBinder(modelType) ??
-                GetDictionaryBinder(modelType) ??
-                GetCollectionBinder(modelType) ??
-                GetEnumerableBinder(context) ??
-                GetKeyValuePairBinder(modelType);
-        }
-
-        private static Type GetArrayBinder(Type modelType)
-        {
-            if (modelType.IsArray)
-            {
-                var elementType = modelType.GetElementType();
-                return typeof(ArrayModelBinder<>).MakeGenericType(elementType);
-            }
-
-            return null;
-        }
-
-        private static Type GetCollectionBinder(Type modelType)
-        {
-            return GetGenericBinderType(
-                typeof(ICollection<>),
-                typeof(CollectionModelBinder<>),
-                modelType);
-        }
-
-        private static Type GetDictionaryBinder(Type modelType)
-        {
-            return GetGenericBinderType(
-                typeof(IDictionary<,>),
-                typeof(DictionaryModelBinder<,>),
-                modelType);
-        }
-
-        private static Type GetEnumerableBinder(ModelBindingContext context)
-        {
-            var modelTypeArguments = GetGenericBinderTypeArgs(typeof(IEnumerable<>), context.ModelType);
-            if (modelTypeArguments == null)
-            {
-                return null;
-            }
-
-            if (context.Model == null)
-            {
-                // GetCollectionBinder has already confirmed modelType is not compatible with ICollection<T>. Can a
-                // List<T> (the default CollectionModelBinder type) instance be used instead of that exact type?
-                // Likely this will succeed only if the property type is exactly IEnumerable<T>.
-                var closedListType = typeof(List<>).MakeGenericType(modelTypeArguments);
-                if (!context.ModelType.IsAssignableFrom(closedListType))
-                {
-                    return null;
-                }
-            }
-            else
-            {
-                // A non-null instance must be updated in-place. For that the instance must also implement
-                // ICollection<T>. For example an IEnumerable<T> property may have a List<T> default value. Do not use
-                // IsAssignableFrom() because that does not handle explicit interface implementations and binders all
-                // perform explicit casts.
-                if (!context.ModelMetadata.IsCollectionType)
-                {
-                    return null;
-                }
-            }
-
-            return typeof(CollectionModelBinder<>).MakeGenericType(modelTypeArguments);
-        }
-
-        private static Type GetKeyValuePairBinder(Type modelType)
-        {
-            Debug.Assert(modelType != null);
-
-            // Since KeyValuePair is a value type, ExtractGenericInterface() succeeds only on an exact match.
-            var closedGenericType = ClosedGenericMatcher.ExtractGenericInterface(modelType, typeof(KeyValuePair<,>));
-            if (closedGenericType != null)
-            {
-                return typeof(KeyValuePairModelBinder<,>).MakeGenericType(modelType.GenericTypeArguments);
-            }
-
-            return null;
-        }
-
-        // Example: GetGenericBinderType(typeof(IList<T>), typeof(ListBinder<T>), ...) means that the ListBinder<T>
-        // type can update models that implement IList<T>. This method will return
-        // ListBinder<T> or null, depending on whether the type checks succeed.
-        private static Type GetGenericBinderType(Type supportedInterfaceType, Type openBinderType, Type modelType)
-        {
-            Debug.Assert(openBinderType != null);
-
-            var modelTypeArguments = GetGenericBinderTypeArgs(supportedInterfaceType, modelType);
-            if (modelTypeArguments == null)
-            {
-                return null;
-            }
-
-            return openBinderType.MakeGenericType(modelTypeArguments);
-        }
-
-        // Get the generic arguments for the binder, based on the model type. Or null if not compatible.
-        private static Type[] GetGenericBinderTypeArgs(Type supportedInterfaceType, Type modelType)
-        {
-            Debug.Assert(supportedInterfaceType != null);
-            Debug.Assert(modelType != null);
-
-            var closedGenericInterface =
-                ClosedGenericMatcher.ExtractGenericInterface(modelType, supportedInterfaceType);
-
-            return closedGenericInterface?.GenericTypeArguments;
-        }
-    }
-}

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/IModelBinderFactory.cs

@@ -0,0 +1,18 @@
+// 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.
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding
+{
+    /// <summary>
+    /// A factory abstraction for creating <see cref="IModelBinder"/> instances.
+    /// </summary>
+    public interface IModelBinderFactory
+    {
+        /// <summary>
+        /// Creates a new <see cref="IModelBinder"/>.
+        /// </summary>
+        /// <param name="context">The <see cref="ModelBinderFactoryContext"/>.</param>
+        /// <returns>An <see cref="IModelBinder"/> instance.</returns>
+        IModelBinder CreateBinder(ModelBinderFactoryContext context);
+    }
+}

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/ModelBinderFactory.cs

@@ -0,0 +1,233 @@
+// 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;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+using System.Runtime.CompilerServices;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Mvc.Core;
+using Microsoft.AspNetCore.Mvc.Internal;
+using Microsoft.AspNetCore.Mvc.ModelBinding.Internal;
+using Microsoft.Extensions.Internal;
+using Microsoft.Extensions.Options;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding
+{
+    /// <summary>
+    /// A factory for <see cref="IModelBinder"/> instances.
+    /// </summary>
+    public class ModelBinderFactory : IModelBinderFactory
+    {
+        private readonly IModelMetadataProvider _metadataProvider;
+        private readonly IModelBinderProvider[] _providers;
+
+        private readonly ConcurrentDictionary<object, IModelBinder> _cache;
+
+        /// <summary>
+        /// Creates a new <see cref="ModelBinderFactory"/>.
+        /// </summary>
+        /// <param name="metadataProvider">The <see cref="IModelMetadataProvider"/>.</param>
+        /// <param name="options">The <see cref="IOptions{TOptions}"/> for <see cref="MvcOptions"/>.</param>
+        public ModelBinderFactory(IModelMetadataProvider metadataProvider, IOptions<MvcOptions> options)
+        {
+            _metadataProvider = metadataProvider;
+            _providers = options.Value.ModelBinderProviders.ToArray();
+
+            _cache = new ConcurrentDictionary<object, IModelBinder>(ReferenceEqualityComparer.Instance);
+        }
+
+        /// <inheritdoc />
+        public IModelBinder CreateBinder(ModelBinderFactoryContext context)
+        {
+            if (context == null)
+            {
+                throw new ArgumentNullException(nameof(context));
+            }
+
+            // We perform caching in CreateBinder (not in CreateBinderCore) because we only want to
+            // cache the top-level binder.
+            IModelBinder binder;
+            if (context.CacheToken != null && _cache.TryGetValue(context.CacheToken, out binder))
+            {
+                return binder;
+            }
+
+            var providerContext = new DefaultModelBinderProviderContext(this, context);
+            binder = CreateBinderCore(providerContext, context.CacheToken);
+            if (binder == null)
+            {
+                var message = Resources.FormatCouldNotCreateIModelBinder(providerContext.Metadata.ModelType);
+                throw new InvalidOperationException(message);
+            }
+
+            if (context.CacheToken != null)
+            {
+                _cache.TryAdd(context.CacheToken, binder);
+            }
+
+            return binder;
+        }
+
+        private IModelBinder CreateBinderCore(DefaultModelBinderProviderContext providerContext, object token)
+        {
+            // A non-null token will usually be passed in at the the top level (ParameterDescriptor likely).
+            // This prevents us from treating a parameter the same as a collection-element - which could
+            // happen looking at just model metadata.
+            var key = new Key(providerContext.Metadata, token);
+
+            // If we're currently recursively building a binder for this type, just return
+            // a PlaceholderBinder. We'll fix it up later to point to the 'real' binder
+            // when the stack unwinds.
+            var stack = providerContext.Stack;
+            for (var i = 0; i < stack.Count; i++)
+            {
+                var entry = stack[i];
+                if (key.Equals(entry.Key))
+                {
+                    if (entry.Value == null)
+                    {
+                        // Recursion detected, create a DelegatingBinder.
+                        var binder = new PlaceholderBinder();
+                        stack[i] = new KeyValuePair<Key, PlaceholderBinder>(entry.Key, binder);
+                        return binder;
+                    }
+                    else
+                    {
+                        return entry.Value;
+                    }
+                }
+            }
+
+            // OK this isn't a recursive case (yet) so "push" an entry on the stack and then ask the providers
+            // to create the binder.
+            stack.Add(new KeyValuePair<Key, PlaceholderBinder>(key, null));
+
+            IModelBinder result = null;
+
+            for (var i = 0; i < _providers.Length; i++)
+            {
+                var provider = _providers[i];
+                result = provider.GetBinder(providerContext);
+                if (result != null)
+                {
+                    break;
+                }
+            }
+
+            if (result == null && stack.Count > 1)
+            {
+                // Use a no-op binder if we're below the top level. At the top level, we throw.
+                result = NoOpBinder.Instance;
+            }
+
+            // "pop"
+            Debug.Assert(stack.Count > 0);
+            var delegatingBinder = stack[stack.Count - 1].Value;
+            stack.RemoveAt(stack.Count - 1);
+
+            // If the DelegatingBinder was created, then it means we recursed. Hook it up to the 'real' binder.
+            if (delegatingBinder != null)
+            {
+                delegatingBinder.Inner = result;
+            }
+
+            return result;
+        }
+
+        private class DefaultModelBinderProviderContext : ModelBinderProviderContext
+        {
+            private readonly ModelBinderFactory _factory;
+
+            public DefaultModelBinderProviderContext(
+                ModelBinderFactory factory,
+                ModelBinderFactoryContext factoryContext)
+            {
+                _factory = factory;
+                Metadata = factoryContext.Metadata;
+                BindingInfo = factoryContext.BindingInfo;
+
+                MetadataProvider = _factory._metadataProvider;
+                Stack = new List<KeyValuePair<Key, PlaceholderBinder>>();
+            }
+
+            private DefaultModelBinderProviderContext(
+                DefaultModelBinderProviderContext parent,
+                ModelMetadata metadata)
+            {
+                Metadata = metadata;
+
+                _factory = parent._factory;
+                MetadataProvider = parent.MetadataProvider;
+                Stack = parent.Stack;
+
+                BindingInfo = new BindingInfo()
+                {
+                    BinderModelName = metadata.BinderModelName,
+                    BinderType = metadata.BinderType,
+                    BindingSource = metadata.BindingSource,
+                    PropertyBindingPredicateProvider = metadata.PropertyBindingPredicateProvider,
+                };
+            }
+
+            public override BindingInfo BindingInfo { get; }
+
+            public override ModelMetadata Metadata { get; }
+
+            public override IModelMetadataProvider MetadataProvider { get; }
+
+            // Not using a 'real' Stack<> because we want random access to modify the entries.
+            public List<KeyValuePair<Key, PlaceholderBinder>> Stack { get; }
+
+            public override IModelBinder CreateBinder(ModelMetadata metadata)
+            {
+                var nestedContext = new DefaultModelBinderProviderContext(this, metadata);
+                return _factory.CreateBinderCore(nestedContext, token: null);
+            }
+        }
+
+        private class NoOpBinder : IModelBinder
+        {
+            public static readonly IModelBinder Instance = new NoOpBinder();
+
+            public Task BindModelAsync(ModelBindingContext bindingContext)
+            {
+                bindingContext.Result = ModelBindingResult.Failed(bindingContext.ModelName);
+                return TaskCache.CompletedTask;
+            }
+        }
+
+        private struct Key : IEquatable<Key>
+        {
+            private readonly ModelMetadata _metadata;
+            private readonly object _token; // Explicitly using ReferenceEquality for tokens.
+
+            public Key(ModelMetadata metadata, object token)
+            {
+                _metadata = metadata;
+                _token = token;
+            }
+
+            public bool Equals(Key other)
+            {
+                return _metadata.Equals(other._metadata) && object.ReferenceEquals(_token, other._token);
+            }
+
+            public override bool Equals(object obj)
+            {
+                var other = obj as Key?;
+                return other.HasValue && Equals(other.Value);
+            }
+
+            public override int GetHashCode()
+            {
+                var hash = new HashCodeCombiner();
+                hash.Add(_metadata);
+                hash.Add(RuntimeHelpers.GetHashCode(_token));
+                return hash;
+            }
+        }
+    }
+}

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/ModelBinderFactoryContext.cs

@@ -0,0 +1,27 @@
+// 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.
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding
+{
+    /// <summary>
+    /// A context object for <see cref="ModelBinderFactory.CreateBinder"/>.
+    /// </summary>
+    public class ModelBinderFactoryContext
+    {
+        /// <summary>
+        /// Gets or sets the <see cref="ModelBinding.BindingInfo"/>.
+        /// </summary>
+        public BindingInfo BindingInfo { get; set; }
+
+        /// <summary>
+        /// Gets or sets the <see cref="ModelMetadata"/>.
+        /// </summary>
+        public ModelMetadata Metadata { get; set; }
+
+        /// <summary>
+        /// Gets or sets the cache token. If <c>non-null</c> the resulting <see cref="IModelBinder"/>
+        /// will be cached.
+        /// </summary>
+        public object CacheToken { get; set; }
+    }
+}

src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/ModelBindingHelper.cs

@@ -20,9 +20,9 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
     public static class ModelBindingHelper
     {
         /// <summary>
-        /// Updates the specified <paramref name="model"/> instance using the specified <paramref name="modelBinder"/>
+        /// Updates the specified <paramref name="model"/> instance using the specified
-        /// and the specified <paramref name="valueProvider"/> and executes validation using the specified
+        /// <paramref name="modelBinderFactory"/> and the specified <paramref name="valueProvider"/> and executes 
-        /// <paramref name="validatorProvider"/>.
+        /// validation using the specified <paramref name="validatorProvider"/>.
         /// </summary>
         /// <typeparam name="TModel">The type of the model object.</typeparam>
         /// <param name="model">The model instance to update and validate.</param>
@@ -30,7 +30,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         /// </param>
         /// <param name="actionContext">The <see cref="ActionContext"/> for the current executing request.</param>
         /// <param name="metadataProvider">The provider used for reading metadata for the model type.</param>
-        /// <param name="modelBinder">The <see cref="IModelBinder"/> used for binding.</param>
+        /// <param name="modelBinderFactory">The <see cref="IModelBinderFactory"/> used for binding.</param>
         /// <param name="valueProvider">The <see cref="IValueProvider"/> used for looking up values.</param>
         /// <param name="inputFormatters">
         /// The set of <see cref="IInputFormatter"/> instances for deserializing the body.
@@ -45,7 +45,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             string prefix,
             ActionContext actionContext,
             IModelMetadataProvider metadataProvider,
-            IModelBinder modelBinder,
+            IModelBinderFactory modelBinderFactory,
             IValueProvider valueProvider,
             IList<IInputFormatter> inputFormatters,
             IObjectModelValidator objectModelValidator,
@@ -72,9 +72,9 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 throw new ArgumentNullException(nameof(metadataProvider));
             }
 
-            if (modelBinder == null)
+            if (modelBinderFactory == null)
             {
-                throw new ArgumentNullException(nameof(modelBinder));
+                throw new ArgumentNullException(nameof(modelBinderFactory));
             }
 
             if (valueProvider == null)
@@ -103,7 +103,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 prefix,
                 actionContext,
                 metadataProvider,
-                modelBinder,
+                modelBinderFactory,
                 valueProvider,
                 inputFormatters,
                 objectModelValidator,
@@ -112,7 +112,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         }
 
         /// <summary>
-        /// Updates the specified <paramref name="model"/> instance using the specified <paramref name="modelBinder"/>
+        /// Updates the specified <paramref name="model"/> instance using the specified <paramref name="modelBinderFactory"/>
         /// and the specified <paramref name="valueProvider"/> and executes validation using the specified
         /// <paramref name="validatorProvider"/>.
         /// </summary>
@@ -122,7 +122,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         /// </param>
         /// <param name="actionContext">The <see cref="ActionContext"/> for the current executing request.</param>
         /// <param name="metadataProvider">The provider used for reading metadata for the model type.</param>
-        /// <param name="modelBinder">The <see cref="IModelBinder"/> used for binding.</param>
+        /// <param name="modelBinderFactory">The <see cref="IModelBinderFactory"/> used for binding.</param>
         /// <param name="valueProvider">The <see cref="IValueProvider"/> used for looking up values.</param>
         /// <param name="inputFormatters">
         /// The set of <see cref="IInputFormatter"/> instances for deserializing the body.
@@ -140,7 +140,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             string prefix,
             ActionContext actionContext,
             IModelMetadataProvider metadataProvider,
-            IModelBinder modelBinder,
+            IModelBinderFactory modelBinderFactory,
             IValueProvider valueProvider,
             IList<IInputFormatter> inputFormatters,
             IObjectModelValidator objectModelValidator,
@@ -168,9 +168,9 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 throw new ArgumentNullException(nameof(metadataProvider));
             }
 
-            if (modelBinder == null)
+            if (modelBinderFactory == null)
             {
-                throw new ArgumentNullException(nameof(modelBinder));
+                throw new ArgumentNullException(nameof(modelBinderFactory));
             }
 
             if (valueProvider == null)
@@ -206,7 +206,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                prefix,
                actionContext,
                metadataProvider,
-               modelBinder,
+               modelBinderFactory,
                valueProvider,
                inputFormatters,
                objectModelValidator,
@@ -215,7 +215,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         }
 
         /// <summary>
-        /// Updates the specified <paramref name="model"/> instance using the specified <paramref name="modelBinder"/>
+        /// Updates the specified <paramref name="model"/> instance using the specified <paramref name="modelBinderFactory"/>
         /// and the specified <paramref name="valueProvider"/> and executes validation using the specified
         /// <paramref name="validatorProvider"/>.
         /// </summary>
@@ -225,7 +225,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         /// </param>
         /// <param name="actionContext">The <see cref="ActionContext"/> for the current executing request.</param>
         /// <param name="metadataProvider">The provider used for reading metadata for the model type.</param>
-        /// <param name="modelBinder">The <see cref="IModelBinder"/> used for binding.</param>
+        /// <param name="modelBinderFactory">The <see cref="IModelBinderFactory"/> used for binding.</param>
         /// <param name="valueProvider">The <see cref="IValueProvider"/> used for looking up values.</param>
         /// <param name="inputFormatters">
         /// The set of <see cref="IInputFormatter"/> instances for deserializing the body.
@@ -242,7 +242,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             string prefix,
             ActionContext actionContext,
             IModelMetadataProvider metadataProvider,
-            IModelBinder modelBinder,
+            IModelBinderFactory modelBinderFactory,
             IValueProvider valueProvider,
             IList<IInputFormatter> inputFormatters,
             IObjectModelValidator objectModelValidator,
@@ -270,9 +270,9 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 throw new ArgumentNullException(nameof(metadataProvider));
             }
 
-            if (modelBinder == null)
+            if (modelBinderFactory == null)
             {
-                throw new ArgumentNullException(nameof(modelBinder));
+                throw new ArgumentNullException(nameof(modelBinderFactory));
             }
 
             if (valueProvider == null)
@@ -306,7 +306,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                prefix,
                actionContext,
                metadataProvider,
-               modelBinder,
+               modelBinderFactory,
                valueProvider,
                inputFormatters,
                objectModelValidator,
@@ -315,7 +315,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         }
 
         /// <summary>
-        /// Updates the specified <paramref name="model"/> instance using the specified <paramref name="modelBinder"/>
+        /// Updates the specified <paramref name="model"/> instance using the specified <paramref name="modelBinderFactory"/>
         /// and the specified <paramref name="valueProvider"/> and executes validation using the specified
         /// <paramref name="validatorProvider"/>.
         /// </summary>
@@ -325,7 +325,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         /// </param>
         /// <param name="actionContext">The <see cref="ActionContext"/> for the current executing request.</param>
         /// <param name="metadataProvider">The provider used for reading metadata for the model type.</param>
-        /// <param name="modelBinder">The <see cref="IModelBinder"/> used for binding.</param>
+        /// <param name="modelBinderFactory">The <see cref="IModelBinderFactory"/> used for binding.</param>
         /// <param name="valueProvider">The <see cref="IValueProvider"/> used for looking up values.</param>
         /// <param name="inputFormatters">
         /// The set of <see cref="IInputFormatter"/> instances for deserializing the body.
@@ -341,7 +341,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 string prefix,
                 ActionContext actionContext,
                 IModelMetadataProvider metadataProvider,
-                IModelBinder modelBinder,
+                IModelBinderFactory modelBinderFactory,
                 IValueProvider valueProvider,
                 IList<IInputFormatter> inputFormatters,
                 IObjectModelValidator objectModelValidator,
@@ -372,9 +372,9 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 throw new ArgumentNullException(nameof(metadataProvider));
             }
 
-            if (modelBinder == null)
+            if (modelBinderFactory == null)
             {
-                throw new ArgumentNullException(nameof(modelBinder));
+                throw new ArgumentNullException(nameof(modelBinderFactory));
             }
 
             if (valueProvider == null)
@@ -404,7 +404,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 prefix,
                 actionContext,
                 metadataProvider,
-                modelBinder,
+                modelBinderFactory,
                 valueProvider,
                 inputFormatters,
                 objectModelValidator,
@@ -413,7 +413,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         }
 
         /// <summary>
-        /// Updates the specified <paramref name="model"/> instance using the specified <paramref name="modelBinder"/>
+        /// Updates the specified <paramref name="model"/> instance using the specified <paramref name="modelBinderFactory"/>
         /// and the specified <paramref name="valueProvider"/> and executes validation using the specified
         /// <paramref name="validatorProvider"/>.
         /// </summary>
@@ -423,7 +423,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         /// </param>
         /// <param name="actionContext">The <see cref="ActionContext"/> for the current executing request.</param>
         /// <param name="metadataProvider">The provider used for reading metadata for the model type.</param>
-        /// <param name="modelBinder">The <see cref="IModelBinder"/> used for binding.</param>
+        /// <param name="modelBinderFactory">The <see cref="IModelBinderFactory"/> used for binding.</param>
         /// <param name="valueProvider">The <see cref="IValueProvider"/> used for looking up values.</param>
         /// <param name="inputFormatters">
         /// The set of <see cref="IInputFormatter"/> instances for deserializing the body.
@@ -441,7 +441,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                string prefix,
                ActionContext actionContext,
                IModelMetadataProvider metadataProvider,
-               IModelBinder modelBinder,
+               IModelBinderFactory modelBinderFactory,
                IValueProvider valueProvider,
                IList<IInputFormatter> inputFormatters,
                IObjectModelValidator objectModelValidator,
@@ -473,9 +473,9 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 throw new ArgumentNullException(nameof(metadataProvider));
             }
 
-            if (modelBinder == null)
+            if (modelBinderFactory == null)
             {
-                throw new ArgumentNullException(nameof(modelBinder));
+                throw new ArgumentNullException(nameof(modelBinderFactory));
             }
 
             if (valueProvider == null)
@@ -517,7 +517,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             var operationBindingContext = new OperationBindingContext
             {
                 InputFormatters = inputFormatters,
-                ModelBinder = modelBinder,
                 ValidatorProvider = validatorProvider,
                 MetadataProvider = metadataProvider,
                 ActionContext = actionContext,
@@ -532,7 +531,25 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             modelBindingContext.Model = model;
             modelBindingContext.PropertyFilter = predicate;
 
-            await modelBinder.BindModelAsync(modelBindingContext);
+            var factoryContext = new ModelBinderFactoryContext()
+            {
+                Metadata = modelMetadata,
+                BindingInfo = new BindingInfo()
+                {
+                    BinderModelName = modelMetadata.BinderModelName,
+                    BinderType = modelMetadata.BinderType,
+                    BindingSource = modelMetadata.BindingSource,
+                    PropertyBindingPredicateProvider = modelMetadata.PropertyBindingPredicateProvider,
+                },
+
+                // We're using the model metadata as the cache token here so that TryUpdateModelAsync calls
+                // for the same model type can share a binder. This won't overlap with normal model binding
+                // operations because they use the ParameterDescriptor for the token.
+                CacheToken = modelMetadata,
+            };
+            var binder = modelBinderFactory.CreateBinder(factoryContext);
+
+            await binder.BindModelAsync(modelBindingContext);
             var modelBindingResult = modelBindingContext.Result;
             if (modelBindingResult != null && modelBindingResult.Value.IsModelSet)
             {
@@ -730,19 +747,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             }
         }
 
-        internal static void ValidateBindingContext(ModelBindingContext bindingContext)
-        {
-            if (bindingContext == null)
-            {
-                throw new ArgumentNullException(nameof(bindingContext));
-            }
-
-            if (bindingContext.ModelMetadata == null)
-            {
-                throw new ArgumentException(Resources.ModelBinderUtil_ModelMetadataCannotBeNull, nameof(bindingContext));
-            }
-        }
-
         internal static TModel CastOrDefault<TModel>(object model)
         {
             return (model is TModel) ? (TModel)model : default(TModel);

src/Microsoft.AspNetCore.Mvc.Core/MvcOptions.cs

@@ -27,7 +27,7 @@ namespace Microsoft.AspNetCore.Mvc
             FormatterMappings = new FormatterMappings();
             InputFormatters = new FormatterCollection<IInputFormatter>();
             OutputFormatters = new FormatterCollection<IOutputFormatter>();
-            ModelBinders = new List<IModelBinder>();
+            ModelBinderProviders = new List<IModelBinderProvider>();
             ModelBindingMessageProvider = new ModelBindingMessageProvider();
             ModelMetadataDetailsProviders = new List<IMetadataDetailsProvider>();
             ModelValidatorProviders = new List<IModelValidatorProvider>();
@@ -81,9 +81,9 @@ namespace Microsoft.AspNetCore.Mvc
         }
 
         /// <summary>
-        /// Gets a list of <see cref="IModelBinder"/>s used by this application.
+        /// Gets a list of <see cref="IModelBinderProvider"/>s used by this application.
         /// </summary>
-        public IList<IModelBinder> ModelBinders { get; }
+        public IList<IModelBinderProvider> ModelBinderProviders { get; }
 
         /// <summary>
         /// Gets the default <see cref="IModelBindingMessageProvider"/>. Changes here are copied to the

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

@@ -1162,6 +1162,22 @@ namespace Microsoft.AspNetCore.Mvc.Core
             return string.Format(CultureInfo.CurrentCulture, GetString("MustSpecifyAtLeastOneAuthenticationScheme"));
         }
 
+        /// <summary>
+        /// Could not create a model binder for model object of type '{0}'.
+        /// </summary>
+        internal static string CouldNotCreateIModelBinder
+        {
+            get { return GetString("CouldNotCreateIModelBinder"); }
+        }
+
+        /// <summary>
+        /// Could not create a model binder for model object of type '{0}'.
+        /// </summary>
+        internal static string FormatCouldNotCreateIModelBinder(object p0)
+        {
+            return string.Format(CultureInfo.CurrentCulture, GetString("CouldNotCreateIModelBinder"), p0);
+        }
+
         private static string GetString(string name, params string[] formatterNames)
         {
             var value = _resourceManager.GetString(name);

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

@@ -343,4 +343,7 @@
   <data name="MustSpecifyAtLeastOneAuthenticationScheme" xml:space="preserve">
     <value>At least one authentication scheme must be specified.</value>
   </data>
+  <data name="CouldNotCreateIModelBinder" xml:space="preserve">
+    <value>Could not create a model binder for model object of type '{0}'.</value>
+  </data>
 </root>

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

@@ -17,12 +17,9 @@ namespace Microsoft.AspNetCore.Mvc.WebApiCompatShim
         /// <inheritdoc />
         public Task BindModelAsync(ModelBindingContext bindingContext)
         {
-            if (bindingContext.ModelType == typeof(HttpRequestMessage))
+            var model = bindingContext.OperationBindingContext.HttpContext.GetHttpRequestMessage();
-            {
+            bindingContext.ValidationState.Add(model, new ValidationStateEntry() { SuppressValidation = true });
-                var model = bindingContext.OperationBindingContext.HttpContext.GetHttpRequestMessage();
+            bindingContext.Result = ModelBindingResult.Success(bindingContext.ModelName, model);
-                bindingContext.ValidationState.Add(model, new ValidationStateEntry() { SuppressValidation = true });
-                bindingContext.Result = ModelBindingResult.Success(bindingContext.ModelName, model);
-            }
 
             return TaskCache.CompletedTask;
         }

src/Microsoft.AspNetCore.Mvc.WebApiCompatShim/HttpRequestMessage/HttpRequestMessageModelBinderProvider.cs

@@ -0,0 +1,25 @@
+// 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.Net.Http;
+using Microsoft.AspNetCore.Mvc.ModelBinding;
+
+namespace Microsoft.AspNetCore.Mvc.WebApiCompatShim
+{
+    /// <summary>
+    /// <see cref="IModelBinderProvider"/> implementation to bind models of type <see cref="HttpRequestMessage"/>.
+    /// </summary>
+    public class HttpRequestMessageModelBinderProvider : IModelBinderProvider
+    {
+        /// <inheritdoc />
+        public IModelBinder GetBinder(ModelBinderProviderContext context)
+        {
+            if (context.Metadata.ModelType == typeof(HttpRequestMessage))
+            {
+                return new HttpRequestMessageModelBinder();
+            }
+
+            return null;
+        }
+    }
+}

src/Microsoft.AspNetCore.Mvc.WebApiCompatShim/WebApiCompatShimOptionsSetup.cs

@@ -28,7 +28,7 @@ namespace Microsoft.AspNetCore.Mvc.WebApiCompatShim
             options.Filters.Add(new HttpResponseExceptionActionFilter());
 
             // Add a model binder to be able to bind HttpRequestMessage
-            options.ModelBinders.Insert(0, new HttpRequestMessageModelBinder());
+            options.ModelBinderProviders.Insert(0, new HttpRequestMessageModelBinderProvider());
 
             // Add a formatter to write out an HttpResponseMessage to the response
             options.OutputFormatters.Insert(0, new HttpResponseMessageOutputFormatter());

test/Microsoft.AspNetCore.Mvc.ApiExplorer.Test/DefaultApiDescriptionProviderTest.cs

@@ -16,6 +16,7 @@ using Microsoft.AspNetCore.Mvc.Filters;
 using Microsoft.AspNetCore.Mvc.Formatters;
 using Microsoft.AspNetCore.Mvc.Internal;
 using Microsoft.AspNetCore.Mvc.ModelBinding;
+using Microsoft.AspNetCore.Mvc.ModelBinding.Binders;
 using Microsoft.AspNetCore.Mvc.Routing;
 using Microsoft.AspNetCore.Routing;
 using Microsoft.AspNetCore.Routing.Constraints;

test/Microsoft.AspNetCore.Mvc.Core.Test/ControllerBaseTest.cs

@@ -1638,7 +1638,6 @@ namespace Microsoft.AspNetCore.Mvc.Core.Test
             var controllerContext = new ControllerContext()
             {
                 HttpContext = httpContext,
-                ModelBinders = new[] { binder, },
                 ValueProviders = new[] { valueProvider, },
                 ValidatorProviders = new[]
                 {
@@ -1649,10 +1648,16 @@ namespace Microsoft.AspNetCore.Mvc.Core.Test
                 },
             };
 
+            var binderFactory = new Mock<IModelBinderFactory>();
+            binderFactory
+                .Setup(f => f.CreateBinder(It.IsAny<ModelBinderFactoryContext>()))
+                .Returns(binder);
+
             var controller = new TestableController()
             {
                 ControllerContext = controllerContext,
                 MetadataProvider = metadataProvider,
+                ModelBinderFactory = binderFactory.Object,
                 ObjectValidator = new DefaultObjectValidator(metadataProvider, new ValidatorCache()),
             };
 

test/Microsoft.AspNetCore.Mvc.Core.Test/Internal/ControllerActionInvokerTest.cs

@@ -2057,7 +2057,6 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                 actionDescriptor,
                 new IInputFormatter[0],
                 actionArgumentsBinder.Object,
-                new IModelBinder[0],
                 new IModelValidatorProvider[0],
                 new IValueProviderFactory[0],
                 new NullLoggerFactory().CreateLogger<ControllerActionInvoker>(),
@@ -2090,9 +2089,6 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                 FilterDescriptors = new List<FilterDescriptor>()
             };
 
-            var binder = new Mock<IModelBinder>();
-            binder.Setup(b => b.BindModelAsync(It.IsAny<DefaultModelBindingContext>()))
-                  .Returns(TaskCache.CompletedTask);
             var context = new Mock<HttpContext>();
             context.SetupGet(c => c.Items)
                    .Returns(new Dictionary<object, object>());
@@ -2115,8 +2111,8 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                 new IInputFormatter[0],
                 new ControllerArgumentBinder(
                     metadataProvider,
+                    TestModelBinderFactory.CreateDefault(metadataProvider),
                     new DefaultObjectValidator(metadataProvider, new ValidatorCache())),
-                new IModelBinder[] { binder.Object },
                 new IModelValidatorProvider[0],
                 new IValueProviderFactory[0],
                 new NullLoggerFactory().CreateLogger<ControllerActionInvoker>(),
@@ -2241,7 +2237,6 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                 ControllerActionDescriptor descriptor,
                 IReadOnlyList<IInputFormatter> inputFormatters,
                 IControllerActionArgumentBinder controllerActionArgumentBinder,
-                IReadOnlyList<IModelBinder> modelBinders,
                 IReadOnlyList<IModelValidatorProvider> modelValidatorProviders,
                 IReadOnlyList<IValueProviderFactory> valueProviderFactories,
                 ILogger logger,
@@ -2254,7 +2249,6 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                       descriptor,
                       inputFormatters,
                       controllerActionArgumentBinder,
-                      modelBinders,
                       modelValidatorProviders,
                       valueProviderFactories,
                       logger,

test/Microsoft.AspNetCore.Mvc.Core.Test/Internal/ControllerArgumentBinderTests.cs

@@ -9,7 +9,6 @@ using Microsoft.AspNetCore.Http.Internal;
 using Microsoft.AspNetCore.Mvc.Abstractions;
 using Microsoft.AspNetCore.Mvc.Controllers;
 using Microsoft.AspNetCore.Mvc.ModelBinding;
-using Microsoft.AspNetCore.Mvc.ModelBinding.Test;
 using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;
 using Microsoft.AspNetCore.Routing;
 using Moq;
@@ -36,17 +35,13 @@ namespace Microsoft.AspNetCore.Mvc.Internal
             binder
                 .Setup(b => b.BindModelAsync(It.IsAny<DefaultModelBindingContext>()))
                 .Returns(TaskCache.CompletedTask);
+            var factory = GetModelBinderFactory(binder.Object);
+            var argumentBinder = GetArgumentBinder(factory);
 
             var controllerContext = GetControllerContext(actionDescriptor);
-            controllerContext.ModelBinders.Add(binder.Object);
-            controllerContext.ValueProviders.Add(new SimpleValueProvider());
-
-            var modelMetadataProvider = TestModelMetadataProvider.CreateDefaultProvider();
-            var argumentBinder = GetArgumentBinder();
 
             // Act
-            var result = await argumentBinder
+            var result = await argumentBinder.BindActionArgumentsAsync(controllerContext, new TestController());
-                .BindActionArgumentsAsync(controllerContext, new TestController());
 
             // Assert
             Assert.Empty(result);
@@ -69,17 +64,13 @@ namespace Microsoft.AspNetCore.Mvc.Internal
             binder
                 .Setup(b => b.BindModelAsync(It.IsAny<DefaultModelBindingContext>()))
                 .Returns(TaskCache.CompletedTask);
+            var factory = GetModelBinderFactory(binder.Object);
+            var argumentBinder = GetArgumentBinder(factory);
 
             var controllerContext = GetControllerContext(actionDescriptor);
-            controllerContext.ModelBinders.Add(binder.Object);
-            controllerContext.ValueProviders.Add(new SimpleValueProvider());
-
-            var argumentBinder = GetArgumentBinder();
-            var modelMetadataProvider = TestModelMetadataProvider.CreateDefaultProvider();
 
             // Act
-            var result = await argumentBinder
+            var result = await argumentBinder.BindActionArgumentsAsync(controllerContext, new TestController());
-                .BindActionArgumentsAsync(controllerContext, new TestController());
 
             // Assert
             Assert.Empty(result);
@@ -111,16 +102,13 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                     context.Result = ModelBindingResult.Success(string.Empty, value);
                 })
                 .Returns(TaskCache.CompletedTask);
+            var factory = GetModelBinderFactory(binder.Object);
+            var argumentBinder = GetArgumentBinder(factory);
 
             var controllerContext = GetControllerContext(actionDescriptor);
-            controllerContext.ModelBinders.Add(binder.Object);
-            controllerContext.ValueProviders.Add(new SimpleValueProvider());
-
-            var argumentBinder = GetArgumentBinder();
 
             // Act
-            var result = await argumentBinder
+            var result = await argumentBinder.BindActionArgumentsAsync(controllerContext, new TestController());
-                .BindActionArgumentsAsync(controllerContext, new TestController());
 
             // Assert
             Assert.Equal(1, result.Count);
@@ -139,7 +127,9 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                     ParameterType = typeof(object),
                 });
 
-            var controllerContext = GetControllerContext(actionDescriptor, "Hello");
+            var controllerContext = GetControllerContext(actionDescriptor);
+
+            var factory = GetModelBinderFactory("Hello");
 
             var mockValidator = new Mock<IObjectModelValidator>(MockBehavior.Strict);
             mockValidator
@@ -150,7 +140,7 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                     It.IsAny<string>(),
                     It.IsAny<object>()));
 
-            var argumentBinder = GetArgumentBinder(mockValidator.Object);
+            var argumentBinder = GetArgumentBinder(factory, mockValidator.Object);
 
             // Act
             var result = await argumentBinder.BindActionArgumentsAsync(controllerContext, new TestController());
@@ -180,15 +170,13 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                     BindingInfo = new BindingInfo(),
                 });
 
+            var controllerContext = GetControllerContext(actionDescriptor);
+
             var binder = new Mock<IModelBinder>();
             binder
                 .Setup(b => b.BindModelAsync(It.IsAny<DefaultModelBindingContext>()))
                 .Returns(TaskCache.CompletedTask);
 
-            var controllerContext = GetControllerContext(actionDescriptor);
-            controllerContext.ModelBinders.Add(binder.Object);
-            controllerContext.ValueProviders.Add(new SimpleValueProvider());
-
             var mockValidator = new Mock<IObjectModelValidator>(MockBehavior.Strict);
             mockValidator
                 .Setup(o => o.Validate(
@@ -198,7 +186,8 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                     It.IsAny<string>(),
                     It.IsAny<object>()));
 
-            var argumentBinder = GetArgumentBinder(mockValidator.Object);
+            var factory = GetModelBinderFactory(binder.Object);
+            var argumentBinder = GetArgumentBinder(factory, mockValidator.Object);
 
             // Act
             var result = await argumentBinder.BindActionArgumentsAsync(controllerContext, new TestController());
@@ -226,7 +215,7 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                     ParameterType = typeof(string),
                 });
 
-            var controllerContext = GetControllerContext(actionDescriptor, "Hello");
+            var controllerContext = GetControllerContext(actionDescriptor);
 
             var mockValidator = new Mock<IObjectModelValidator>(MockBehavior.Strict);
             mockValidator
@@ -237,7 +226,8 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                     It.IsAny<string>(),
                     It.IsAny<object>()));
 
-            var argumentBinder = GetArgumentBinder(mockValidator.Object);
+            var factory = GetModelBinderFactory("Hello");
+            var argumentBinder = GetArgumentBinder(factory, mockValidator.Object);
 
             // Act
             var result = await argumentBinder.BindActionArgumentsAsync(controllerContext, new TestController());
@@ -266,15 +256,13 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                     ParameterType = typeof(string),
                 });
 
+            var controllerContext = GetControllerContext(actionDescriptor);
+
             var binder = new Mock<IModelBinder>();
             binder
                 .Setup(b => b.BindModelAsync(It.IsAny<DefaultModelBindingContext>()))
                 .Returns(TaskCache.CompletedTask);
 
-            var controllerContext = GetControllerContext(actionDescriptor);
-            controllerContext.ModelBinders.Add(binder.Object);
-            controllerContext.ValueProviders.Add(new SimpleValueProvider());
-
             var mockValidator = new Mock<IObjectModelValidator>(MockBehavior.Strict);
             mockValidator
                 .Setup(o => o.Validate(
@@ -284,7 +272,8 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                     It.IsAny<string>(),
                     It.IsAny<object>()));
 
-            var argumentBinder = GetArgumentBinder(mockValidator.Object);
+            var factory = GetModelBinderFactory(binder.Object);
+            var argumentBinder = GetArgumentBinder(factory, mockValidator.Object);
 
             // Act
             var result = await argumentBinder.BindActionArgumentsAsync(controllerContext, new TestController());
@@ -313,8 +302,11 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                     ParameterType = typeof(string)
                 });
 
-            var controllerContext = GetControllerContext(actionDescriptor, "Hello");
+            var controllerContext = GetControllerContext(actionDescriptor);
-            var argumentBinder = GetArgumentBinder();
+
+            var factory = GetModelBinderFactory("Hello");
+            var argumentBinder = GetArgumentBinder(factory);
+
             var controller = new TestController();
 
             // Act
@@ -339,10 +331,12 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                     ParameterType = typeof(ICollection<string>),
                 });
 
-            var expected = new List<string> { "Hello", "World", "!!" };
+            var controllerContext = GetControllerContext(actionDescriptor);
-            var controllerContext = GetControllerContext(actionDescriptor, expected);
+
+            var expected = new List<string> { "Hello", "World", "!!" };
+            var factory = GetModelBinderFactory(expected);
+            var argumentBinder = GetArgumentBinder(factory);
 
-            var argumentBinder = GetArgumentBinder();
             var controller = new TestController();
 
             // Act
@@ -369,13 +363,12 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                     ParameterType = typeof(int)
                 });
 
-            var binder = new StubModelBinder(ModelBindingResult.Success(string.Empty, model: null));
-
             var controllerContext = GetControllerContext(actionDescriptor);
-            controllerContext.ModelBinders.Add(binder);
-            controllerContext.ValueProviders.Add(new SimpleValueProvider());
 
-            var argumentBinder = GetArgumentBinder();
+            var binder = new StubModelBinder(ModelBindingResult.Success(string.Empty, model: null));
+            var factory = GetModelBinderFactory(binder);
+            var argumentBinder = GetArgumentBinder(factory);
+
             var controller = new TestController();
 
             // Some non default value.
@@ -401,13 +394,12 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                     ParameterType = typeof(int?)
                 });
 
-            var binder = new StubModelBinder(ModelBindingResult.Success(key: string.Empty, model: null));
-
             var controllerContext = GetControllerContext(actionDescriptor);
-            controllerContext.ModelBinders.Add(binder);
-            controllerContext.ValueProviders.Add(new SimpleValueProvider());
 
-            var argumentBinder = GetArgumentBinder();
+            var binder = new StubModelBinder(ModelBindingResult.Success(key: string.Empty, model: null));
+            var factory = GetModelBinderFactory(binder);
+            var argumentBinder = GetArgumentBinder(factory);
+
             var controller = new TestController();
 
             // Some non default value.
@@ -478,8 +470,11 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                     ParameterType = propertyType,
                 });
 
-            var controllerContext = GetControllerContext(actionDescriptor, inputValue);
+            var controllerContext = GetControllerContext(actionDescriptor);
-            var argumentBinder = GetArgumentBinder();
+
+            var factory = GetModelBinderFactory(inputValue);
+            var argumentBinder = GetArgumentBinder(factory);
+
             var controller = new TestController();
 
             // Act
@@ -533,8 +528,6 @@ namespace Microsoft.AspNetCore.Mvc.Internal
             }
 
             var controllerContext = GetControllerContext(actionDescriptor);
-            var argumentBinder = GetArgumentBinder();
-            var controller = new TestController();
 
             var binder = new StubModelBinder(bindingContext =>
             {
@@ -550,9 +543,13 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                     bindingContext.Result = ModelBindingResult.Failed(bindingContext.ModelName);
                 }
             });
-            controllerContext.ModelBinders.Add(binder.Object);
+
+            var factory = GetModelBinderFactory(binder);
             controllerContext.ValueProviders.Add(new SimpleValueProvider());
 
+            var argumentBinder = GetArgumentBinder(factory);
+            var controller = new TestController();
+
             // Act
             var result = await argumentBinder.BindActionArgumentsAsync(controllerContext, controller);
 
@@ -574,6 +571,7 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                 RouteData = new RouteData(),
             };
 
+            context.ValueProviders.Add(new SimpleValueProvider());
             return context;
         }
 
@@ -589,37 +587,47 @@ namespace Microsoft.AspNetCore.Mvc.Internal
             };
         }
 
-        private static ControllerContext GetControllerContext(ControllerActionDescriptor descriptor = null, object model = null)
+        private static ModelBinderFactory GetModelBinderFactory(object model = null)
         {
-            var context = new ControllerContext()
-            {
-                ActionDescriptor = descriptor ?? GetActionDescriptor(),
-                HttpContext = new DefaultHttpContext(),
-                RouteData = new RouteData(),
-            };
-
             var binder = new Mock<IModelBinder>();
-            binder.Setup(b => b.BindModelAsync(It.IsAny<DefaultModelBindingContext>()))
+            binder
-                  .Returns<DefaultModelBindingContext>(mbc =>
+                .Setup(b => b.BindModelAsync(It.IsAny<DefaultModelBindingContext>()))
-                  {
+                .Returns<DefaultModelBindingContext>(mbc =>
-                      mbc.Result = ModelBindingResult.Success(string.Empty, model);
+                {
-                      return TaskCache.CompletedTask;
+                    mbc.Result = ModelBindingResult.Success(string.Empty, model);
-                  });
+                    return TaskCache.CompletedTask;
+                });
 
-            context.ModelBinders.Add(binder.Object);
+            return GetModelBinderFactory(binder.Object);
-            context.ValueProviders.Add(new SimpleValueProvider());
-            return context;
         }
 
-        private static ControllerArgumentBinder GetArgumentBinder(IObjectModelValidator validator = null)
+        private static ModelBinderFactory GetModelBinderFactory(IModelBinder binder)
+        {
+            var provider = new Mock<IModelBinderProvider>();
+            provider
+                .Setup(p => p.GetBinder(It.IsAny<ModelBinderProviderContext>()))
+                .Returns(binder);
+
+            return TestModelBinderFactory.Create(provider.Object);
+        }
+
+        private static ControllerArgumentBinder GetArgumentBinder(
+            IModelBinderFactory factory = null,
+            IObjectModelValidator validator = null)
         {
             if (validator == null)
             {
                 validator = CreateMockValidator();
             }
 
+            if (factory == null)
+            {
+                factory = TestModelBinderFactory.CreateDefault();
+            }
+
             return new ControllerArgumentBinder(
                 TestModelMetadataProvider.CreateDefaultProvider(),
+                factory,
                 validator);
         }
 

test/Microsoft.AspNetCore.Mvc.Core.Test/Internal/DefaultBindingMetadataProviderTest.cs

@@ -3,6 +3,7 @@
 
 using Microsoft.AspNetCore.Mvc.Core;
 using Microsoft.AspNetCore.Mvc.ModelBinding;
+using Microsoft.AspNetCore.Mvc.ModelBinding.Binders;
 using Microsoft.AspNetCore.Mvc.ModelBinding.Metadata;
 using Xunit;
 

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/ArrayModelBinderProviderTest.cs

@@ -0,0 +1,92 @@
+// 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;
+using System.Collections.Generic;
+using Moq;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    public class ArrayModelBinderProviderTest
+    {
+        [Theory]
+        [InlineData(typeof(object))]
+        [InlineData(typeof(TestClass))]
+        [InlineData(typeof(IList<int>))]
+        public void Create_ForNonArrayTypes_ReturnsNull(Type modelType)
+        {
+            // Arrange
+            var provider = new ArrayModelBinderProvider();
+            var context = new TestModelBinderProviderContext(modelType);
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.Null(result);
+        }
+
+        [Theory]
+        [InlineData(typeof(byte[]))]
+        [InlineData(typeof(string[]))]
+        [InlineData(typeof(TestClass[]))]
+        [InlineData(typeof(DateTime?[]))]
+        public void Create_ForArrayTypes_ReturnsBinder(Type modelType)
+        {
+            // Arrange
+            var provider = new ArrayModelBinderProvider();
+            var context = new TestModelBinderProviderContext(modelType);
+            context.OnCreatingBinder((m) =>
+            {
+                // Expect to be called with the element type to create a binder for elements.
+                Assert.Equal(modelType.GetElementType(), m.ModelType);
+                return Mock.Of<IModelBinder>();
+            });
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.IsType(typeof(ArrayModelBinder<>).MakeGenericType(modelType.GetElementType()), result);
+        }
+
+        [Fact]
+        public void Create_ForModelMetadataReadOnly_ReturnsNull()
+        {
+            // Arrange
+            var metadataProvider = new TestModelMetadataProvider();
+            metadataProvider.ForProperty(
+                typeof(ModelWithIntArrayProperty),
+                nameof(ModelWithIntArrayProperty.ArrayProperty)).BindingDetails(bd => bd.IsReadOnly = true);
+
+            var modelMetadata = metadataProvider.GetMetadataForProperty(
+                typeof(ModelWithIntArrayProperty),
+                nameof(ModelWithIntArrayProperty.ArrayProperty));
+
+            var provider = new ArrayModelBinderProvider();
+            var context = new TestModelBinderProviderContext(typeof(int[]));
+            context.OnCreatingBinder((m) =>
+            {
+                // Expect to be called with the element type to create a binder for elements.
+                Assert.Equal(typeof(int), m.ModelType);
+                return Mock.Of<IModelBinder>();
+            });
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.IsType<ArrayModelBinder<int>>(result);
+        }
+
+        private class TestClass
+        {
+        }
+
+        private class ModelWithIntArrayProperty
+        {
+            public int[] ArrayProperty { get; set; }
+        }
+    }
+}

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/ArrayModelBinderTest.cs

@@ -4,10 +4,9 @@
 using System.Collections.Generic;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http.Internal;
-using Microsoft.AspNetCore.Mvc.Internal;
 using Xunit;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
     public class ArrayModelBinderTest
     {
@@ -22,7 +21,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
             };
             var bindingContext = GetBindingContext(valueProvider);
             var modelState = bindingContext.ModelState;
-            var binder = new ArrayModelBinder<int>();
+            var binder = new ArrayModelBinder<int>(new SimpleTypeModelBinder());
 
             // Act
             var result = await binder.BindModelResultAsync(bindingContext);
@@ -32,14 +31,13 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
 
             var array = Assert.IsType<int[]>(result.Model);
             Assert.Equal(new[] { 42, 84 }, array);
-            Assert.True(modelState.IsValid);
         }
 
         [Fact]
         public async Task ArrayModelBinder_CreatesEmptyCollection_IfIsTopLevelObject()
         {
             // Arrange
-            var binder = new ArrayModelBinder<string>();
+            var binder = new ArrayModelBinder<string>(new SimpleTypeModelBinder());
 
             var context = CreateContext();
             context.IsTopLevelObject = true;
@@ -69,7 +67,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
         public async Task ArrayModelBinder_DoesNotCreateCollection_IfNotIsTopLevelObject(string prefix)
         {
             // Arrange
-            var binder = new ArrayModelBinder<string>();
+            var binder = new ArrayModelBinder<string>(new SimpleTypeModelBinder());
 
             var context = CreateContext();
             context.ModelName = ModelNames.CreatePropertyModelName(prefix, "ArrayProperty");
@@ -101,28 +99,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
             }
         }
 
-        [Theory]
-        [InlineData(null)]
-        [MemberData(nameof(ArrayModelData))]
-        public async Task BindModelAsync_ModelMetadataReadOnly_ReturnsNull(int[] model)
-        {
-            // Arrange
-            var valueProvider = new SimpleValueProvider
-            {
-                { "someName[0]", "42" },
-                { "someName[1]", "84" },
-            };
-            var bindingContext = GetBindingContext(valueProvider, isReadOnly: true);
-            bindingContext.Model = model;
-            var binder = new ArrayModelBinder<int>();
-
-            // Act
-            var result = await binder.BindModelResultAsync(bindingContext);
-
-            // Assert
-            Assert.Equal(default(ModelBindingResult), result);
-        }
-
         // Here "fails silently" means the call does not update the array but also does not throw or set an error.
         [Theory]
         [MemberData(nameof(ArrayModelData))]
@@ -139,7 +115,8 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
             var bindingContext = GetBindingContext(valueProvider, isReadOnly: false);
             var modelState = bindingContext.ModelState;
             bindingContext.Model = model;
-            var binder = new ArrayModelBinder<int>();
+
+            var binder = new ArrayModelBinder<int>(new SimpleTypeModelBinder());
 
             // Act
             var result = await binder.BindModelResultAsync(bindingContext);
@@ -149,7 +126,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
             Assert.True(result.IsModelSet);
             Assert.Same(model, result.Model);
             
-            Assert.True(modelState.IsValid);
             for (var i = 0; i < arrayLength; i++)
             {
                 // Array should be unchanged.
@@ -191,7 +167,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
                 ValueProvider = valueProvider,
                 OperationBindingContext = new OperationBindingContext
                 {
-                    ModelBinder = CreateIntBinder(),
                     MetadataProvider = metadataProvider,
                 },
             };

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/BinderTypeModelBinderProviderTest.cs

@@ -0,0 +1,58 @@
+// 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;
+using System.Threading.Tasks;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    public class BinderTypeModelBinderProviderTest
+    {
+        [Fact]
+        public void Create_WhenBinderTypeIsNull_ReturnsNull()
+        {
+            // Arrange
+            var provider = new BinderTypeModelBinderProvider();
+
+            var context = new TestModelBinderProviderContext(typeof(Person));
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.Null(result);
+        }
+
+        [Fact]
+        public void Create_WhenBinderTypeIsSet_ReturnsBinder()
+        {
+            // Arrange
+            var provider = new BinderTypeModelBinderProvider();
+
+            var context = new TestModelBinderProviderContext(typeof(Person));
+            context.BindingInfo.BinderType = typeof(NullModelBinder);
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.IsType<BinderTypeModelBinder>(result);
+        }
+
+        private class Person
+        {
+            public string Name { get; set; }
+
+            public int Age { get; set; }
+        }
+
+        private class NullModelBinder : IModelBinder
+        {
+            public Task BindModelAsync(ModelBindingContext bindingContext)
+            {
+                return Task.FromResult(0);
+            }
+        }
+    }
+}

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/BinderTypeModelBinderTest.cs

@@ -5,36 +5,22 @@ using System;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http.Internal;
 using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;
+using Microsoft.AspNetCore.Testing;
 using Microsoft.Extensions.DependencyInjection;
 using Moq;
 using Xunit;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
-    public class BinderTypeBasedModelBinderModelBinderTest
+    public class BinderTypeModelBinderTest
     {
-        [Fact]
-        public async Task BindModel_ReturnsNothing_IfNoBinderTypeIsSet()
-        {
-            // Arrange
-            var bindingContext = GetBindingContext(typeof(Person));
-
-            var binder = new BinderTypeBasedModelBinder();
-
-            // Act
-            var binderResult = await binder.BindModelResultAsync(bindingContext);
-
-            // Assert
-            Assert.Equal(default(ModelBindingResult), binderResult);
-        }
-
         [Fact]
         public async Task BindModel_ReturnsFailedResult_EvenIfSelectedBinderReturnsNull()
         {
             // Arrange
             var bindingContext = GetBindingContext(typeof(Person), binderType: typeof(NullModelBinder));
 
-            var binder = new BinderTypeBasedModelBinder();
+            var binder = new BinderTypeModelBinder(typeof(NullModelBinder));
 
             // Act
             var binderResult = await binder.BindModelResultAsync(bindingContext);
@@ -57,7 +43,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
 
             bindingContext.OperationBindingContext.HttpContext.RequestServices = serviceProvider;
 
-            var binder = new BinderTypeBasedModelBinder();
+            var binder = new BinderTypeModelBinder(typeof(NotNullModelBinder));
 
             // Act
             var binderResult = await binder.BindModelResultAsync(bindingContext);
@@ -69,21 +55,19 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
         }
 
         [Fact]
-        public async Task BindModel_ForNonModelBinder_Throws()
+        public void BindModel_ForNonModelBinder_Throws()
         {
             // Arrange
             var bindingContext = GetBindingContext(typeof(Person), binderType: typeof(Person));
-            var binder = new BinderTypeBasedModelBinder();
 
             var expected = $"The type '{typeof(Person).FullName}' must implement " +
                 $"'{typeof(IModelBinder).FullName}' to be used as a model binder.";
 
-            // Act
+            // Act & Assert
-            var ex = await Assert.ThrowsAsync<InvalidOperationException>(
+            ExceptionAssert.ThrowsArgument(
-                () => binder.BindModelResultAsync(bindingContext));
+                () => new BinderTypeModelBinder(typeof(Person)),
-
+                "binderType",
-            // Assert
+                expected);
-            Assert.Equal(expected, ex.Message);
         }
 
         private static DefaultModelBindingContext GetBindingContext(Type modelType, Type binderType = null)
@@ -108,7 +92,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
                 ValueProvider = Mock.Of<IValueProvider>(),
                 ModelState = new ModelStateDictionary(),
                 OperationBindingContext = operationBindingContext,
-                BinderType = binderType
             };
 
             return bindingContext;

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/BodyModelBinderProviderTest.cs

@@ -0,0 +1,63 @@
+// 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 Xunit;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    public class BodyModelBinderProviderTest
+    {
+        public static TheoryData<BindingSource> NonBodyBindingSources
+        {
+            get
+            {
+                return new TheoryData<BindingSource>()
+                {
+                    BindingSource.Header,
+                    BindingSource.Form,
+                    null,
+                };
+            }
+        }
+
+        [Theory]
+        [MemberData(nameof(NonBodyBindingSources))]
+        public void Create_WhenBindingSourceIsNotFromBody_ReturnsNull(BindingSource source)
+        {
+            // Arrange
+            var provider = new BodyModelBinderProvider(new TestHttpRequestStreamReaderFactory());
+
+            var context = new TestModelBinderProviderContext(typeof(Person));
+            context.BindingInfo.BindingSource = source;
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.Null(result);
+        }
+
+        [Fact]
+        public void Create_WhenBindingSourceIsFromBody_ReturnsBinder()
+        {
+            // Arrange
+            var provider = new BodyModelBinderProvider(new TestHttpRequestStreamReaderFactory());
+
+            var context = new TestModelBinderProviderContext(typeof(Person));
+            context.BindingInfo.BindingSource = BindingSource.Body;
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.IsType<BodyModelBinder>(result);
+        }
+
+        private class Person
+        {
+            public string Name { get; set; }
+
+            public int Age { get; set; }
+        }
+    }
+}

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/BodyModelBinderTests.cs

@@ -14,7 +14,7 @@ using Microsoft.Net.Http.Headers;
 using Moq;
 using Xunit;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
     public class BodyModelBinderTests
     {
@@ -39,7 +39,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 new[] { inputFormatter },
                 metadataProvider: provider);
 
-            var binder = new BodyModelBinder(new TestHttpRequestStreamReaderFactory());
+            var binder = CreateBinder();
 
             // Act
             var binderResult = await binder.BindModelResultAsync(bindingContext);
@@ -60,7 +60,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
 
             var bindingContext = GetBindingContext(typeof(Person), metadataProvider: provider);
 
-            var binder = bindingContext.OperationBindingContext.ModelBinder;
+            var binder = CreateBinder();
 
             // Act
             var binderResult = await binder.BindModelResultAsync(bindingContext);
@@ -88,7 +88,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             var bindingContext = GetBindingContext(typeof(Person), metadataProvider: provider);
             bindingContext.BinderModelName = "custom";
 
-            var binder = bindingContext.OperationBindingContext.ModelBinder;
+            var binder = CreateBinder();
 
             // Act
             var binderResult = await binder.BindModelResultAsync(bindingContext);
@@ -115,7 +115,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
 
             var bindingContext = GetBindingContext(typeof(Person), metadataProvider: provider);
 
-            var binder = bindingContext.OperationBindingContext.ModelBinder;
+            var binder = CreateBinder();
 
             // Act
             var binderResult = await binder.BindModelResultAsync(bindingContext);
@@ -125,44 +125,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             Assert.False(binderResult.IsModelSet);
         }
 
-        [Fact]
-        public async Task BindModel_IsGreedy_IgnoresWrongSource()
-        {
-            // Arrange
-            var provider = new TestModelMetadataProvider();
-            provider.ForType<Person>().BindingDetails(d => d.BindingSource = BindingSource.Header);
-
-            var bindingContext = GetBindingContext(typeof(Person), metadataProvider: provider);
-            bindingContext.BindingSource = BindingSource.Header;
-
-            var binder = bindingContext.OperationBindingContext.ModelBinder;
-
-            // Act
-            var binderResult = await binder.BindModelResultAsync(bindingContext);
-
-            // Assert
-            Assert.Equal(default(ModelBindingResult), binderResult);
-        }
-
-        [Fact]
-        public async Task BindModel_IsGreedy_IgnoresMetadataWithNoSource()
-        {
-            // Arrange
-            var provider = new TestModelMetadataProvider();
-            provider.ForType<Person>().BindingDetails(d => d.BindingSource = null);
-
-            var bindingContext = GetBindingContext(typeof(Person), metadataProvider: provider);
-            bindingContext.BindingSource = null;
-
-            var binder = bindingContext.OperationBindingContext.ModelBinder;
-
-            // Act
-            var binderResult = await binder.BindModelResultAsync(bindingContext);
-
-            // Assert
-            Assert.Equal(default(ModelBindingResult), binderResult);
-        }
-
         [Fact]
         public async Task CustomFormatterDeserializationException_AddedToModelState()
         {
@@ -180,7 +142,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 httpContext: httpContext,
                 metadataProvider: provider);
 
-            var binder = bindingContext.OperationBindingContext.ModelBinder;
+            var binder = CreateBinder();
 
             // Act
             var binderResult = await binder.BindModelResultAsync(bindingContext);
@@ -215,7 +177,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 httpContext: httpContext,
                 metadataProvider: provider);
 
-            var binder = bindingContext.OperationBindingContext.ModelBinder;
+            var binder = CreateBinder();
 
             // Act
             var binderResult = await binder.BindModelResultAsync(bindingContext);
@@ -250,7 +212,8 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             var provider = new TestModelMetadataProvider();
             provider.ForType<Person>().BindingDetails(d => d.BindingSource = BindingSource.Body);
             var bindingContext = GetBindingContext(typeof(Person), inputFormatters, metadataProvider: provider);
-            var binder = bindingContext.OperationBindingContext.ModelBinder;
+
+            var binder = CreateBinder();
 
             // Act
             var binderResult = await binder.BindModelResultAsync(bindingContext);
@@ -288,7 +251,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                     HttpContext = httpContext,
                 },
                 InputFormatters = inputFormatters.ToList(),
-                ModelBinder = new BodyModelBinder(new TestHttpRequestStreamReaderFactory()),
                 MetadataProvider = metadataProvider,
             };
 
@@ -307,6 +269,11 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             return bindingContext;
         }
 
+        private static BodyModelBinder CreateBinder()
+        {
+            return new BodyModelBinder(new TestHttpRequestStreamReaderFactory());
+        }
+
         private class Person
         {
             public string Name { get; set; }

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/ByteArrayModelBinderProviderTest.cs

@@ -0,0 +1,48 @@
+// 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;
+using System.Collections.Generic;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    public class ByteArrayModelBinderProviderTest
+    {
+        [Theory]
+        [InlineData(typeof(object))]
+        [InlineData(typeof(TestClass))]
+        [InlineData(typeof(IList<byte>))]
+        [InlineData(typeof(int[]))]
+        public void Create_ForNonByteArrayTypes_ReturnsNull(Type modelType)
+        {
+            // Arrange
+            var provider = new ByteArrayModelBinderProvider();
+            var context = new TestModelBinderProviderContext(modelType);
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.Null(result);
+        }
+
+        [Fact]
+        public void Create_ForByteArray_ReturnsBinder()
+        {
+            // Arrange
+            var provider = new ByteArrayModelBinderProvider();
+            var context = new TestModelBinderProviderContext(typeof(byte[]));
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.IsType<ByteArrayModelBinder>(result);
+        }
+
+        private class TestClass
+        {
+        }
+    }
+}

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/ByteArrayModelBinderTests.cs

@@ -5,7 +5,7 @@ using System;
 using System.Threading.Tasks;
 using Xunit;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
     public class ByteArrayModelBinderTests
     {
@@ -106,20 +106,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
             Assert.Empty(bindingContext.ModelState); // No submitted data for "foo".
         }
 
-        [Fact]
-        public async Task BindModel_ReturnsNull_ForOtherTypes()
-        {
-            // Arrange
-            var bindingContext = GetBindingContext(new SimpleValueProvider(), typeof(int[]));
-            var binder = new ByteArrayModelBinder();
-
-            // Act
-            var binderResult = await binder.BindModelResultAsync(bindingContext);
-
-            // Assert
-            Assert.Equal(default(ModelBindingResult), binderResult);
-        }
-
         private static DefaultModelBindingContext GetBindingContext(IValueProvider valueProvider, Type modelType)
         {
             var metadataProvider = new EmptyModelMetadataProvider();

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/CancellationTokenModelBinderProviderTest.cs

@@ -0,0 +1,49 @@
+// 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;
+using System.Collections.Generic;
+using System.Threading;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    public class CancellationTokenModelBinderProviderTest
+    {
+        [Theory]
+        [InlineData(typeof(object))]
+        [InlineData(typeof(TestClass))]
+        [InlineData(typeof(IList<int>))]
+        [InlineData(typeof(int[]))]
+        public void Create_ForNonCancellationTokenTypes_ReturnsNull(Type modelType)
+        {
+            // Arrange
+            var provider = new CancellationTokenModelBinderProvider();
+            var context = new TestModelBinderProviderContext(modelType);
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.Null(result);
+        }
+
+        [Fact]
+        public void Create_ForCancellationToken_ReturnsBinder()
+        {
+            // Arrange
+            var provider = new CancellationTokenModelBinderProvider();
+            var context = new TestModelBinderProviderContext(typeof(CancellationToken));
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.IsType<CancellationTokenModelBinder>(result);
+        }
+
+        private class TestClass
+        {
+        }
+    }
+}

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/CancellationTokenModelBinderTests.cs

@@ -8,7 +8,7 @@ using Microsoft.AspNetCore.Http.Internal;
 using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;
 using Xunit;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
     public class CancellationTokenModelBinderTests
     {
@@ -28,23 +28,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
             Assert.Equal(bindingContext.OperationBindingContext.HttpContext.RequestAborted, result.Model);
         }
 
-        [Theory]
-        [InlineData(typeof(int))]
-        [InlineData(typeof(object))]
-        [InlineData(typeof(CancellationTokenModelBinderTests))]
-        public async Task CancellationTokenModelBinder_ReturnsNull_ForNonCancellationTokenType(Type t)
-        {
-            // Arrange
-            var bindingContext = GetBindingContext(t);
-            var binder = new CancellationTokenModelBinder();
-
-            // Act
-            var result = await binder.BindModelResultAsync(bindingContext);
-
-            // Assert
-            Assert.Equal(default(ModelBindingResult), result);
-        }
-
         private static DefaultModelBindingContext GetBindingContext(Type modelType)
         {
             var metadataProvider = new EmptyModelMetadataProvider();
@@ -59,7 +42,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
                     {
                         HttpContext = new DefaultHttpContext(),
                     },
-                    ModelBinder = new CancellationTokenModelBinder(),
                     MetadataProvider = metadataProvider,
                 },
                 ValidationState = new ValidationStateDictionary(),

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/CollectionModelBinderProviderTest.cs

@@ -0,0 +1,111 @@
+// 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;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using Moq;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    public class CollectionModelBinderProviderTest
+    {
+        [Theory]
+        [InlineData(typeof(object))]
+        [InlineData(typeof(int))]
+        [InlineData(typeof(Person))]
+        [InlineData(typeof(int[]))]
+        public void Create_ForNonSupportedTypes_ReturnsNull(Type modelType)
+        {
+            // Arrange
+            var provider = new CollectionModelBinderProvider();
+
+            var context = new TestModelBinderProviderContext(modelType);
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.Null(result);
+        }
+
+        [Theory]
+
+        // These aren't ICollection<> - we can handle them by creating a List<>
+        [InlineData(typeof(IEnumerable<int>))]
+        [InlineData(typeof(IReadOnlyCollection<int>))]
+        [InlineData(typeof(IReadOnlyList<int>))]
+
+        // These are ICollection<> - we can handle them by adding items to the existing collection or
+        // creating a new one.
+        [InlineData(typeof(ICollection<int>))]
+        [InlineData(typeof(IList<int>))]
+        [InlineData(typeof(List<int>))]
+        [InlineData(typeof(Collection<int>))]
+        public void Create_ForSupportedTypes_ReturnsBinder(Type modelType)
+        {
+            // Arrange
+            var provider = new CollectionModelBinderProvider();
+
+            var context = new TestModelBinderProviderContext(modelType);
+
+            Type elementType = null;
+            context.OnCreatingBinder(m =>
+            {
+                Assert.Equal(typeof(int), m.ModelType);
+                elementType = m.ModelType;
+                return Mock.Of<IModelBinder>();
+            });
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.NotNull(elementType);
+            Assert.IsType<CollectionModelBinder<int>>(result);
+        }
+
+        // These aren't ICollection<> - we can handle them by creating a List<> - but in this case
+        // we can't set the property so we can't bind.
+        [Theory]
+        [InlineData(nameof(ReadOnlyProperties.Enumerable))]
+        [InlineData(nameof(ReadOnlyProperties.ReadOnlyCollection))]
+        [InlineData(nameof(ReadOnlyProperties.ReadOnlyList))]
+        public void Create_ForNonICollectionTypes_ReadOnlyProperty_ReturnsNull(string propertyName)
+        {
+            // Arrange
+            var provider = new CollectionModelBinderProvider();
+
+            var metadataProvider = TestModelBinderProviderContext.CachedMetadataProvider;
+
+            var metadata = metadataProvider.GetMetadataForProperty(typeof(ReadOnlyProperties), propertyName);
+            Assert.NotNull(metadata);
+            Assert.True(metadata.IsReadOnly);
+
+            var context = new TestModelBinderProviderContext(metadata, bindingInfo: null);
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.Null(result);
+        }
+
+        private class Person
+        {
+            public string Name { get; set; }
+
+            public int Age { get; set; }
+        }
+
+        private class ReadOnlyProperties
+        {
+            public IEnumerable<int> Enumerable { get; }
+
+            public IReadOnlyCollection<int> ReadOnlyCollection { get; }
+
+            public IReadOnlyList<int> ReadOnlyList { get; }
+        }
+    }
+}

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/CollectionModelBinderTest.cs

@@ -8,11 +8,10 @@ using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http.Internal;
 using Microsoft.AspNetCore.Mvc.Internal;
-using Microsoft.AspNetCore.Mvc.ModelBinding.Test;
 using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;
 using Xunit;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
     public class CollectionModelBinderTest
     {
@@ -26,7 +25,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 { "someName[baz]", "200" }
             };
             var bindingContext = GetModelBindingContext(valueProvider);
-            var binder = new CollectionModelBinder<int>();
+            var binder = new CollectionModelBinder<int>(CreateIntBinder());
 
             // Act
             var collectionResult = await binder.BindComplexCollectionFromIndexes(
@@ -52,7 +51,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 { "someName[3]", "400" }
             };
             var bindingContext = GetModelBindingContext(valueProvider);
-            var binder = new CollectionModelBinder<int>();
+            var binder = new CollectionModelBinder<int>(CreateIntBinder());
 
             // Act
             var boundCollection = await binder.BindComplexCollectionFromIndexes(bindingContext, indexNames: null);
@@ -79,7 +78,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             };
             var bindingContext = GetModelBindingContext(valueProvider, isReadOnly);
             var modelState = bindingContext.ModelState;
-            var binder = new CollectionModelBinder<int>();
+            var binder = new CollectionModelBinder<int>(CreateIntBinder());
 
             // Act
             var result = await binder.BindModelResultAsync(bindingContext);
@@ -111,7 +110,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             var modelState = bindingContext.ModelState;
             var list = new List<int>();
             bindingContext.Model = list;
-            var binder = new CollectionModelBinder<int>();
+            var binder = new CollectionModelBinder<int>(CreateIntBinder());
 
             // Act
             var result = await binder.BindModelResultAsync(bindingContext);
@@ -138,7 +137,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             };
             var bindingContext = GetModelBindingContext(valueProvider, isReadOnly);
             var modelState = bindingContext.ModelState;
-            var binder = new CollectionModelBinder<int>();
+            var binder = new CollectionModelBinder<int>(CreateIntBinder());
 
             // Act
             var result = await binder.BindModelResultAsync(bindingContext);
@@ -165,7 +164,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             var modelState = bindingContext.ModelState;
             var list = new List<int>();
             bindingContext.Model = list;
-            var binder = new CollectionModelBinder<int>();
+            var binder = new CollectionModelBinder<int>(CreateIntBinder());
 
             // Act
             var result = await binder.BindModelResultAsync(bindingContext);
@@ -182,7 +181,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         public async Task BindModelAsync_SimpleCollectionWithNullValue_Succeeds()
         {
             // Arrange
-            var binder = new CollectionModelBinder<int>();
+            var binder = new CollectionModelBinder<int>(CreateIntBinder());
             var valueProvider = new SimpleValueProvider
             {
                 { "someName", null },
@@ -206,7 +205,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         public async Task BindSimpleCollection_RawValueIsEmptyCollection_ReturnsEmptyList()
         {
             // Arrange
-            var binder = new CollectionModelBinder<int>();
+            var binder = new CollectionModelBinder<int>(CreateIntBinder());
             var context = GetModelBindingContext(new SimpleValueProvider());
 
             // Act
@@ -221,7 +220,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         public async Task CollectionModelBinder_CreatesEmptyCollection_IfIsTopLevelObject()
         {
             // Arrange
-            var binder = new CollectionModelBinder<string>();
+            var binder = new CollectionModelBinder<string>(new StubModelBinder(result: null));
 
             var context = CreateContext();
             context.IsTopLevelObject = true;
@@ -251,7 +250,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         public async Task CollectionModelBinder_DoesNotCreateEmptyCollection_IfModelNonNull()
         {
             // Arrange
-            var binder = new CollectionModelBinder<string>();
+            var binder = new CollectionModelBinder<string>(new StubModelBinder(result: null));
 
             var context = CreateContext();
             context.IsTopLevelObject = true;
@@ -285,7 +284,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         public async Task CollectionModelBinder_DoesNotCreateCollection_IfNotIsTopLevelObject(string prefix)
         {
             // Arrange
-            var binder = new CollectionModelBinder<string>();
+            var binder = new CollectionModelBinder<string>(new StubModelBinder(result: null));
 
             var context = CreateContext();
             context.ModelName = ModelNames.CreatePropertyModelName(prefix, "ListProperty");
@@ -326,7 +325,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         public void CanCreateInstance_ReturnsExpectedValue(Type modelType, bool expectedResult)
         {
             // Arrange
-            var binder = new CollectionModelBinder<int>();
+            var binder = new CollectionModelBinder<int>(CreateIntBinder());
 
             // Act
             var result = binder.CanCreateInstance(modelType);
@@ -342,13 +341,13 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             var culture = new CultureInfo("fr-FR");
             var bindingContext = GetModelBindingContext(new SimpleValueProvider());
 
-            bindingContext.OperationBindingContext.ModelBinder = new StubModelBinder(mbc =>
+            var elementBinder = new StubModelBinder(mbc =>
             {
                 Assert.Equal("someName", mbc.ModelName);
                 mbc.Result = ModelBindingResult.Success(mbc.ModelName, 42);
             });
 
-            var modelBinder = new CollectionModelBinder<int>();
+            var modelBinder = new CollectionModelBinder<int>(elementBinder);
 
             // Act
             var boundCollection = await modelBinder.BindSimpleCollection(
@@ -379,7 +378,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 ValueProvider = valueProvider,
                 OperationBindingContext = new OperationBindingContext
                 {
-                    ModelBinder = CreateIntBinder(),
                     MetadataProvider = metadataProvider
                 },
                 ValidationState = new ValidationStateDictionary(),

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/ComplexTypeModelBinderProviderTest.cs

@@ -0,0 +1,65 @@
+// 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;
+using System.Collections.Generic;
+using Moq;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    public class ComplexTypeModelBinderProviderTest
+    {
+        [Theory]
+        [InlineData(typeof(string))]
+        [InlineData(typeof(int))]
+        [InlineData(typeof(List<int>))]
+        public void Create_ForNonComplexType_ReturnsNull(Type modelType)
+        {
+            // Arrange
+            var provider = new ComplexTypeModelBinderProvider();
+
+            var context = new TestModelBinderProviderContext(modelType);
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.Null(result);
+        }
+
+        [Fact]
+        public void Create_ForSupportedTypes_ReturnsBinder()
+        {
+            // Arrange
+            var provider = new ComplexTypeModelBinderProvider();
+
+            var context = new TestModelBinderProviderContext(typeof(Person));
+            context.OnCreatingBinder(m =>
+            {
+                if (m.ModelType == typeof(int) || m.ModelType == typeof(string))
+                {
+                    return Mock.Of<IModelBinder>();
+                }
+                else
+                {
+                    Assert.False(true, "Not the right model type");
+                    return null;
+                }
+            });
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.IsType<ComplexTypeModelBinder>(result);
+        }
+
+        private class Person
+        {
+            public string Name { get; set; }
+
+            public int Age { get; set; }
+        }
+    }
+}

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/ComplexTypeModelBinderTest.cs

@@ -5,20 +5,21 @@ using System;
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.ComponentModel.DataAnnotations;
+using System.Linq;
 using System.Runtime.Serialization;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http.Internal;
 using Microsoft.AspNetCore.Mvc.Internal;
-using Microsoft.AspNetCore.Mvc.ModelBinding.Test;
+using Microsoft.AspNetCore.Mvc.ModelBinding.Internal;
 using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;
 using Microsoft.AspNetCore.Testing;
 using Microsoft.Extensions.DependencyInjection;
 using Moq;
 using Xunit;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
-    public class MutableObjectModelBinderTest
+    public class ComplexTypeModelBinderTest
     {
         private static readonly IModelMetadataProvider _metadataProvider = TestModelMetadataProvider.CreateDefaultProvider();
 
@@ -32,7 +33,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             var bindingContext = CreateContext(GetMetadataForType(typeof(Person)));
             bindingContext.IsTopLevelObject = isTopLevelObject;
 
-            var binder = new TestableMutableObjectModelBinder();
+            var binder = CreateBinder(bindingContext.ModelMetadata);
 
             // Act
             var canCreate = binder.CanCreateModel(bindingContext);
@@ -49,7 +50,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             var bindingContext = CreateContext(modelMetadata);
             bindingContext.IsTopLevelObject = false;
 
-            var binder = new MutableObjectModelBinder();
+            var binder = CreateBinder(bindingContext.ModelMetadata);
 
             // Act
             var canCreate = binder.CanCreateModel(bindingContext);
@@ -64,7 +65,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             var bindingContext = CreateContext(GetMetadataForType(typeof(Document)));
             bindingContext.IsTopLevelObject = true;
 
-            var binder = new MutableObjectModelBinder();
+            var binder = CreateBinder(bindingContext.ModelMetadata);
 
             // Act
             var canCreate = binder.CanCreateModel(bindingContext);
@@ -81,7 +82,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             var bindingContext = CreateContext(GetMetadataForType(typeof(HasAllGreedyProperties)));
             bindingContext.IsTopLevelObject = isTopLevelObject;
 
-            var binder = new TestableMutableObjectModelBinder();
+            var binder = CreateBinder(bindingContext.ModelMetadata);
 
             // Act
             var canCreate = binder.CanCreateModel(bindingContext);
@@ -109,7 +110,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             bindingContext.ValueProvider = valueProvider.Object;
             bindingContext.OperationBindingContext.ValueProvider = valueProvider.Object;
 
-            var binder = new MutableObjectModelBinder();
+            var binder = CreateBinder(bindingContext.ModelMetadata);
 
             // Act
             var canCreate = binder.CanCreateModel(bindingContext);
@@ -126,7 +127,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             var bindingContext = CreateContext(GetMetadataForType(typeof(PersonWithNoProperties)));
             bindingContext.IsTopLevelObject = false;
 
-            var binder = new TestableMutableObjectModelBinder();
+            var binder = CreateBinder(bindingContext.ModelMetadata);
 
             // Act
             var canCreate = binder.CanCreateModel(bindingContext);
@@ -142,7 +143,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             var bindingContext = CreateContext(GetMetadataForType(typeof(PersonWithNoProperties)));
             bindingContext.IsTopLevelObject = true;
 
-            var binder = new TestableMutableObjectModelBinder();
+            var binder = CreateBinder(bindingContext.ModelMetadata);
 
             // Act
             var canCreate = binder.CanCreateModel(bindingContext);
@@ -172,7 +173,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             bindingContext.ValueProvider = valueProvider.Object;
             bindingContext.OperationBindingContext.ValueProvider = valueProvider.Object;
 
-            var binder = new TestableMutableObjectModelBinder();
+            var binder = CreateBinder(bindingContext.ModelMetadata);
 
             // Act
             var canCreate = binder.CanCreateModel(bindingContext);
@@ -207,7 +208,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             bindingContext.ValueProvider = valueProvider.Object;
             bindingContext.OperationBindingContext.ValueProvider = originalValueProvider.Object;
 
-            var binder = new TestableMutableObjectModelBinder();
+            var binder = CreateBinder(bindingContext.ModelMetadata);
 
             // Act
             var canCreate = binder.CanCreateModel(bindingContext);
@@ -240,7 +241,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             bindingContext.ValueProvider = valueProvider.Object;
             bindingContext.OperationBindingContext.ValueProvider = originalValueProvider.Object;
 
-            var binder = new TestableMutableObjectModelBinder();
+            var binder = CreateBinder(bindingContext.ModelMetadata);
 
             // Act
             var canCreate = binder.CanCreateModel(bindingContext);
@@ -269,7 +270,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 ValueProvider = mockValueProvider.Object,
                 OperationBindingContext = new OperationBindingContext
                 {
-                    ModelBinder = mockBinder,
                     MetadataProvider = _metadataProvider,
                     ValidatorProvider = Mock.Of<IModelValidatorProvider>()
                 },
@@ -278,7 +278,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
 
             var model = new Person();
 
-            var testableBinder = new Mock<TestableMutableObjectModelBinder> { CallBase = true };
+            var testableBinder = new Mock<TestableComplexTypeModelBinder> { CallBase = true };
             testableBinder
                 .Setup(o => o.CreateModelPublic(bindingContext))
                 .Returns(model)
@@ -311,7 +311,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             var propertyMetadata = GetMetadataForProperty(typeof(MyModelTestingCanUpdateProperty), propertyName);
 
             // Act
-            var canUpdate = MutableObjectModelBinder.CanUpdatePropertyInternal(propertyMetadata);
+            var canUpdate = ComplexTypeModelBinder.CanUpdatePropertyInternal(propertyMetadata);
 
             // Assert
             Assert.Equal(expected, canUpdate);
@@ -331,7 +331,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             var metadata = metadataProvider.GetMetadataForProperty(typeof(CollectionContainer), propertyName);
 
             // Act
-            var canUpdate = MutableObjectModelBinder.CanUpdatePropertyInternal(metadata);
+            var canUpdate = ComplexTypeModelBinder.CanUpdatePropertyInternal(metadata);
 
             // Assert
             Assert.Equal(expected, canUpdate);
@@ -346,10 +346,10 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 ModelMetadata = GetMetadataForType(typeof(Person))
             };
 
-            var testableBinder = new TestableMutableObjectModelBinder();
+            var binder = CreateBinder(bindingContext.ModelMetadata);
 
             // Act
-            var model = testableBinder.CreateModelPublic(bindingContext);
+            var model = binder.CreateModelPublic(bindingContext);
 
             // Assert
             Assert.IsType<Person>(model);
@@ -362,7 +362,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             var bindingContext = CreateContext(GetMetadataForType(typeof(Person)), new Person());
             var originalModel = bindingContext.Model;
 
-            var binder = new Mock<TestableMutableObjectModelBinder> { CallBase = true };
+            var binder = new Mock<TestableComplexTypeModelBinder>(){ CallBase = true };
             binder
                 .Setup(b => b.CreateModelPublic(It.IsAny<ModelBindingContext>()))
                 .Verifiable();
@@ -381,7 +381,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             // Arrange
             var bindingContext = CreateContext(GetMetadataForType(typeof(Person)), model: null);
 
-            var testableBinder = new Mock<TestableMutableObjectModelBinder> { CallBase = true };
+            var testableBinder = new Mock<TestableComplexTypeModelBinder> { CallBase = true };
             testableBinder
                 .Setup(o => o.CreateModelPublic(bindingContext))
                 .Returns(new Person())
@@ -402,10 +402,8 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         public void CanBindProperty_GetSetProperty(string property)
         {
             // Arrange
-            var binder = new TestableMutableObjectModelBinder();
-
             var metadata = GetMetadataForProperty(typeof(PersonWithBindExclusion), property);
-            var context = new DefaultModelBindingContext()
+            var bindingContext = new DefaultModelBindingContext()
             {
                 ModelMetadata = GetMetadataForType(typeof(PersonWithBindExclusion)),
                 OperationBindingContext = new OperationBindingContext()
@@ -420,8 +418,10 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 },
             };
 
+            var binder = CreateBinder(bindingContext.ModelMetadata);
+
             // Act
-            var result = binder.CanBindPropertyPublic(context, metadata);
+            var result = binder.CanBindPropertyPublic(bindingContext, metadata);
 
             // Assert
             Assert.True(result);
@@ -432,10 +432,8 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         public void CanBindProperty_GetOnlyProperty_WithBindNever(string property)
         {
             // Arrange
-            var binder = new TestableMutableObjectModelBinder();
-
             var metadata = GetMetadataForProperty(typeof(PersonWithBindExclusion), property);
-            var context = new DefaultModelBindingContext()
+            var bindingContext = new DefaultModelBindingContext()
             {
                 ModelMetadata = GetMetadataForType(typeof(PersonWithBindExclusion)),
                 OperationBindingContext = new OperationBindingContext()
@@ -450,8 +448,10 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 },
             };
 
+            var binder = CreateBinder(bindingContext.ModelMetadata);
+
             // Act
-            var result = binder.CanBindPropertyPublic(context, metadata);
+            var result = binder.CanBindPropertyPublic(bindingContext, metadata);
 
             // Assert
             Assert.False(result);
@@ -463,10 +463,8 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         public void CanBindProperty_GetSetProperty_WithBindNever(string property)
         {
             // Arrange
-            var binder = new TestableMutableObjectModelBinder();
-
             var metadata = GetMetadataForProperty(typeof(PersonWithBindExclusion), property);
-            var context = new DefaultModelBindingContext()
+            var bindingContext = new DefaultModelBindingContext()
             {
                 ModelMetadata = GetMetadataForType(typeof(PersonWithBindExclusion)),
                 OperationBindingContext = new OperationBindingContext()
@@ -481,8 +479,10 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 },
             };
 
+            var binder = CreateBinder(bindingContext.ModelMetadata);
+
             // Act
-            var result = binder.CanBindPropertyPublic(context, metadata);
+            var result = binder.CanBindPropertyPublic(bindingContext, metadata);
 
             // Assert
             Assert.False(result);
@@ -496,10 +496,8 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         public void CanBindProperty_WithPredicate(string property, bool expected)
         {
             // Arrange
-            var binder = new TestableMutableObjectModelBinder();
-
             var metadata = GetMetadataForProperty(typeof(TypeWithExcludedPropertiesUsingBindAttribute), property);
-            var context = new DefaultModelBindingContext()
+            var bindingContext = new DefaultModelBindingContext()
             {
                 ModelMetadata = GetMetadataForType(typeof(TypeWithExcludedPropertiesUsingBindAttribute)),
                 OperationBindingContext = new OperationBindingContext()
@@ -514,8 +512,10 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 },
             };
 
+            var binder = CreateBinder(bindingContext.ModelMetadata);
+
             // Act
-            var result = binder.CanBindPropertyPublic(context, metadata);
+            var result = binder.CanBindPropertyPublic(bindingContext, metadata);
 
             // Assert
             Assert.Equal(expected, result);
@@ -529,10 +529,8 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         public void CanBindProperty_WithBindInclude(string property, bool expected)
         {
             // Arrange
-            var binder = new TestableMutableObjectModelBinder();
-
             var metadata = GetMetadataForProperty(typeof(TypeWithIncludedPropertiesUsingBindAttribute), property);
-            var context = new DefaultModelBindingContext()
+            var bindingContext = new DefaultModelBindingContext()
             {
                 ModelMetadata = GetMetadataForType(typeof(TypeWithIncludedPropertiesUsingBindAttribute)),
                 OperationBindingContext = new OperationBindingContext()
@@ -547,8 +545,10 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 },
             };
 
+            var binder = CreateBinder(bindingContext.ModelMetadata);
+
             // Act
-            var result = binder.CanBindPropertyPublic(context, metadata);
+            var result = binder.CanBindPropertyPublic(bindingContext, metadata);
 
             // Assert
             Assert.Equal(expected, result);
@@ -561,10 +561,8 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         public void CanBindProperty_BindingAttributes_OverridingBehavior(string property, bool expected)
         {
             // Arrange
-            var binder = new TestableMutableObjectModelBinder();
-
             var metadata = GetMetadataForProperty(typeof(ModelWithMixedBindingBehaviors), property);
-            var context = new DefaultModelBindingContext()
+            var bindingContext = new DefaultModelBindingContext()
             {
                 ModelMetadata = GetMetadataForType(typeof(ModelWithMixedBindingBehaviors)),
                 OperationBindingContext = new OperationBindingContext()
@@ -579,8 +577,10 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 },
             };
 
+            var binder = CreateBinder(bindingContext.ModelMetadata);
+
             // Act
-            var result = binder.CanBindPropertyPublic(context, metadata);
+            var result = binder.CanBindPropertyPublic(bindingContext, metadata);
 
             // Assert
             Assert.Equal(expected, result);
@@ -597,13 +597,13 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 Age = -20
             };
 
-            var binder = new TestableMutableObjectModelBinder();
-
             var property = GetMetadataForProperty(model.GetType(), nameof(ModelWithBindRequired.Age));
-            binder.Results[property] = ModelBindingResult.Failed("theModel.Age");
 
             var bindingContext = CreateContext(GetMetadataForType(model.GetType()), model);
 
+            var binder = CreateBinder(bindingContext.ModelMetadata);
+            binder.Results[property] = ModelBindingResult.Failed("theModel.Age");
+
             // Act
             await binder.BindModelAsync(bindingContext);
 
@@ -632,13 +632,13 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 Age = -20
             };
 
-            var binder = new TestableMutableObjectModelBinder();
+            var bindingContext = CreateContext(GetMetadataForType(model.GetType()), model);
+
+            var binder = CreateBinder(bindingContext.ModelMetadata);
 
             var property = GetMetadataForProperty(model.GetType(), nameof(ModelWithDataMemberIsRequired.Age));
             binder.Results[property] = ModelBindingResult.Failed("theModel.Age");
 
-            var bindingContext = CreateContext(GetMetadataForType(model.GetType()), model);
-
             // Act
             await binder.BindModelAsync(bindingContext);
 
@@ -667,15 +667,15 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 Age = -20
             };
 
-            var binder = new TestableMutableObjectModelBinder();
+            var bindingContext = CreateContext(GetMetadataForType(model.GetType()), model);
+
+            var binder = CreateBinder(bindingContext.ModelMetadata);
 
             // Attempt to set non-Nullable property to null. BindRequiredAttribute should not be relevant in this
             // case because the property did have a result.
             var property = GetMetadataForProperty(model.GetType(), nameof(ModelWithBindRequired.Age));
             binder.Results[property] = ModelBindingResult.Success("theModel.Age", model: null);
 
-            var bindingContext = CreateContext(GetMetadataForType(model.GetType()), model);
-
             // Act
             await binder.BindModelAsync(bindingContext);
 
@@ -701,7 +701,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             var model = new BindingOptionalProperty();
             var bindingContext = CreateContext(GetMetadataForType(model.GetType()), model);
 
-            var binder = new TestableMutableObjectModelBinder();
+            var binder = CreateBinder(bindingContext.ModelMetadata);
 
             var property = GetMetadataForProperty(model.GetType(), nameof(BindingOptionalProperty.ValueTypeRequired));
             binder.Results[property] = ModelBindingResult.Failed("theModel.ValueTypeRequired");
@@ -721,7 +721,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             var model = new NullableValueTypeProperty();
             var bindingContext = CreateContext(GetMetadataForType(model.GetType()), model);
 
-            var binder = new TestableMutableObjectModelBinder();
+            var binder = CreateBinder(bindingContext.ModelMetadata);
 
             var property = GetMetadataForProperty(model.GetType(), nameof(NullableValueTypeProperty.NullableValueType));
             binder.Results[property] = ModelBindingResult.Failed("theModel.NullableValueType");
@@ -743,7 +743,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
 
             var bindingContext = CreateContext(containerMetadata, model);
 
-            var binder = new TestableMutableObjectModelBinder();
+            var binder = CreateBinder(bindingContext.ModelMetadata);
 
             var property = GetMetadataForProperty(model.GetType(), nameof(Person.ValueTypeRequired));
             binder.Results[property] = ModelBindingResult.Failed("theModel." + nameof(Person.ValueTypeRequired));
@@ -765,7 +765,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
 
             var bindingContext = CreateContext(containerMetadata, model);
 
-            var binder = new TestableMutableObjectModelBinder();
+            var binder = CreateBinder(bindingContext.ModelMetadata);
 
             var property = GetMetadataForProperty(model.GetType(), nameof(Person.ValueTypeRequired));
             binder.Results[property] = ModelBindingResult.Success(
@@ -794,7 +794,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
 
             var bindingContext = CreateContext(containerMetadata, model);
 
-            var binder = new TestableMutableObjectModelBinder();
+            var binder = CreateBinder(bindingContext.ModelMetadata);
 
             foreach (var property in containerMetadata.Properties)
             {
@@ -833,10 +833,10 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             var propertyMetadata = metadata.Properties[nameof(model.PropertyWithDefaultValue)];
 
             var result = ModelBindingResult.Failed("foo");
-            var testableBinder = new TestableMutableObjectModelBinder();
+            var binder = CreateBinder(bindingContext.ModelMetadata);
 
             // Act
-            testableBinder.SetPropertyPublic(bindingContext, propertyMetadata, result);
+            binder.SetPropertyPublic(bindingContext, propertyMetadata, result);
 
             // Assert
             var person = Assert.IsType<Person>(bindingContext.Model);
@@ -858,10 +858,10 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             // The null model value won't be used because IsModelBound = false.
             var result = ModelBindingResult.Failed("foo");
 
-            var testableBinder = new TestableMutableObjectModelBinder();
+            var binder = CreateBinder(bindingContext.ModelMetadata);
 
             // Act
-            testableBinder.SetPropertyPublic(bindingContext, propertyMetadata, result);
+            binder.SetPropertyPublic(bindingContext, propertyMetadata, result);
 
             // Assert
             var person = Assert.IsType<Person>(bindingContext.Model);
@@ -883,10 +883,10 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             // The null model value won't be used because IsModelBound = false.
             var result = ModelBindingResult.Failed("foo");
 
-            var testableBinder = new TestableMutableObjectModelBinder();
+            var binder = CreateBinder(bindingContext.ModelMetadata);
 
             // Act
-            testableBinder.SetPropertyPublic(bindingContext, propertyMetadata, result);
+            binder.SetPropertyPublic(bindingContext, propertyMetadata, result);
 
             // Assert
             var person = Assert.IsType<Person>(bindingContext.Model);
@@ -906,10 +906,10 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             var propertyMetadata = metadata.Properties[nameof(model.NonUpdateableProperty)];
 
             var result = ModelBindingResult.Failed("foo");
-            var testableBinder = new TestableMutableObjectModelBinder();
+            var binder = CreateBinder(bindingContext.ModelMetadata);
 
             // Act
-            testableBinder.SetPropertyPublic(bindingContext, propertyMetadata, result);
+            binder.SetPropertyPublic(bindingContext, propertyMetadata, result);
 
             // Assert
             // If didn't throw, success!
@@ -953,10 +953,10 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 propertyName,
                 new Simple { Name = "Hanna" });
 
-            var testableBinder = new TestableMutableObjectModelBinder();
+            var binder = CreateBinder(bindingContext.ModelMetadata);
 
             // Act
-            testableBinder.SetPropertyPublic(bindingContext, propertyMetadata, result);
+            binder.SetPropertyPublic(bindingContext, propertyMetadata, result);
 
             // Assert
             Assert.Equal("Joe", propertyAccessor(model));
@@ -977,7 +977,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             var bindingContext = CreateContext(modelMetadata, model);
             var result = ModelBindingResult.Success(propertyMetadata.PropertyName, new List<string>() { "hi" });
 
-            var binder = new TestableMutableObjectModelBinder();
+            var binder = CreateBinder(bindingContext.ModelMetadata);
 
             // Act
             binder.SetPropertyPublic(bindingContext, propertyMetadata, result);
@@ -999,10 +999,10 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             var propertyMetadata = bindingContext.ModelMetadata.Properties[nameof(model.DateOfBirth)];
 
             var result = ModelBindingResult.Success("foo", new DateTime(2001, 1, 1));
-            var testableBinder = new TestableMutableObjectModelBinder();
+            var binder = CreateBinder(bindingContext.ModelMetadata);
 
             // Act
-            testableBinder.SetPropertyPublic(bindingContext, propertyMetadata, result);
+            binder.SetPropertyPublic(bindingContext, propertyMetadata, result);
 
             // Assert
             Assert.True(bindingContext.ModelState.IsValid);
@@ -1026,10 +1026,10 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             var propertyMetadata = bindingContext.ModelMetadata.Properties[nameof(model.DateOfDeath)];
 
             var result = ModelBindingResult.Success("foo", new DateTime(1800, 1, 1));
-            var testableBinder = new TestableMutableObjectModelBinder();
+            var binder = CreateBinder(bindingContext.ModelMetadata);
 
             // Act
-            testableBinder.SetPropertyPublic(bindingContext, propertyMetadata, result);
+            binder.SetPropertyPublic(bindingContext, propertyMetadata, result);
 
             // Assert
             Assert.Equal("Date of death can't be before date of birth." + Environment.NewLine
@@ -1051,10 +1051,10 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             var propertyMetadata = bindingContext.ModelMetadata.Properties[nameof(model.NameNoAttribute)];
 
             var result = ModelBindingResult.Success("foo.NameNoAttribute", model: null);
-            var testableBinder = new TestableMutableObjectModelBinder();
+            var binder = CreateBinder(bindingContext.ModelMetadata);
 
             // Act
-            testableBinder.SetPropertyPublic(bindingContext, propertyMetadata, result);
+            binder.SetPropertyPublic(bindingContext, propertyMetadata, result);
 
             // Assert
             Assert.False(bindingContext.ModelState.IsValid);
@@ -1064,6 +1064,30 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                          bindingContext.ModelState["foo.NameNoAttribute"].Errors[0].Exception.Message);
         }
 
+        private static TestableComplexTypeModelBinder CreateBinder(ModelMetadata metadata)
+        {
+            var options = new TestOptionsManager<MvcOptions>();
+            MvcCoreMvcOptionsSetup.ConfigureMvc(options.Value, new TestHttpRequestStreamReaderFactory());
+
+            var lastIndex = options.Value.ModelBinderProviders.Count - 1;
+            Assert.IsType<ComplexTypeModelBinderProvider>(options.Value.ModelBinderProviders[lastIndex]);
+            options.Value.ModelBinderProviders.RemoveAt(lastIndex);
+            options.Value.ModelBinderProviders.Add(new TestableComplexTypeModelBinderProvider());
+
+            var factory = TestModelBinderFactory.Create(options.Value.ModelBinderProviders.ToArray());
+            return (TestableComplexTypeModelBinder)factory.CreateBinder(new ModelBinderFactoryContext()
+            {
+                Metadata = metadata,
+                BindingInfo = new BindingInfo()
+                {
+                    BinderModelName = metadata.BinderModelName,
+                    BinderType = metadata.BinderType,
+                    BindingSource = metadata.BindingSource,
+                    PropertyBindingPredicateProvider = metadata.PropertyBindingPredicateProvider,
+                },
+            });
+        }
+
         private static DefaultModelBindingContext CreateContext(ModelMetadata metadata, object model = null)
         {
             var valueProvider = new TestValueProvider(new Dictionary<string, object>());
@@ -1281,7 +1305,10 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
 
         private class NonValueBinderMetadataAttribute : Attribute, IBindingSourceMetadata
         {
-            public BindingSource BindingSource { get { return BindingSource.Body; } }
+            public BindingSource BindingSource
+            {
+                get { return new BindingSource("Special", string.Empty, isGreedy: true, isFromRequest: true); }
+            }
         }
 
         private class ValueBinderMetadataAttribute : Attribute, IBindingSourceMetadata
@@ -1333,10 +1360,35 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             public IList<int> SettableList { get; set; } = new List<int> { 3, 9, 0 };
         }
 
-        // Provides the ability to easily mock + call each of these APIs
+        private class TestableComplexTypeModelBinderProvider : IModelBinderProvider
-        public class TestableMutableObjectModelBinder : MutableObjectModelBinder
         {
-            public TestableMutableObjectModelBinder()
+            public IModelBinder GetBinder(ModelBinderProviderContext context)
+            {
+                if (context.Metadata.IsComplexType)
+                {
+                    var propertyBinders = new Dictionary<ModelMetadata, IModelBinder>();
+                    foreach (var property in context.Metadata.Properties)
+                    {
+                        propertyBinders.Add(property, context.CreateBinder(property));
+                    }
+
+                    return new TestableComplexTypeModelBinder(propertyBinders);
+                }
+
+                return null;
+            }
+        }
+
+        // Provides the ability to easily mock + call each of these APIs
+        public class TestableComplexTypeModelBinder : ComplexTypeModelBinder
+        {
+            public TestableComplexTypeModelBinder()
+                : this(new Dictionary<ModelMetadata, IModelBinder>())
+            {
+            }
+
+            public TestableComplexTypeModelBinder(IDictionary<ModelMetadata, IModelBinder> propertyBinders)
+                : base(propertyBinders)
             {
                 Results = new Dictionary<ModelMetadata, ModelBindingResult>();
             }

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/DictionaryModelBinderProviderTest.cs

@@ -0,0 +1,70 @@
+// 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;
+using System.Collections.Generic;
+using Moq;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    public class DictionaryModelBinderProviderTest
+    {
+        [Theory]
+        [InlineData(typeof(Person))]
+        [InlineData(typeof(string))]
+        [InlineData(typeof(IEnumerable<KeyValuePair<string, int>>))]
+        [InlineData(typeof(ICollection<string>))]
+        public void Create_ForNonDictionaryType_ReturnsNull(Type modelType)
+        {
+            // Arrange
+            var provider = new DictionaryModelBinderProvider();
+
+            var context = new TestModelBinderProviderContext(modelType);
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.Null(result);
+        }
+
+        [Theory]
+        [InlineData(typeof(IDictionary<string, int>))]
+        [InlineData(typeof(Dictionary<string, int>))]
+        public void Create_ForDictionaryType_ReturnsBinder(Type modelType)
+        {
+            // Arrange
+            var provider = new DictionaryModelBinderProvider();
+
+            var context = new TestModelBinderProviderContext(modelType);
+            context.OnCreatingBinder(m =>
+            {
+                if (m.ModelType == typeof(KeyValuePair<string, int>) ||
+                    m.ModelType == typeof(int) ||
+                    m.ModelType == typeof(string))
+                {
+                    return Mock.Of<IModelBinder>();
+                }
+                else
+                {
+                    Assert.False(true, "Not the right model type");
+                    return null;
+                }
+            });
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.IsType<DictionaryModelBinder<string, int>>(result);
+        }
+
+        private class Person
+        {
+            public string Name { get; set; }
+
+            public int Age { get; set; }
+        }
+    }
+}

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/DictionaryModelBinderTest.cs

@@ -10,10 +10,9 @@ using Microsoft.AspNetCore.Http.Internal;
 using Microsoft.AspNetCore.Mvc.Internal;
 using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;
 using Microsoft.Extensions.Primitives;
-using Moq;
 using Xunit;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
     public class DictionaryModelBinderTest
     {
@@ -23,25 +22,28 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
         public async Task BindModel_Succeeds(bool isReadOnly)
         {
             // Arrange
-            var values = new Dictionary<string, KeyValuePair<int, string>>()
+            var values = new Dictionary<string, string>()
             {
-                { "someName[0]", new KeyValuePair<int, string>(42, "forty-two") },
+                { "someName[0].Key", "42" },
-                { "someName[1]", new KeyValuePair<int, string>(84, "eighty-four") },
+                { "someName[0].Value", "forty-two" },
+                { "someName[1].Key", "84" },
+                { "someName[1].Value", "eighty-four" },
             };
 
+            // Value Provider
+
             var bindingContext = GetModelBindingContext(isReadOnly, values);
-            var modelState = bindingContext.ModelState;
+            bindingContext.ValueProvider = CreateEnumerableValueProvider("{0}", values);
-            var binder = new DictionaryModelBinder<int, string>();
+
+            var binder = new DictionaryModelBinder<int, string>(new SimpleTypeModelBinder(), new SimpleTypeModelBinder());
 
             // Act
             var result = await binder.BindModelResultAsync(bindingContext);
 
             // Assert
-            Assert.NotEqual(default(ModelBindingResult), result);
             Assert.True(result.IsModelSet);
-            var dictionary = Assert.IsAssignableFrom<IDictionary<int, string>>(result.Model);
-            Assert.True(modelState.IsValid);
 
+            var dictionary = Assert.IsAssignableFrom<IDictionary<int, string>>(result.Model);
             Assert.NotNull(dictionary);
             Assert.Equal(2, dictionary.Count);
             Assert.Equal("forty-two", dictionary[42]);
@@ -57,27 +59,29 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
         public async Task BindModel_WithExistingModel_Succeeds(bool isReadOnly)
         {
             // Arrange
-            var values = new Dictionary<string, KeyValuePair<int, string>>()
+            var values = new Dictionary<string, string>()
             {
-                { "someName[0]", new KeyValuePair<int, string>(42, "forty-two") },
+                { "someName[0].Key", "42" },
-                { "someName[1]", new KeyValuePair<int, string>(84, "eighty-four") },
+                { "someName[0].Value", "forty-two" },
+                { "someName[1].Key", "84" },
+                { "someName[1].Value", "eighty-four" },
             };
 
             var bindingContext = GetModelBindingContext(isReadOnly, values);
-            var modelState = bindingContext.ModelState;
+            bindingContext.ValueProvider = CreateEnumerableValueProvider("{0}", values);
+
             var dictionary = new Dictionary<int, string>();
             bindingContext.Model = dictionary;
-            var binder = new DictionaryModelBinder<int, string>();
+
+            var binder = new DictionaryModelBinder<int, string>(new SimpleTypeModelBinder(), new SimpleTypeModelBinder());
 
             // Act
             var result = await binder.BindModelResultAsync(bindingContext);
 
             // Assert
-            Assert.NotEqual(default(ModelBindingResult), result);
             Assert.True(result.IsModelSet);
-            Assert.Same(dictionary, result.Model);
-            Assert.True(modelState.IsValid);
 
+            Assert.Same(dictionary, result.Model);
             Assert.NotNull(dictionary);
             Assert.Equal(2, dictionary.Count);
             Assert.Equal("forty-two", dictionary[42]);
@@ -123,10 +127,10 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
             IDictionary<string, string> dictionary)
         {
             // Arrange
-            var binder = new DictionaryModelBinder<string, string>();
+            var binder = new DictionaryModelBinder<string, string>(new SimpleTypeModelBinder(), new SimpleTypeModelBinder());
+
             var context = CreateContext();
             context.ModelName = modelName;
-            context.OperationBindingContext.ModelBinder = CreateCompositeBinder();
             context.OperationBindingContext.ValueProvider = CreateEnumerableValueProvider(keyFormat, dictionary);
             context.ValueProvider = context.OperationBindingContext.ValueProvider;
             context.FieldName = modelName;
@@ -140,7 +144,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
             var result = await binder.BindModelResultAsync(context);
 
             // Assert
-            Assert.NotEqual(default(ModelBindingResult), result);
             Assert.True(result.IsModelSet);
             Assert.Equal(modelName, result.Key);
 
@@ -160,10 +163,10 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
                 { "three", "three" },
             };
 
-            var binder = new DictionaryModelBinder<string, string>();
+            var binder = new DictionaryModelBinder<string, string>(new SimpleTypeModelBinder(), new SimpleTypeModelBinder());
+
             var context = CreateContext();
             context.ModelName = "prefix";
-            context.OperationBindingContext.ModelBinder = CreateCompositeBinder();
             context.OperationBindingContext.ValueProvider = CreateTestValueProvider("prefix[{0}]", dictionary);
             context.ValueProvider = context.OperationBindingContext.ValueProvider;
             context.FieldName = context.ModelName;
@@ -210,10 +213,11 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
         {
             // Arrange
             var stringDictionary = dictionary.ToDictionary(kvp => kvp.Key.ToString(), kvp => kvp.Value.ToString());
-            var binder = new DictionaryModelBinder<long, int>();
+
+            var binder = new DictionaryModelBinder<long, int>(new SimpleTypeModelBinder(), new SimpleTypeModelBinder());
+
             var context = CreateContext();
             context.ModelName = "prefix";
-            context.OperationBindingContext.ModelBinder = CreateCompositeBinder();
             context.OperationBindingContext.ValueProvider =
                 CreateEnumerableValueProvider("prefix[{0}]", stringDictionary);
             context.ValueProvider = context.OperationBindingContext.ValueProvider;
@@ -252,10 +256,9 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
                 { "prefix[27].Id", "98" },
                 { "prefix[27].Name", "Fred" },
             };
-            var binder = new DictionaryModelBinder<int, ModelWithProperties>();
+
             var context = CreateContext();
             context.ModelName = "prefix";
-            context.OperationBindingContext.ModelBinder = CreateCompositeBinder();
             context.OperationBindingContext.ValueProvider = CreateEnumerableValueProvider("{0}", stringDictionary);
             context.ValueProvider = context.OperationBindingContext.ValueProvider;
             context.FieldName = context.ModelName;
@@ -265,6 +268,16 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
                 typeof(ModelWithDictionaryProperties),
                 nameof(ModelWithDictionaryProperties.DictionaryWithComplexValuesProperty));
 
+            var valueMetadata = metadataProvider.GetMetadataForType(typeof(ModelWithProperties));
+
+            var binder = new DictionaryModelBinder<int, ModelWithProperties>(
+                new SimpleTypeModelBinder(),
+                new ComplexTypeModelBinder(new Dictionary<ModelMetadata, IModelBinder>()
+                {
+                    { valueMetadata.Properties["Id"], new SimpleTypeModelBinder() },
+                    { valueMetadata.Properties["Name"], new SimpleTypeModelBinder() },
+                }));
+
             // Act
             var result = await binder.BindModelResultAsync(context);
 
@@ -298,10 +311,11 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
         {
             // Arrange
             var expectedDictionary = new SortedDictionary<string, string>(dictionary);
-            var binder = new DictionaryModelBinder<string, string>();
+            var binder = new DictionaryModelBinder<string, string>(new SimpleTypeModelBinder(), new SimpleTypeModelBinder());
+
             var context = CreateContext();
             context.ModelName = modelName;
-            context.OperationBindingContext.ModelBinder = CreateCompositeBinder();
+
             context.OperationBindingContext.ValueProvider = CreateEnumerableValueProvider(keyFormat, dictionary);
             context.ValueProvider = context.OperationBindingContext.ValueProvider;
             context.FieldName = context.ModelName;
@@ -327,7 +341,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
         public async Task DictionaryModelBinder_CreatesEmptyCollection_IfIsTopLevelObject()
         {
             // Arrange
-            var binder = new DictionaryModelBinder<string, string>();
+            var binder = new DictionaryModelBinder<string, string>(new SimpleTypeModelBinder(), new SimpleTypeModelBinder());
 
             var context = CreateContext();
             context.IsTopLevelObject = true;
@@ -357,7 +371,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
         public async Task DictionaryModelBinder_DoesNotCreateCollection_IfNotIsTopLevelObject(string prefix)
         {
             // Arrange
-            var binder = new DictionaryModelBinder<string, string>();
+            var binder = new DictionaryModelBinder<int, int>(new SimpleTypeModelBinder(), new SimpleTypeModelBinder());
 
             var context = CreateContext();
             context.ModelName = ModelNames.CreatePropertyModelName(prefix, "ListProperty");
@@ -399,7 +413,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
         public void CanCreateInstance_ReturnsExpectedValue(Type modelType, bool expectedResult)
         {
             // Arrange
-            var binder = new DictionaryModelBinder<int, int>();
+            var binder = new DictionaryModelBinder<int, int>(new SimpleTypeModelBinder(), new SimpleTypeModelBinder());
 
             // Act
             var result = binder.CanCreateInstance(modelType);
@@ -427,17 +441,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
             return modelBindingContext;
         }
 
-        private static IModelBinder CreateCompositeBinder()
-        {
-            var binders = new IModelBinder[]
-            {
-                new SimpleTypeModelBinder(),
-                new MutableObjectModelBinder(),
-            };
-
-            return new CompositeModelBinder(binders);
-        }
-
         private static IValueProvider CreateEnumerableValueProvider(
             string keyFormat,
             IDictionary<string, string> dictionary)
@@ -468,7 +471,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
 
         private static DefaultModelBindingContext GetModelBindingContext(
             bool isReadOnly,
-            IDictionary<string, KeyValuePair<int, string>> values)
+            IDictionary<string, string> values = null)
         {
             var metadataProvider = new TestModelMetadataProvider();
             metadataProvider
@@ -478,15 +481,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
                 typeof(ModelWithIDictionaryProperty),
                 nameof(ModelWithIDictionaryProperty.DictionaryProperty));
 
-            var binder = new StubModelBinder(mbc =>
-            {
-                KeyValuePair<int, string> value;
-                if (values.TryGetValue(mbc.ModelName, out value))
-                {
-                    mbc.Result = ModelBindingResult.Success(mbc.ModelName, value);
-                }
-            });
-
             var valueProvider = new SimpleValueProvider();
             foreach (var kvp in values)
             {
@@ -500,7 +494,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
                 ModelState = new ModelStateDictionary(),
                 OperationBindingContext = new OperationBindingContext
                 {
-                    ModelBinder = binder.Object,
                     MetadataProvider = metadataProvider,
                     ValueProvider = valueProvider,
                 },

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/FormCollectionModelBinderProviderTest.cs

@@ -0,0 +1,50 @@
+// 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;
+using System.Collections.Generic;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Http.Internal;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    public class FormCollectionModelBinderProviderTest
+    {
+        [Theory]
+        [InlineData(typeof(FormCollection))]
+        [InlineData(typeof(TestClass))]
+        [InlineData(typeof(IList<int>))]
+        [InlineData(typeof(int[]))]
+        public void Create_ForNonFormCollectionTypes_ReturnsNull(Type modelType)
+        {
+            // Arrange
+            var provider = new FormCollectionModelBinderProvider();
+            var context = new TestModelBinderProviderContext(modelType);
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.Null(result);
+        }
+
+        [Fact]
+        public void Create_ForFormCollectionToken_ReturnsBinder()
+        {
+            // Arrange
+            var provider = new FormCollectionModelBinderProvider();
+            var context = new TestModelBinderProviderContext(typeof(IFormCollection));
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.IsType<FormCollectionModelBinder>(result);
+        }
+
+        private class TestClass
+        {
+        }
+    }
+}

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/FormCollectionModelBinderTest.cs

@@ -12,7 +12,7 @@ using Microsoft.Extensions.Primitives;
 using Moq;
 using Xunit;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
     public class FormCollectionModelBinderTest
     {
@@ -47,47 +47,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             Assert.Equal("value2", form["field2"]);
         }
 
-        [Fact]
-        public async Task FormCollectionModelBinder_InvalidType_BindFails()
-        {
-            // Arrange
-            var formCollection = new FormCollection(new Dictionary<string, StringValues>
-            {
-                { "field1", "value1" },
-                { "field2", "value2" }
-            });
-            var httpContext = GetMockHttpContext(formCollection);
-            var bindingContext = GetBindingContext(typeof(string), httpContext);
-            var binder = new FormCollectionModelBinder();
-
-            // Act
-            var result = await binder.BindModelResultAsync(bindingContext);
-
-            // Assert
-            Assert.Equal(default(ModelBindingResult), result);
-        }
-
-        // We only support IFormCollection here. Using the concrete type won't work.
-        [Fact]
-        public async Task FormCollectionModelBinder_FormCollectionConcreteType_BindFails()
-        {
-            // Arrange
-            var formCollection = new FormCollection(new Dictionary<string, StringValues>
-            {
-                { "field1", "value1" },
-                { "field2", new string[] { "value2" } }
-            });
-            var httpContext = GetMockHttpContext(formCollection);
-            var bindingContext = GetBindingContext(typeof(FormCollection), httpContext);
-            var binder = new FormCollectionModelBinder();
-
-            // Act
-            var result = await binder.BindModelResultAsync(bindingContext);
-
-            // Assert
-            Assert.Equal(default(ModelBindingResult), result);
-        }
-
         [Fact]
         public async Task FormCollectionModelBinder_NoForm_BindSuccessful_ReturnsEmptyFormCollection()
         {
@@ -127,7 +86,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                     {
                         HttpContext = httpContext,
                     },
-                    ModelBinder = new FormCollectionModelBinder(),
                     MetadataProvider = metadataProvider,
                 },
                 ValidationState = new ValidationStateDictionary(),

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/FormFileModelBinderProviderTest.cs

@@ -0,0 +1,55 @@
+// 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;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using Microsoft.AspNetCore.Http;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    public class FormFileModelBinderProviderTest
+    {
+        [Theory]
+        [InlineData(typeof(object))]
+        [InlineData(typeof(IFormCollection))]
+        [InlineData(typeof(TestClass))]
+        [InlineData(typeof(IList<int>))]
+        public void Create_ForUnsupportedTypes_ReturnsNull(Type modelType)
+        {
+            // Arrange
+            var provider = new FormFileModelBinderProvider();
+            var context = new TestModelBinderProviderContext(modelType);
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.Null(result);
+        }
+
+        [Theory]
+        [InlineData(typeof(IFormFile))]
+        [InlineData(typeof(IFormFile[]))]
+        [InlineData(typeof(IFormFileCollection))]
+        [InlineData(typeof(IEnumerable<IFormFile>))]
+        [InlineData(typeof(Collection<IFormFile>))]
+        public void Create_ForSupportedTypes_ReturnsBinder(Type modelType)
+        {
+            // Arrange
+            var provider = new FormFileModelBinderProvider();
+            var context = new TestModelBinderProviderContext(modelType);
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.IsType<FormFileModelBinder>(result);
+        }
+
+        private class TestClass
+        {
+        }
+    }
+}

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/FormFileModelBinderTest.cs

@@ -11,7 +11,7 @@ using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;
 using Moq;
 using Xunit;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
     public class FormFileModelBinderTest
     {
@@ -108,24 +108,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             Assert.Equal("file1.txt", file.FileName);
         }
 
-        [Theory]
-        [InlineData(typeof(string))]
-        [InlineData(typeof(IEnumerable<string>))]
-        public async Task FormFileModelBinder_ReturnsNothing_ForUnsupportedDestinationTypes(Type destinationType)
-        {
-            // Arrange
-            var formFiles = GetTwoFiles();
-            var httpContext = GetMockHttpContext(GetMockFormCollection(formFiles));
-            var bindingContext = GetBindingContext(destinationType, httpContext);
-            var binder = new FormFileModelBinder();
-
-            // Act
-            var result = await binder.BindModelResultAsync(bindingContext);
-
-            // Assert
-            Assert.Equal(default(ModelBindingResult), result);
-        }
-
         [Fact]
         public async Task FormFileModelBinder_ReturnsFailedResult_WhenNoFilePosted()
         {
@@ -303,7 +285,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                     {
                         HttpContext = httpContext,
                     },
-                    ModelBinder = new FormFileModelBinder(),
                     MetadataProvider = metadataProvider,
                 },
                 ValidationState = new ValidationStateDictionary(),

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/HeaderModelBinderProviderTest.cs

@@ -0,0 +1,105 @@
+// 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;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    public class HeaderModelBinderProviderTest
+    {
+        public static TheoryData<BindingSource> NonHeaderBindingSources
+        {
+            get
+            {
+                return new TheoryData<BindingSource>()
+                {
+                    BindingSource.Body,
+                    BindingSource.Form,
+                    null,
+                };
+            }
+        }
+
+        [Theory]
+        [MemberData(nameof(NonHeaderBindingSources))]
+        public void Create_WhenBindingSourceIsNotFromHeader_ReturnsNull(BindingSource source)
+        {
+            // Arrange
+            var provider = new HeaderModelBinderProvider();
+
+            var context = new TestModelBinderProviderContext(typeof(string));
+            context.BindingInfo.BindingSource = source;
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.Null(result);
+        }
+
+        [Fact]
+        public void Create_WhenBindingSourceIsFromHeader_ReturnsBinder()
+        {
+            // Arrange
+            var provider = new HeaderModelBinderProvider();
+
+            var context = new TestModelBinderProviderContext(typeof(string));
+            context.BindingInfo.BindingSource = BindingSource.Header;
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.IsType<HeaderModelBinder>(result);
+        }
+
+        [Theory]
+        [InlineData(typeof(string))]
+        [InlineData(typeof(IEnumerable<string>))]
+        [InlineData(typeof(string[]))]
+        [InlineData(typeof(Collection<string>))]
+        public void Create_WhenModelTypeIsSupportedType_ReturnsBinder(Type modelType)
+        {
+            // Arrange
+            var provider = new HeaderModelBinderProvider();
+
+            var context = new TestModelBinderProviderContext(modelType);
+            context.BindingInfo.BindingSource = BindingSource.Header;
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.IsType<HeaderModelBinder>(result);
+        }
+
+        [Theory]
+        [InlineData(typeof(Dictionary<int, string>))]
+        [InlineData(typeof(Collection<int>))]
+        [InlineData(typeof(Person))]
+        public void Create_WhenModelTypeIsUnsupportedType_ReturnsNull(Type modelType)
+        {
+            // Arrange
+            var provider = new HeaderModelBinderProvider();
+
+            var context = new TestModelBinderProviderContext(modelType);
+            context.BindingInfo.BindingSource = BindingSource.Header;
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.Null(result);
+        }
+
+        private class Person
+        {
+            public string Name { get; set; }
+
+            public int Age { get; set; }
+        }
+    }
+}

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/HeaderModelBinderTests.cs

@@ -7,7 +7,7 @@ using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http.Internal;
 using Xunit;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
     public class HeaderModelBinderTests
     {
@@ -101,50 +101,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
             Assert.Equal(headerValue.Split(','), result.Model as IEnumerable<string>);
         }
 
-        [Fact]
-        public async Task HeaderBinder_ReturnsNothing_ForNullBindingSource()
-        {
-            // Arrange
-            var type = typeof(string);
-            var header = "User-Agent";
-            var headerValue = "UnitTest";
-
-            var binder = new HeaderModelBinder();
-            var modelBindingContext = GetBindingContext(type);
-            modelBindingContext.BindingSource = null;
-
-            modelBindingContext.FieldName = header;
-            modelBindingContext.OperationBindingContext.HttpContext.Request.Headers.Add(header, new[] { headerValue });
-
-            // Act
-            var result = await binder.BindModelResultAsync(modelBindingContext);
-
-            // Assert
-            Assert.Equal(default(ModelBindingResult), result);
-        }
-
-        [Fact]
-        public async Task HeaderBinder_ReturnsNothing_ForNonHeaderBindingSource()
-        {
-            // Arrange
-            var type = typeof(string);
-            var header = "User-Agent";
-            var headerValue = "UnitTest";
-
-            var binder = new HeaderModelBinder();
-            var modelBindingContext = GetBindingContext(type);
-            modelBindingContext.BindingSource = BindingSource.Body;
-
-            modelBindingContext.FieldName = header;
-            modelBindingContext.OperationBindingContext.HttpContext.Request.Headers.Add(header, new[] { headerValue });
-
-            // Act
-            var result = await binder.BindModelResultAsync(modelBindingContext);
-
-            // Assert
-            Assert.Equal(default(ModelBindingResult), result);
-        }
-
         [Fact]
         public async Task HeaderBinder_ReturnsFailedResult_ForReadOnlyDestination()
         {
@@ -227,7 +183,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
                     {
                         HttpContext = new DefaultHttpContext(),
                     },
-                    ModelBinder = new HeaderModelBinder(),
                     MetadataProvider = metadataProvider,
                 },
                 BinderModelName = modelMetadata.BinderModelName,

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/KeyValuePairModelBinderProviderTest.cs

@@ -0,0 +1,66 @@
+// 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;
+using System.Collections.Generic;
+using Moq;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    public class KeyValuePairModelBinderProviderTest
+    {
+        [Theory]
+        [InlineData(typeof(object))]
+        [InlineData(typeof(Person))]
+        [InlineData(typeof(KeyValuePair<string, int>?))]
+        [InlineData(typeof(KeyValuePair<string, int>[]))]
+        public void Create_ForNonKeyValuePair_ReturnsNull(Type modelType)
+        {
+            // Arrange
+            var provider = new KeyValuePairModelBinderProvider();
+
+            var context = new TestModelBinderProviderContext(modelType);
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.Null(result);
+        }
+
+        [Fact]
+        public void Create_ForKeyValuePair_ReturnsBinder()
+        {
+            // Arrange
+            var provider = new KeyValuePairModelBinderProvider();
+
+            var context = new TestModelBinderProviderContext(typeof(KeyValuePair<string, int>));
+            context.OnCreatingBinder(m =>
+            {
+                if (m.ModelType == typeof(string) || m.ModelType == typeof(int))
+                {
+                    return Mock.Of<IModelBinder>();
+                }
+                else
+                {
+                    Assert.False(true, "Not the right model type");
+                    return null;
+                }
+            });
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.IsType<KeyValuePairModelBinder<string, int>>(result);
+        }
+
+        private class Person
+        {
+            public string Name { get; set; }
+
+            public int Age { get; set; }
+        }
+    }
+}

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/KeyValuePairModelBinderTest.cs

@@ -7,11 +7,9 @@ using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http.Internal;
 using Microsoft.AspNetCore.Mvc.DataAnnotations;
 using Microsoft.AspNetCore.Mvc.DataAnnotations.Internal;
-using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;
-using Moq;
 using Xunit;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
     public class KeyValuePairModelBinderTest
     {
@@ -22,8 +20,8 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
             var valueProvider = new SimpleValueProvider();
 
             // Create string binder to create the value but not the key.
-            var bindingContext = GetBindingContext(valueProvider, CreateStringBinder());
+            var bindingContext = GetBindingContext(valueProvider, typeof(KeyValuePair<int, string>));
-            var binder = new KeyValuePairModelBinder<int, string>();
+            var binder = new KeyValuePairModelBinder<int, string>(CreateIntBinder(false), CreateStringBinder());
 
             // Act
             var result = await binder.BindModelResultAsync(bindingContext);
@@ -44,8 +42,8 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
             var valueProvider = new SimpleValueProvider();
 
             // Create int binder to create the value but not the key.
-            var bindingContext = GetBindingContext(valueProvider, CreateIntBinder());
+            var bindingContext = GetBindingContext(valueProvider, typeof(KeyValuePair<int, string>));
-            var binder = new KeyValuePairModelBinder<int, string>();
+            var binder = new KeyValuePairModelBinder<int, string>(CreateIntBinder(), CreateStringBinder(false));
             
             // Act
             var result = await binder.BindModelResultAsync(bindingContext);
@@ -67,11 +65,8 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
             var valueProvider = new SimpleValueProvider();
 
             // Create int binder to create the value but not the key.
-            var bindingContext = GetBindingContext(valueProvider);
+            var bindingContext = GetBindingContext(valueProvider, typeof(KeyValuePair<int, string>));
-            var mockBinder = new StubModelBinder();
+            var binder = new KeyValuePairModelBinder<int, string>(CreateIntBinder(false), CreateStringBinder(false));
-
-            bindingContext.OperationBindingContext.ModelBinder = mockBinder;
-            var binder = new KeyValuePairModelBinder<int, string>();
 
             // Act
             var result = await binder.BindModelResultAsync(bindingContext);
@@ -86,11 +81,10 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
         public async Task BindModel_SubBindingSucceeds()
         {
             // Arrange
-            var innerBinder = new CompositeModelBinder(new[] { CreateStringBinder(), CreateIntBinder() });
             var valueProvider = new SimpleValueProvider();
-            var bindingContext = GetBindingContext(valueProvider, innerBinder);
 
-            var binder = new KeyValuePairModelBinder<int, string>();
+            var bindingContext = GetBindingContext(valueProvider, typeof(KeyValuePair<int, string>));
+            var binder = new KeyValuePairModelBinder<int, string>(CreateIntBinder(), CreateStringBinder());
 
             // Act
             var result = await binder.BindModelResultAsync(bindingContext);
@@ -124,12 +118,15 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
                 Assert.Equal("someName.key", context.ModelName);
                 return innerResult;
             });
-            var bindingContext = GetBindingContext(new SimpleValueProvider(), innerBinder);
 
-            var binder = new KeyValuePairModelBinder<int, string>();
+            var valueProvider = new SimpleValueProvider();
+
+            var bindingContext = GetBindingContext(valueProvider, typeof(KeyValuePair<int, string>));
+            var binder = new KeyValuePairModelBinder<int, string>(innerBinder, innerBinder);
 
             // Act
-            var result = await binder.TryBindStrongModel<int>(bindingContext, "key");
+            var result = await binder.TryBindStrongModel<int>(bindingContext, innerBinder, "key");
+
             // Assert
             Assert.Equal(innerResult.Value, result);
             Assert.Empty(bindingContext.ModelState);
@@ -139,7 +136,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
         public async Task KeyValuePairModelBinder_CreatesEmptyCollection_IfIsTopLevelObject()
         {
             // Arrange
-            var binder = new KeyValuePairModelBinder<string, string>();
+            var binder = new KeyValuePairModelBinder<string, string>(new SimpleTypeModelBinder(), new SimpleTypeModelBinder());
 
             var context = CreateContext();
             context.IsTopLevelObject = true;
@@ -170,7 +167,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
         public async Task KeyValuePairModelBinder_DoesNotCreateCollection_IfNotIsTopLevelObject(string prefix)
         {
             // Arrange
-            var binder = new KeyValuePairModelBinder<string, string>();
+            var binder = new KeyValuePairModelBinder<string, string>(new SimpleTypeModelBinder(), new SimpleTypeModelBinder());
 
             var context = CreateContext();
             context.ModelName = ModelNames.CreatePropertyModelName(prefix, "KeyValuePairProperty");
@@ -200,7 +197,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
                         HttpContext = new DefaultHttpContext(),
                     },
                     MetadataProvider = new TestModelMetadataProvider(),
-                    ModelBinder = new SimpleTypeModelBinder(),
                 },
                 ModelState = new ModelStateDictionary(),
             };
@@ -210,20 +206,17 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
 
         private static DefaultModelBindingContext GetBindingContext(
             IValueProvider valueProvider,
-            IModelBinder innerBinder = null,
+            Type keyValuePairType)
-            Type keyValuePairType = null)
         {
             var metataProvider = new EmptyModelMetadataProvider();
             var bindingContext = new DefaultModelBindingContext
             {
-                ModelMetadata = metataProvider.GetMetadataForType(
+                ModelMetadata = metataProvider.GetMetadataForType(keyValuePairType),
-                    keyValuePairType ?? typeof(KeyValuePair<int, string>)),
                 ModelName = "someName",
                 ModelState = new ModelStateDictionary(),
                 ValueProvider = valueProvider,
                 OperationBindingContext = new OperationBindingContext
                 {
-                    ModelBinder = innerBinder ?? CreateIntBinder(),
                     MetadataProvider = metataProvider,
                     ValidatorProvider = new DataAnnotationsModelValidatorProvider(
                         new ValidationAttributeAdapterProvider(),
@@ -234,11 +227,11 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
             return bindingContext;
         }
 
-        private static IModelBinder CreateIntBinder()
+        private static IModelBinder CreateIntBinder(bool success = true)
         {
             var mockIntBinder = new StubModelBinder(mbc =>
             {
-                if (mbc.ModelType == typeof(int))
+                if (mbc.ModelType == typeof(int) && success)
                 {
                     var model = 42;
                     return ModelBindingResult.Success(mbc.ModelName, model);
@@ -248,11 +241,11 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
             return mockIntBinder;
         }
 
-        private static IModelBinder CreateStringBinder()
+        private static IModelBinder CreateStringBinder(bool success = true)
         {
             return new StubModelBinder(mbc =>
             {
-                if (mbc.ModelType == typeof(string))
+                if (mbc.ModelType == typeof(string) && success)
                 {
                     var model = "some-value";
                     return ModelBindingResult.Success(mbc.ModelName, model);

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/ServicesModelBinderProviderTest.cs

@@ -0,0 +1,60 @@
+// 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 Xunit;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    public class ServicesModelBinderProviderTest
+    {
+        public static TheoryData<BindingSource> NonServicesBindingSources
+        {
+            get
+            {
+                return new TheoryData<BindingSource>()
+                {
+                    BindingSource.Header,
+                    BindingSource.Form,
+                    null,
+                };
+            }
+        }
+
+        [Theory]
+        [MemberData(nameof(NonServicesBindingSources))]
+        public void Create_WhenBindingSourceIsNotFromServices_ReturnsNull(BindingSource source)
+        {
+            // Arrange
+            var provider = new ServicesModelBinderProvider();
+
+            var context = new TestModelBinderProviderContext(typeof(IPersonService));
+            context.BindingInfo.BindingSource = source;
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.Null(result);
+        }
+
+        [Fact]
+        public void Create_WhenBindingSourceIsFromServices_ReturnsBinder()
+        {
+            // Arrange
+            var provider = new ServicesModelBinderProvider();
+
+            var context = new TestModelBinderProviderContext(typeof(IPersonService));
+            context.BindingInfo.BindingSource = BindingSource.Services;
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.IsType<ServicesModelBinder>(result);
+        }
+
+        private class IPersonService
+        {
+        }
+    }
+}

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/ServicesModelBinderTest.cs

@@ -8,7 +8,7 @@ using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;
 using Microsoft.Extensions.DependencyInjection;
 using Xunit;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
     public class ServicesModelBinderTest
     {
@@ -36,40 +36,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             Assert.Null(entry.Metadata);
         }
 
-        [Fact]
-        public async Task ServiceModelBinder_ReturnsNothing_ForNullBindingSource()
-        {
-            // Arrange
-            var type = typeof(IService);
-
-            var binder = new ServicesModelBinder();
-            var modelBindingContext = GetBindingContext(type);
-            modelBindingContext.BindingSource = null;
-
-            // Act
-            var result = await binder.BindModelResultAsync(modelBindingContext);
-
-            // Assert
-            Assert.Equal(default(ModelBindingResult), result);
-        }
-
-        [Fact]
-        public async Task ServiceModelBinder_ReturnsNothing_ForNonServiceBindingSource()
-        {
-            // Arrange
-            var type = typeof(IService);
-
-            var binder = new ServicesModelBinder();
-            var modelBindingContext = GetBindingContext(type);
-            modelBindingContext.BindingSource = BindingSource.Body;
-
-            // Act
-            var result = await binder.BindModelResultAsync(modelBindingContext);
-
-            // Assert
-            Assert.Equal(default(ModelBindingResult), result);
-        }
-
         private static DefaultModelBindingContext GetBindingContext(Type modelType)
         {
             var metadataProvider = new TestModelMetadataProvider();
@@ -95,7 +61,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                             RequestServices = services.BuildServiceProvider(),
                         }
                     },
-                    ModelBinder = new HeaderModelBinder(),
                     MetadataProvider = metadataProvider,
                 },
                 BinderModelName = modelMetadata.BinderModelName,

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/SimpleTypeModelBinderProviderTest.cs

@@ -0,0 +1,53 @@
+// 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;
+using System.Collections.Generic;
+using System.Globalization;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
+{
+    public class SimpleTypeModelBinderProviderTest
+    {
+        [Theory]
+        [InlineData(typeof(object))]
+        [InlineData(typeof(Calendar))]
+        [InlineData(typeof(TestClass))]
+        [InlineData(typeof(List<int>))]
+        public void Create_ForCollectionOrComplexTypes_ReturnsNull(Type modelType)
+        {
+            // Arrange
+            var provider = new SimpleTypeModelBinderProvider();
+            var context = new TestModelBinderProviderContext(modelType);
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.Null(result);
+        }
+
+        [Theory]
+        [InlineData(typeof(int))]
+        [InlineData(typeof(string))]
+        [InlineData(typeof(DateTime))]
+        [InlineData(typeof(DateTime?))]
+        public void Create_ForSimpleTypes_ReturnsBinder(Type modelType)
+        {
+            // Arrange
+            var provider = new SimpleTypeModelBinderProvider();
+            var context = new TestModelBinderProviderContext(modelType);
+
+            // Act
+            var result = provider.GetBinder(context);
+
+            // Assert
+            Assert.IsType<SimpleTypeModelBinder>(result);
+        }
+
+        private class TestClass
+        {
+        }
+    }
+}

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/SimpleTypeModelBinderTest.cs

@@ -7,32 +7,10 @@ using System.Threading.Tasks;
 using Microsoft.AspNetCore.Testing;
 using Xunit;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
+namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
     public class SimpleTypeModelBinderTest
     {
-        [Theory]
-        [InlineData(typeof(object))]
-        [InlineData(typeof(Calendar))]
-        [InlineData(typeof(TestClass))]
-        public async Task BindModel_ReturnsNothing_IfTypeCannotBeConverted(Type destinationType)
-        {
-            // Arrange
-            var bindingContext = GetBindingContext(destinationType);
-            bindingContext.ValueProvider = new SimpleValueProvider
-            {
-                { "theModelName", "some-value" }
-            };
-
-            var binder = new SimpleTypeModelBinder();
-
-            // Act
-            var result = await binder.BindModelResultAsync(bindingContext);
-
-            // Assert
-            Assert.Equal(default(ModelBindingResult), result);
-        }
-
         public static TheoryData<Type> ConvertableTypeData
         {
             get
@@ -134,7 +112,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
         }
 
         [Fact]
-        public async Task BindModel_NullValueProviderResult_ReturnsNull()
+        public async Task BindModel_EmptyValueProviderResult_ReturnsFailed()
         {
             // Arrange
             var bindingContext = GetBindingContext(typeof(int));
@@ -144,7 +122,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
             var result = await binder.BindModelResultAsync(bindingContext);
 
             // Assert
-            Assert.Equal(default(ModelBindingResult), result);
+            Assert.Equal(ModelBindingResult.Failed("theModelName"), result);
             Assert.Empty(bindingContext.ModelState);
         }
 

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/CompositeModelBinderTest.cs

@@ -1,532 +0,0 @@
-// 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;
-using System.Collections.Generic;
-using System.ComponentModel.DataAnnotations;
-using System.Threading.Tasks;
-using Microsoft.AspNetCore.Mvc.ModelBinding.Metadata;
-using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;
-using Xunit;
-
-namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
-{
-    public class CompositeModelBinderTest
-    {
-        [Fact]
-        public async Task BindModel_SuccessfulBind_ReturnsModel()
-        {
-            // Arrange
-            var bindingContext = new DefaultModelBindingContext
-            {
-                FallbackToEmptyPrefix = true,
-                ModelMetadata = new EmptyModelMetadataProvider().GetMetadataForType(typeof(int)),
-                ModelName = "someName",
-                ModelState = new ModelStateDictionary(),
-                OperationBindingContext = new OperationBindingContext(),
-                ValueProvider = new SimpleValueProvider
-                {
-                    { "someName", "dummyValue" }
-                },
-                ValidationState = new ValidationStateDictionary(),
-                FieldName = "someName",
-            };
-
-            var mockIntBinder = new StubModelBinder(context =>
-            {
-                Assert.Same(bindingContext.ModelMetadata, context.ModelMetadata);
-                Assert.Equal("someName", context.ModelName);
-                Assert.Same(bindingContext.ValueProvider, context.ValueProvider);
-
-                context.Result = ModelBindingResult.Success("someName", 42);
-            });
-            var shimBinder = CreateCompositeBinder(mockIntBinder);
-
-            // Act
-            var result = await shimBinder.BindModelResultAsync(bindingContext);
-
-            // Assert
-            Assert.NotEqual(default(ModelBindingResult), result);
-            Assert.True(result.IsModelSet);
-            Assert.Equal(42, result.Model);
-        }
-
-        [Fact]
-        public async Task BindModel_SuccessfulBind_SetsValidationStateAtTopLevel()
-        {
-            // Arrange
-            var bindingContext = new DefaultModelBindingContext
-            {
-                FallbackToEmptyPrefix = true,
-                IsTopLevelObject = true,
-                ModelMetadata = new EmptyModelMetadataProvider().GetMetadataForType(typeof(int)),
-                ModelName = "someName",
-                ModelState = new ModelStateDictionary(),
-                OperationBindingContext = new OperationBindingContext(),
-                ValueProvider = new SimpleValueProvider
-                {
-                    { "someName", "dummyValue" }
-                },
-                ValidationState = new ValidationStateDictionary(),
-                FieldName = "someName",
-            };
-
-            var mockIntBinder = new StubModelBinder(context =>
-            {
-                Assert.Same(bindingContext.ModelMetadata, context.ModelMetadata);
-                Assert.Equal("someName", context.ModelName);
-                Assert.Same(bindingContext.ValueProvider, context.ValueProvider);
-
-                context.Result = ModelBindingResult.Success("someName", 42);
-            });
-            var shimBinder = CreateCompositeBinder(mockIntBinder);
-
-            // Act
-            var result = await shimBinder.BindModelResultAsync(bindingContext);
-
-            // Assert
-            Assert.NotEqual(default(ModelBindingResult), result);
-            Assert.True(result.IsModelSet);
-            Assert.Equal(42, result.Model);
-
-            Assert.Contains(result.Model, bindingContext.ValidationState.Keys);
-            var entry = bindingContext.ValidationState[result.Model];
-            Assert.Equal("someName", entry.Key);
-            Assert.Same(bindingContext.ModelMetadata, entry.Metadata);
-        }
-
-        [Fact]
-        public async Task BindModel_SuccessfulBind_DoesNotSetValidationState_WhenNotTopLevel()
-        {
-            // Arrange
-            var bindingContext = new DefaultModelBindingContext
-            {
-                FallbackToEmptyPrefix = true,
-                ModelMetadata = new EmptyModelMetadataProvider().GetMetadataForType(typeof(int)),
-                ModelName = "someName",
-                ModelState = new ModelStateDictionary(),
-                OperationBindingContext = new OperationBindingContext(),
-                ValueProvider = new SimpleValueProvider
-                {
-                    { "someName", "dummyValue" }
-                },
-                ValidationState = new ValidationStateDictionary(),
-                FieldName = "someName",
-            };
-
-            var mockIntBinder = new StubModelBinder(context =>
-            {
-                Assert.Same(bindingContext.ModelMetadata, context.ModelMetadata);
-                Assert.Equal("someName", context.ModelName);
-                Assert.Same(bindingContext.ValueProvider, context.ValueProvider);
-
-                context.Result = ModelBindingResult.Success("someName", 42);
-            });
-            var shimBinder = CreateCompositeBinder(mockIntBinder);
-
-            // Act
-            var result = await shimBinder.BindModelResultAsync(bindingContext);
-
-            // Assert
-            Assert.NotEqual(default(ModelBindingResult), result);
-            Assert.True(result.IsModelSet);
-            Assert.Equal(42, result.Model);
-
-            Assert.Empty(bindingContext.ValidationState);
-        }
-
-        [Fact]
-        public async Task BindModel_SuccessfulBind_ComplexTypeFallback_ReturnsModel()
-        {
-            // Arrange
-            var expectedModel = new List<int> { 1, 2, 3, 4, 5 };
-
-            var bindingContext = new DefaultModelBindingContext
-            {
-                FallbackToEmptyPrefix = true,
-                IsTopLevelObject = true,
-                ModelMetadata = new EmptyModelMetadataProvider().GetMetadataForType(typeof(List<int>)),
-                ModelName = "someName",
-                ModelState = new ModelStateDictionary(),
-                OperationBindingContext = new OperationBindingContext(),
-                ValueProvider = new SimpleValueProvider
-                {
-                    { "someOtherName", "dummyValue" }
-                },
-                ValidationState = new ValidationStateDictionary(),
-                FieldName = "someName",
-            };
-
-            var mockIntBinder = new StubModelBinder(mbc =>
-            {
-                if (!string.IsNullOrEmpty(mbc.ModelName))
-                {
-                    return;
-                }
-
-                Assert.Same(bindingContext.ModelMetadata, mbc.ModelMetadata);
-                Assert.Equal("", mbc.ModelName);
-                Assert.Same(bindingContext.ValueProvider, mbc.ValueProvider);
-
-                mbc.Result = ModelBindingResult.Success(string.Empty, expectedModel);
-            });
-
-            var shimBinder = CreateCompositeBinder(mockIntBinder);
-
-            // Act
-            var result = await shimBinder.BindModelResultAsync(bindingContext);
-
-            // Assert
-            Assert.NotEqual(default(ModelBindingResult), result);
-            Assert.True(result.IsModelSet);
-            Assert.Equal(string.Empty, result.Key);
-            Assert.Equal(expectedModel, result.Model);
-        }
-
-        [Fact]
-        public async Task ModelBinder_ReturnsNothing_IfBinderMatchesButDoesNotSetModel()
-        {
-            // Arrange
-            var bindingContext = new DefaultModelBindingContext
-            {
-                FallbackToEmptyPrefix = true,
-                ModelMetadata = new EmptyModelMetadataProvider().GetMetadataForType(typeof(List<int>)),
-                ModelName = "someName",
-                ModelState = new ModelStateDictionary(),
-                OperationBindingContext = new OperationBindingContext(),
-                ValueProvider = new SimpleValueProvider
-                {
-                    { "someOtherName", "dummyValue" }
-                },
-                FieldName = "someName",
-            };
-
-            var mockIntBinder = new StubModelBinder(context =>
-            {
-                context.Result = ModelBindingResult.Failed("someName");
-            });
-
-            var composite = CreateCompositeBinder(mockIntBinder);
-
-            // Act
-            var result = await composite.BindModelResultAsync(bindingContext);
-
-            // Assert
-            Assert.Equal(default(ModelBindingResult), result);
-        }
-
-        [Fact]
-        public async Task ModelBinder_DoesNotFallBackToEmpty_IfFallbackToEmptyPrefixFalse()
-        {
-            // Arrange
-            var bindingContext = new DefaultModelBindingContext
-            {
-                FallbackToEmptyPrefix = false,
-                ModelMetadata = new EmptyModelMetadataProvider().GetMetadataForType(typeof(List<int>)),
-                ModelName = "someName",
-                ModelState = new ModelStateDictionary(),
-                OperationBindingContext = new OperationBindingContext(),
-                ValueProvider = new SimpleValueProvider
-                {
-                    { "someOtherName", "dummyValue" }
-                },
-                FieldName = "someName",
-            };
-
-            var mockIntBinder = new StubModelBinder(context =>
-            {
-                Assert.Equal("someName", context.ModelName);
-                context.Result = ModelBindingResult.Failed("someName");
-            });
-
-            var composite = CreateCompositeBinder(mockIntBinder);
-
-            // Act & Assert
-            var result = await composite.BindModelResultAsync(bindingContext);
-            Assert.Equal(1, mockIntBinder.BindModelCount);
-        }
-
-        [Fact]
-        public async Task ModelBinder_DoesNotFallBackToEmpty_IfErrorsAreAdded()
-        {
-            // Arrange
-            var bindingContext = new DefaultModelBindingContext
-            {
-                FallbackToEmptyPrefix = false,
-                ModelMetadata = new EmptyModelMetadataProvider().GetMetadataForType(typeof(List<int>)),
-                ModelName = "someName",
-                ModelState = new ModelStateDictionary(),
-                OperationBindingContext = new OperationBindingContext(),
-                ValueProvider = new SimpleValueProvider
-                {
-                    { "someOtherName", "dummyValue" }
-                },
-                FieldName = "someName",
-            };
-
-            var mockIntBinder = new StubModelBinder(context =>
-            {
-                Assert.Equal("someName", context.ModelName);
-                context.ModelState.AddModelError(context.ModelName, "this is an error message");
-                context.Result = ModelBindingResult.Failed("someName");
-            });
-
-            var composite = CreateCompositeBinder(mockIntBinder);
-
-            // Act & Assert
-            var result = await composite.BindModelResultAsync(bindingContext);
-            Assert.Equal(1, mockIntBinder.BindModelCount);
-        }
-
-        [Fact]
-        public async Task ModelBinder_ReturnsNonEmptyResult_SetsNullValue_SetsModelStateKey()
-        {
-            // Arrange
-            var bindingContext = new DefaultModelBindingContext
-            {
-                FallbackToEmptyPrefix = true,
-                ModelMetadata = new EmptyModelMetadataProvider().GetMetadataForType(typeof(List<int>)),
-                ModelName = "someName",
-                ModelState = new ModelStateDictionary(),
-                OperationBindingContext = new OperationBindingContext(),
-                ValueProvider = new SimpleValueProvider
-                {
-                    { "someOtherName", "dummyValue" }
-                },
-                FieldName = "someName",
-            };
-
-            var mockIntBinder = new StubModelBinder(context =>
-            {
-                context.Result = ModelBindingResult.Success("someName", model: null);
-            });
-
-            var composite = CreateCompositeBinder(mockIntBinder);
-
-            // Act
-            var result = await composite.BindModelResultAsync(bindingContext);
-
-            // Assert
-            Assert.NotEqual(default(ModelBindingResult), result);
-            Assert.True(result.IsModelSet);
-            Assert.Equal("someName", result.Key);
-            Assert.Null(result.Model);
-        }
-
-        [Fact]
-        public async Task BindModel_UnsuccessfulBind_SimpleTypeNoFallback_ReturnsNothing()
-        {
-            // Arrange
-            var shimBinder = CreateCompositeBinder(new StubModelBinder());
-
-            var bindingContext = new DefaultModelBindingContext
-            {
-                FallbackToEmptyPrefix = true,
-                ModelMetadata = new EmptyModelMetadataProvider().GetMetadataForType(typeof(int)),
-                ModelState = new ModelStateDictionary(),
-                OperationBindingContext = new OperationBindingContext(),
-                ValueProvider = new SimpleValueProvider(),
-                FieldName = "test-field",
-            };
-
-            // Act
-            var result = await shimBinder.BindModelResultAsync(bindingContext);
-
-            // Assert
-            Assert.Equal(default(ModelBindingResult), result);
-        }
-
-        [Fact]
-        public async Task BindModel_WithDefaultBinders_BindsSimpleType()
-        {
-            // Arrange
-            var binder = CreateBinderWithDefaults();
-
-            var valueProvider = new SimpleValueProvider
-            {
-                { "firstName", "firstName-value"},
-                { "lastName", "lastName-value"}
-            };
-            var bindingContext = CreateBindingContext(binder, valueProvider, typeof(SimplePropertiesModel));
-
-            // Act
-            var result = await binder.BindModelResultAsync(bindingContext);
-
-            // Assert
-            Assert.NotEqual(default(ModelBindingResult), result);
-            var model = Assert.IsType<SimplePropertiesModel>(result.Model);
-            Assert.Equal("firstName-value", model.FirstName);
-            Assert.Equal("lastName-value", model.LastName);
-        }
-
-        [Fact]
-        public async Task BindModel_WithDefaultBinders_BindsComplexType()
-        {
-            // Arrange
-            var binder = CreateBinderWithDefaults();
-
-            var valueProvider = new SimpleValueProvider
-            {
-                { "firstName", "firstName-value"},
-                { "lastName", "lastName-value"},
-                { "friends[0].firstName", "first-friend"},
-                { "friends[0].age", "40"},
-                { "friends[0].friends[0].firstname", "nested friend"},
-                { "friends[1].firstName", "some other"},
-                { "friends[1].lastName", "name"},
-                { "resume", "4+mFeTp3tPF=" }
-            };
-
-            var bindingContext = CreateBindingContext(binder, valueProvider, typeof(Person));
-
-            // Act
-            var result = await binder.BindModelResultAsync(bindingContext);
-
-            // Assert
-            Assert.NotEqual(default(ModelBindingResult), result);
-            var model = Assert.IsType<Person>(result.Model);
-            Assert.Equal("firstName-value", model.FirstName);
-            Assert.Equal("lastName-value", model.LastName);
-            Assert.Equal(2, model.Friends.Count);
-            Assert.Equal("first-friend", model.Friends[0].FirstName);
-            Assert.Equal(40, model.Friends[0].Age);
-            var nestedFriend = Assert.Single(model.Friends[0].Friends);
-            Assert.Equal("nested friend", nestedFriend.FirstName);
-            Assert.Equal("some other", model.Friends[1].FirstName);
-            Assert.Equal("name", model.Friends[1].LastName);
-            Assert.Equal(new byte[] { 227, 233, 133, 121, 58, 119, 180, 241 }, model.Resume);
-        }
-
-        [Fact]
-        public async Task BindModel_DoesNotAddAValidationNode_IfModelIsNotSet()
-        {
-            // Arrange
-            var valueProvider = new SimpleValueProvider();
-            var mockBinder = new StubModelBinder(ModelBindingResult.Failed("someName"));
-
-            var binder = CreateCompositeBinder(mockBinder);
-            var bindingContext = CreateBindingContext(binder, valueProvider, typeof(SimplePropertiesModel));
-
-            // Act
-            var result = await binder.BindModelResultAsync(bindingContext);
-
-            // Assert
-            Assert.Equal(default(ModelBindingResult), result);
-        }
-
-        [Fact]
-        public async Task BindModel_DoesNotAddAValidationNode_IfModelBindingResultIsNothing()
-        {
-            // Arrange
-            var mockBinder = new StubModelBinder();
-            var binder = CreateCompositeBinder(mockBinder);
-            var valueProvider = new SimpleValueProvider();
-            var bindingContext = CreateBindingContext(binder, valueProvider, typeof(SimplePropertiesModel));
-
-            // Act
-            var result = await binder.BindModelResultAsync(bindingContext);
-
-            // Assert
-            Assert.Equal(default(ModelBindingResult), result);
-        }
-
-        [Fact]
-        public async Task BindModel_UsesTheValidationNodeOnModelBindingResult_IfPresent()
-        {
-            // Arrange
-            var valueProvider = new SimpleValueProvider();
-
-            var mockBinder = new StubModelBinder(ModelBindingResult.Success("someName", 42));
-
-            var binder = CreateCompositeBinder(mockBinder);
-            var bindingContext = CreateBindingContext(binder, valueProvider, typeof(SimplePropertiesModel));
-
-            // Act
-            var result = await binder.BindModelResultAsync(bindingContext);
-
-            // Assert
-            Assert.NotEqual(default(ModelBindingResult), result);
-            Assert.True(result.IsModelSet);
-        }
-
-        private static DefaultModelBindingContext CreateBindingContext(
-            IModelBinder binder,
-            IValueProvider valueProvider,
-            Type type)
-        {
-            var metadataProvider = TestModelMetadataProvider.CreateDefaultProvider();
-            var bindingContext = new DefaultModelBindingContext
-            {
-                FallbackToEmptyPrefix = true,
-                IsTopLevelObject = true,
-                ModelMetadata = metadataProvider.GetMetadataForType(type),
-                ModelName = "parameter",
-                FieldName = "parameter",
-                ModelState = new ModelStateDictionary(),
-                ValueProvider = valueProvider,
-                OperationBindingContext = new OperationBindingContext
-                {
-                    MetadataProvider = metadataProvider,
-                    ModelBinder = binder,
-                },
-                ValidationState = new ValidationStateDictionary(),
-            };
-            return bindingContext;
-        }
-
-        private static CompositeModelBinder CreateBinderWithDefaults()
-        {
-            var binders = new IModelBinder[]
-            {
-                new ByteArrayModelBinder(),
-                new GenericModelBinder(),
-                new SimpleTypeModelBinder(),
-                new MutableObjectModelBinder()
-            };
-
-            var binder = new CompositeModelBinder(binders);
-            return binder;
-        }
-
-        private static CompositeModelBinder CreateCompositeBinder(IModelBinder mockIntBinder)
-        {
-            var shimBinder = new CompositeModelBinder(new[] { mockIntBinder });
-            return shimBinder;
-        }
-
-        private class SimplePropertiesModel
-        {
-            public string FirstName { get; set; }
-            public string LastName { get; set; }
-        }
-
-        private sealed class Person
-        {
-            public string FirstName { get; set; }
-
-            public string LastName { get; set; }
-
-            public int Age { get; set; }
-
-            public List<Person> Friends { get; set; }
-
-            public byte[] Resume { get; set; }
-        }
-
-        private class User : IValidatableObject
-        {
-            public string Password { get; set; }
-
-            [Compare("Password")]
-            public string ConfirmPassword { get; set; }
-
-            public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
-            {
-                if (Password == "password")
-                {
-                    yield return new ValidationResult("Password does not meet complexity requirements.");
-                }
-            }
-        }
-    }
-}

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/DefaultModelBindingContextTest.cs

@@ -2,9 +2,13 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Collections.Generic;
 using System.Diagnostics;
+using System.Globalization;
 using System.Threading.Tasks;
-using Microsoft.AspNetCore.Mvc.ModelBinding.Test;
+using Microsoft.AspNetCore.Http.Internal;
+using Microsoft.AspNetCore.Routing;
+using Microsoft.Extensions.Primitives;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Mvc.ModelBinding
@@ -37,7 +41,6 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
 
             // Act
             var originalBinderModelName = bindingContext.BinderModelName;
-            var originalBinderType = bindingContext.BinderType;
             var originalBindingSource = bindingContext.BindingSource;
             var originalModelState = bindingContext.ModelState;
             var originalOperationBindingContext = bindingContext.OperationBindingContext;
@@ -51,9 +54,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
 
             // Assert
             Assert.Same(newModelMetadata.BinderModelName, bindingContext.BinderModelName);
-            Assert.Same(newModelMetadata.BinderType, bindingContext.BinderType);
             Assert.Same(newModelMetadata.BindingSource, bindingContext.BindingSource);
-            Assert.False(bindingContext.FallbackToEmptyPrefix);
             Assert.Equal("fieldName", bindingContext.FieldName);
             Assert.False(bindingContext.IsTopLevelObject);
             Assert.Null(bindingContext.Model);
@@ -66,6 +67,98 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             disposable.Dispose();
         }
 
+        [Fact]
+        public void CreateBindingContext_FiltersValueProviders_ForValueProviderSource()
+        {
+            // Arrange
+            var metadataProvider = new TestModelMetadataProvider();
+
+            var original = CreateDefaultValueProvider();
+            var operationBindingContext = new OperationBindingContext()
+            {
+                ActionContext = new ActionContext(),
+                ValueProvider = original,
+            };
+
+            // Act
+            var context = DefaultModelBindingContext.CreateBindingContext(
+                operationBindingContext,
+                metadataProvider.GetMetadataForType(typeof(object)),
+                new BindingInfo() { BindingSource = BindingSource.Query },
+                "model");
+
+            // Assert
+            Assert.Collection(
+                Assert.IsType<CompositeValueProvider>(context.ValueProvider),
+                vp => Assert.Same(original[1], vp));
+        }
+
+        [Fact]
+        public void EnterNestedScope_FiltersValueProviders_ForValueProviderSource()
+        {
+            // Arrange
+            var metadataProvider = new TestModelMetadataProvider();
+            metadataProvider
+                .ForProperty(typeof(string), nameof(string.Length))
+                .BindingDetails(b => b.BindingSource = BindingSource.Query);
+
+            var original = CreateDefaultValueProvider();
+            var operationBindingContext = new OperationBindingContext()
+            {
+                ActionContext = new ActionContext(),
+                ValueProvider = original,
+            };
+
+            var context = DefaultModelBindingContext.CreateBindingContext(
+                operationBindingContext,
+                metadataProvider.GetMetadataForType(typeof(string)),
+                new BindingInfo(),
+                "model");
+
+            var propertyMetadata = metadataProvider.GetMetadataForProperty(typeof(string), nameof(string.Length));
+
+            // Act
+            context.EnterNestedScope(propertyMetadata, "Length", "Length", model: null);
+
+            // Assert
+            Assert.Collection(
+                Assert.IsType<CompositeValueProvider>(context.ValueProvider),
+                vp => Assert.Same(original[1], vp));
+        }
+
+        [Fact]
+        public void EnterNestedScope_FiltersValueProviders_BasedOnTopLevelValueProviders()
+        {
+            // Arrange
+            var metadataProvider = new TestModelMetadataProvider();
+            metadataProvider
+                .ForProperty(typeof(string), nameof(string.Length))
+                .BindingDetails(b => b.BindingSource = BindingSource.Form);
+
+            var original = CreateDefaultValueProvider();
+            var operationBindingContext = new OperationBindingContext()
+            {
+                ActionContext = new ActionContext(),
+                ValueProvider = original,
+            };
+
+            var context = DefaultModelBindingContext.CreateBindingContext(
+                operationBindingContext,
+                metadataProvider.GetMetadataForType(typeof(string)),
+                new BindingInfo() { BindingSource = BindingSource.Query },
+                "model");
+
+            var propertyMetadata = metadataProvider.GetMetadataForProperty(typeof(string), nameof(string.Length));
+
+            // Act
+            context.EnterNestedScope(propertyMetadata, "Length", "Length", model: null);
+
+            // Assert
+            Assert.Collection(
+                Assert.IsType<CompositeValueProvider>(context.ValueProvider),
+                vp => Assert.Same(original[2], vp));
+        }
+
         [Fact]
         public void ModelTypeAreFedFromModelMetadata()
         {
@@ -79,6 +172,21 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             Assert.Equal(typeof(int), bindingContext.ModelType);
         }
 
+        private static CompositeValueProvider CreateDefaultValueProvider()
+        {
+            var result = new CompositeValueProvider();
+            result.Add(new RouteValueProvider(BindingSource.Path, new RouteValueDictionary()));
+            result.Add(new QueryStringValueProvider(
+                BindingSource.Query,
+                new QueryCollection(),
+                CultureInfo.InvariantCulture));
+            result.Add(new FormValueProvider(
+                BindingSource.Form,
+                new FormCollection(new Dictionary<string, StringValues>()),
+                CultureInfo.CurrentCulture));
+            return result;
+        }
+
         private class TestModelBinder : IModelBinder
         {
             public Task BindModelAsync(ModelBindingContext bindingContext)

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Metadata/ModelBinderAttributeTest.cs

@@ -1,6 +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 Microsoft.AspNetCore.Mvc.ModelBinding.Binders;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Mvc.ModelBinding

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/ModelBinderFactoryTest.cs

@@ -0,0 +1,228 @@
+// 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;
+using Microsoft.AspNetCore.Mvc.ModelBinding.Internal;
+using Moq;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding
+{
+    public class ModelBinderFactoryTest
+    {
+        // No providers => can't create a binder
+        [Fact]
+        public void CreateBinder_Throws_WhenBinderNotCreated()
+        {
+            // Arrange 
+            var metadataProvider = new TestModelMetadataProvider();
+            var options = new TestOptionsManager<MvcOptions>();
+            var factory = new ModelBinderFactory(metadataProvider, options);
+
+            var context = new ModelBinderFactoryContext()
+            {
+                Metadata = metadataProvider.GetMetadataForType(typeof(string)),
+            };
+
+            // Act
+            var exception = Assert.Throws<InvalidOperationException>(() => factory.CreateBinder(context));
+
+            // Assert
+            Assert.Equal(
+                $"Could not create a model binder for model object of type '{typeof(string).FullName}'.",
+                exception.Message);
+        }
+
+        [Fact]
+        public void CreateBinder_CreatesNoOpBinder_WhenPropertyDoesntHaveABinder()
+        {
+            // Arrange 
+            var metadataProvider = new TestModelMetadataProvider();
+
+            // There isn't a provider that can handle WidgetId.
+            var options = new TestOptionsManager<MvcOptions>();
+            options.Value.ModelBinderProviders.Add(new TestModelBinderProvider(c =>
+            {
+                if (c.Metadata.ModelType == typeof(Widget))
+                {
+                    Assert.NotNull(c.CreateBinder(c.Metadata.Properties[nameof(Widget.Id)]));
+                    return Mock.Of<IModelBinder>();
+                }
+
+                return null;
+            }));
+
+            var factory = new ModelBinderFactory(metadataProvider, options);
+
+            var context = new ModelBinderFactoryContext()
+            {
+                Metadata = metadataProvider.GetMetadataForType(typeof(Widget)),
+            };
+
+            // Act
+            var result = factory.CreateBinder(context);
+
+            // Assert
+            Assert.NotNull(result);
+        }
+
+        [Fact]
+        public void CreateBinder_NestedProperties()
+        {
+            // Arrange 
+            var metadataProvider = new TestModelMetadataProvider();
+
+            var options = new TestOptionsManager<MvcOptions>();
+            options.Value.ModelBinderProviders.Add(new TestModelBinderProvider(c =>
+            {
+                if (c.Metadata.ModelType == typeof(Widget))
+                {
+                    Assert.NotNull(c.CreateBinder(c.Metadata.Properties[nameof(Widget.Id)]));
+                    return Mock.Of<IModelBinder>();
+                }
+                else if (c.Metadata.ModelType == typeof(WidgetId))
+                {
+                    return Mock.Of<IModelBinder>();
+                }
+
+                return null;
+            }));
+
+            var factory = new ModelBinderFactory(metadataProvider, options);
+
+            var context = new ModelBinderFactoryContext()
+            {
+                Metadata = metadataProvider.GetMetadataForType(typeof(Widget)),
+            };
+
+            // Act
+            var result = factory.CreateBinder(context);
+
+            // Assert
+            Assert.NotNull(result);
+        }
+
+        [Fact]
+        public void CreateBinder_BreaksCycles()
+        {
+            // Arrange 
+            var metadataProvider = new TestModelMetadataProvider();
+
+            var callCount = 0;
+
+            var options = new TestOptionsManager<MvcOptions>();
+            options.Value.ModelBinderProviders.Add(new TestModelBinderProvider(c =>
+            {
+                var currentCallCount = ++callCount;
+                Assert.Equal(typeof(Employee), c.Metadata.ModelType);
+                var binder = c.CreateBinder(c.Metadata.Properties[nameof(Employee.Manager)]);
+
+                if (currentCallCount == 2)
+                {
+                    Assert.IsType<PlaceholderBinder>(binder);
+                }
+
+                return Mock.Of<IModelBinder>();
+            }));
+
+            var factory = new ModelBinderFactory(metadataProvider, options);
+
+            var context = new ModelBinderFactoryContext()
+            {
+                Metadata = metadataProvider.GetMetadataForType(typeof(Employee)),
+            };
+
+            // Act
+            var result = factory.CreateBinder(context);
+
+            // Assert
+            Assert.NotNull(result);
+        }
+
+        [Fact]
+        public void CreateBinder_DoesNotCache_WhenTokenIsNull()
+        {
+            // Arrange 
+            var metadataProvider = new TestModelMetadataProvider();
+
+            var options = new TestOptionsManager<MvcOptions>();
+            options.Value.ModelBinderProviders.Add(new TestModelBinderProvider(c =>
+            {
+                Assert.Equal(typeof(Employee), c.Metadata.ModelType);
+                return Mock.Of<IModelBinder>();
+            }));
+
+            var factory = new ModelBinderFactory(metadataProvider, options);
+
+            var context = new ModelBinderFactoryContext()
+            {
+                Metadata = metadataProvider.GetMetadataForType(typeof(Employee)),
+            };
+
+            // Act
+            var result1 = factory.CreateBinder(context);
+            var result2 = factory.CreateBinder(context);
+
+            // Assert
+            Assert.NotSame(result1, result2);
+        }
+
+        [Fact]
+        public void CreateBinder_Caches_WhenTokenIsNotNull()
+        {
+            // Arrange 
+            var metadataProvider = new TestModelMetadataProvider();
+
+            var options = new TestOptionsManager<MvcOptions>();
+            options.Value.ModelBinderProviders.Add(new TestModelBinderProvider(c =>
+            {
+                Assert.Equal(typeof(Employee), c.Metadata.ModelType);
+                return Mock.Of<IModelBinder>();
+            }));
+
+            var factory = new ModelBinderFactory(metadataProvider, options);
+
+            var context = new ModelBinderFactoryContext()
+            {
+                Metadata = metadataProvider.GetMetadataForType(typeof(Employee)),
+                CacheToken = new object(),
+            };
+
+            // Act
+            var result1 = factory.CreateBinder(context);
+            var result2 = factory.CreateBinder(context);
+
+            // Assert
+            Assert.Same(result1, result2);
+        }
+
+        private class Widget
+        {
+            public WidgetId Id { get; set; }
+        }
+
+        private class WidgetId
+        {
+        }
+
+        private class Employee
+        {
+            public Employee Manager { get; set; }
+        }
+
+        private class TestModelBinderProvider : IModelBinderProvider
+        {
+            private readonly Func<ModelBinderProviderContext, IModelBinder> _factory;
+
+            public TestModelBinderProvider(Func<ModelBinderProviderContext, IModelBinder> factory)
+            {
+                _factory = factory;
+            }
+
+            public IModelBinder GetBinder(ModelBinderProviderContext context)
+            {
+                return _factory(context);
+            }
+        }
+    }
+}

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/ModelBindingHelperTest.cs

@@ -13,6 +13,7 @@ using Microsoft.AspNetCore.Mvc.DataAnnotations;
 using Microsoft.AspNetCore.Mvc.DataAnnotations.Internal;
 using Microsoft.AspNetCore.Mvc.Formatters;
 using Microsoft.AspNetCore.Mvc.Internal;
+using Microsoft.AspNetCore.Mvc.ModelBinding.Binders;
 using Microsoft.AspNetCore.Mvc.ModelBinding.Test;
 using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;
 using Moq;
@@ -49,7 +50,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 string.Empty,
                 new ActionContext() { HttpContext = new DefaultHttpContext() },
                 metadataProvider,
-                GetCompositeBinder(binder),
+                GetModelBinderFactory(binder),
                 Mock.Of<IValueProvider>(),
                 new List<IInputFormatter>(),
                 new Mock<IObjectModelValidator>(MockBehavior.Strict).Object,
@@ -66,10 +67,10 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             // Arrange
             // Mono issue - https://github.com/aspnet/External/issues/19
             var expectedMessage = PlatformNormalizer.NormalizeContent("The MyProperty field is required.");
-            var binders = new IModelBinder[]
+            var binderProviders = new IModelBinderProvider[]
             {
-                new SimpleTypeModelBinder(),
+                new SimpleTypeModelBinderProvider(),
-                new MutableObjectModelBinder()
+                new ComplexTypeModelBinderProvider(),
             };
 
             var validator = new DataAnnotationsModelValidatorProvider(
@@ -94,7 +95,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 "",
                 actionContext,
                 modelMetadataProvider,
-                GetCompositeBinder(binders),
+                GetModelBinderFactory(binderProviders),
                 valueProvider,
                 new List<IInputFormatter>(),
                 new DefaultObjectValidator(modelMetadataProvider, new ValidatorCache()),
@@ -110,10 +111,10 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         public async Task TryUpdateModel_ReturnsTrue_IfModelBindsAndValidatesSuccessfully()
         {
             // Arrange
-            var binders = new IModelBinder[]
+            var binderProviders = new IModelBinderProvider[]
             {
-                new SimpleTypeModelBinder(),
+                new SimpleTypeModelBinderProvider(),
-                new MutableObjectModelBinder()
+                new ComplexTypeModelBinderProvider(),
             };
 
             var validator = new DataAnnotationsModelValidatorProvider(
@@ -136,7 +137,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 "",
                 new ActionContext() { HttpContext = new DefaultHttpContext() },
                 metadataProvider,
-                GetCompositeBinder(binders),
+                GetModelBinderFactory(binderProviders),
                 valueProvider,
                 new List<IInputFormatter>(),
                 new DefaultObjectValidator(metadataProvider, new ValidatorCache()),
@@ -164,7 +165,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 string.Empty,
                 new ActionContext() { HttpContext = new DefaultHttpContext() },
                 metadataProvider,
-                GetCompositeBinder(binder),
+                GetModelBinderFactory(binder),
                 Mock.Of<IValueProvider>(),
                 new List<IInputFormatter>(),
                 new Mock<IObjectModelValidator>(MockBehavior.Strict).Object,
@@ -182,10 +183,10 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         public async Task TryUpdateModel_UsingIncludePredicateOverload_ReturnsTrue_ModelBindsAndValidatesSuccessfully()
         {
             // Arrange
-            var binders = new IModelBinder[]
+            var binderProviders = new IModelBinderProvider[]
             {
-                new SimpleTypeModelBinder(),
+                new SimpleTypeModelBinderProvider(),
-                new MutableObjectModelBinder()
+                new ComplexTypeModelBinderProvider(),
             };
 
             var validator = new DataAnnotationsModelValidatorProvider(
@@ -220,7 +221,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 "",
                 new ActionContext() { HttpContext = new DefaultHttpContext() },
                 metadataProvider,
-                GetCompositeBinder(binders),
+                GetModelBinderFactory(binderProviders),
                 valueProvider,
                 new List<IInputFormatter>(),
                 new DefaultObjectValidator(metadataProvider, new ValidatorCache()),
@@ -250,7 +251,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 string.Empty,
                 new ActionContext() { HttpContext = new DefaultHttpContext() },
                 metadataProvider,
-                GetCompositeBinder(binder),
+                GetModelBinderFactory(binder),
                 Mock.Of<IValueProvider>(),
                 new List<IInputFormatter>(),
                 new Mock<IObjectModelValidator>(MockBehavior.Strict).Object,
@@ -268,10 +269,10 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         public async Task TryUpdateModel_UsingIncludeExpressionOverload_ReturnsTrue_ModelBindsAndValidatesSuccessfully()
         {
             // Arrange
-            var binders = new IModelBinder[]
+            var binderProviders = new IModelBinderProvider[]
             {
-                new SimpleTypeModelBinder(),
+                new SimpleTypeModelBinderProvider(),
-                new MutableObjectModelBinder()
+                new ComplexTypeModelBinderProvider(),
             };
 
             var validator = new DataAnnotationsModelValidatorProvider(
@@ -302,7 +303,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 "",
                 new ActionContext() { HttpContext = new DefaultHttpContext() },
                 TestModelMetadataProvider.CreateDefaultProvider(),
-                GetCompositeBinder(binders),
+                GetModelBinderFactory(binderProviders),
                 valueProvider,
                 new List<IInputFormatter>(),
                 new DefaultObjectValidator(metadataProvider, new ValidatorCache()),
@@ -321,10 +322,10 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         public async Task TryUpdateModel_UsingDefaultIncludeOverload_IncludesAllProperties()
         {
             // Arrange
-            var binders = new IModelBinder[]
+            var binderProviders = new IModelBinderProvider[]
             {
-                new SimpleTypeModelBinder(),
+                new SimpleTypeModelBinderProvider(),
-                new MutableObjectModelBinder()
+                new ComplexTypeModelBinderProvider(),
             };
 
             var validator = new DataAnnotationsModelValidatorProvider(
@@ -355,7 +356,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 "",
                 new ActionContext() { HttpContext = new DefaultHttpContext() },
                 metadataProvider,
-                GetCompositeBinder(binders),
+                GetModelBinderFactory(binderProviders),
                 valueProvider,
                 new List<IInputFormatter>(),
                 new DefaultObjectValidator(metadataProvider, new ValidatorCache()),
@@ -506,7 +507,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 prefix: "",
                 actionContext: new ActionContext() { HttpContext = new DefaultHttpContext() },
                 metadataProvider: metadataProvider,
-                modelBinder: GetCompositeBinder(binder),
+                modelBinderFactory: GetModelBinderFactory(binder),
                 valueProvider: Mock.Of<IValueProvider>(),
                 inputFormatters: new List<IInputFormatter>(),
                 objectModelValidator: new Mock<IObjectModelValidator>(MockBehavior.Strict).Object,
@@ -524,10 +525,10 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         public async Task TryUpdateModelNonGeneric_PredicateOverload_ReturnsTrue_ModelBindsAndValidatesSuccessfully()
         {
             // Arrange
-            var binders = new IModelBinder[]
+            var binderProviders = new IModelBinderProvider[]
             {
-                new SimpleTypeModelBinder(),
+                new SimpleTypeModelBinderProvider(),
-                new MutableObjectModelBinder()
+                new ComplexTypeModelBinderProvider(),
             };
 
             var validator = new DataAnnotationsModelValidatorProvider(
@@ -563,7 +564,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 "",
                 new ActionContext() { HttpContext = new DefaultHttpContext() },
                 metadataProvider,
-                GetCompositeBinder(binders),
+                GetModelBinderFactory(binderProviders),
                 valueProvider,
                 new List<IInputFormatter>(),
                 new DefaultObjectValidator(metadataProvider, new ValidatorCache()),
@@ -595,7 +596,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 prefix: "",
                 actionContext: new ActionContext() { HttpContext = new DefaultHttpContext() },
                 metadataProvider: metadataProvider,
-                modelBinder: GetCompositeBinder(binder.Object),
+                modelBinderFactory: GetModelBinderFactory(binder.Object),
                 valueProvider: Mock.Of<IValueProvider>(),
                 inputFormatters: new List<IInputFormatter>(),
                 objectModelValidator: new Mock<IObjectModelValidator>(MockBehavior.Strict).Object,
@@ -610,10 +611,10 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
         public async Task TryUpdateModelNonGeneric_ModelTypeOverload_ReturnsTrue_IfModelBindsAndValidatesSuccessfully()
         {
             // Arrange
-            var binders = new IModelBinder[]
+            var binderProviders = new IModelBinderProvider[]
             {
-                new SimpleTypeModelBinder(),
+                new SimpleTypeModelBinderProvider(),
-                new MutableObjectModelBinder()
+                new ComplexTypeModelBinderProvider(),
             };
 
             var validator = new DataAnnotationsModelValidatorProvider(
@@ -637,7 +638,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 "",
                 new ActionContext() { HttpContext = new DefaultHttpContext() },
                 TestModelMetadataProvider.CreateDefaultProvider(),
-                GetCompositeBinder(binders),
+                GetModelBinderFactory(binderProviders),
                 valueProvider,
                 new List<IInputFormatter>(),
                 new DefaultObjectValidator(metadataProvider, new ValidatorCache()),
@@ -666,7 +667,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                     "",
                     new ActionContext() { HttpContext = new DefaultHttpContext() },
                     metadataProvider,
-                    GetCompositeBinder(binder.Object),
+                    GetModelBinderFactory(binder.Object),
                     Mock.Of<IValueProvider>(),
                     new List<IInputFormatter>(),
                     new DefaultObjectValidator(metadataProvider, new ValidatorCache()),
@@ -816,9 +817,19 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             }
         }
 
-        private static IModelBinder GetCompositeBinder(params IModelBinder[] binders)
+        public static ModelBinderFactory GetModelBinderFactory(IModelBinder binder)
         {
-            return new CompositeModelBinder(binders);
+            var binderProvider = new Mock<IModelBinderProvider>();
+            binderProvider
+                .Setup(p => p.GetBinder(It.IsAny<ModelBinderProviderContext>()))
+                .Returns(binder);
+
+            return TestModelBinderFactory.Create(binderProvider.Object);
+        }
+
+        private static ModelBinderFactory GetModelBinderFactory(params IModelBinderProvider[] providers)
+        {
+            return TestModelBinderFactory.CreateDefault(providers);
         }
 
         public class User

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/SimpleValueProvider.cs

@@ -5,7 +5,7 @@ using System;
 using System.Collections.Generic;
 using System.Globalization;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
+namespace Microsoft.AspNetCore.Mvc.ModelBinding
 {
     public sealed class SimpleValueProvider : Dictionary<string, object>, IValueProvider
     {

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/StubModelBinder.cs

@@ -6,7 +6,7 @@ using System.Diagnostics;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Mvc.Internal;
 
-namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
+namespace Microsoft.AspNetCore.Mvc.ModelBinding
 {
     public class StubModelBinder : IModelBinder
     {

test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/TestModelBinderProviderContext.cs

@@ -0,0 +1,69 @@
+// 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;
+using System.Collections.Generic;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding
+{
+    public class TestModelBinderProviderContext : ModelBinderProviderContext
+    {
+        // Has to be internal because TestModelMetadataProvider is 'shared' code.
+        internal static readonly TestModelMetadataProvider CachedMetadataProvider = new TestModelMetadataProvider();
+
+        private readonly List<Func<ModelMetadata, IModelBinder>> _binderCreators = 
+            new List<Func<ModelMetadata, IModelBinder>>();
+
+        public TestModelBinderProviderContext(Type modelType)
+        {
+            Metadata = CachedMetadataProvider.GetMetadataForType(modelType);
+            MetadataProvider = CachedMetadataProvider;
+            BindingInfo = new BindingInfo()
+            {
+                BinderModelName = Metadata.BinderModelName,
+                BinderType = Metadata.BinderType,
+                BindingSource = Metadata.BindingSource,
+                PropertyBindingPredicateProvider = Metadata.PropertyBindingPredicateProvider,
+            };
+
+        }
+
+        public TestModelBinderProviderContext(ModelMetadata metadata, BindingInfo bindingInfo)
+        {
+            Metadata = metadata;
+            BindingInfo = bindingInfo;
+
+            MetadataProvider = CachedMetadataProvider;
+        }
+
+        public override BindingInfo BindingInfo { get; }
+
+        public override ModelMetadata Metadata { get; }
+
+        public override IModelMetadataProvider MetadataProvider { get; }
+
+        public override IModelBinder CreateBinder(ModelMetadata metadata)
+        {
+            foreach (var creator in _binderCreators)
+            {
+                var result = creator(metadata);
+                if (result != null)
+                {
+                    return result;
+                }
+            }
+
+            return null;
+        }
+
+        public void OnCreatingBinder(Func<ModelMetadata, IModelBinder> binderCreator)
+        {
+            _binderCreators.Add(binderCreator);
+        }
+
+        public void OnCreatingBinder(ModelMetadata metadata, Func<IModelBinder> binderCreator)
+        {
+            _binderCreators.Add((m) => m.Equals(metadata) ? binderCreator() : null);
+        }
+    }
+}

test/Microsoft.AspNetCore.Mvc.IntegrationTests/BinderTypeBasedModelBinderIntegrationTest.cs

@@ -73,7 +73,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var modelBindingResult = await argumentBinder.BindModelAsync(parameter, operationContext);
 
             // Assert
-            Assert.Equal(null, modelBindingResult);
+            Assert.False(modelBindingResult.Value.IsModelSet);
 
             // ModelState (not set unless inner binder sets it)
             Assert.True(modelState.IsValid);
@@ -110,7 +110,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             // Assert
 
             // ModelBindingResult
-            Assert.Equal(null, modelBindingResult);
+            Assert.False(modelBindingResult.Value.IsModelSet);
 
             // ModelState
             Assert.True(modelState.IsValid);
@@ -146,7 +146,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             // Assert
 
             // ModelBindingResult
-            Assert.Equal(null, modelBindingResult);
+            Assert.False(modelBindingResult.Value.IsModelSet);
 
             // ModelState
             Assert.True(modelState.IsValid);

test/Microsoft.AspNetCore.Mvc.IntegrationTests/ByteArrayModelBinderIntegrationTest.cs

@@ -95,7 +95,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             // Assert
 
             // ModelBindingResult
-            Assert.Equal(default(ModelBindingResult), modelBindingResult);
+            Assert.False(modelBindingResult.IsModelSet);
 
             // ModelState
             Assert.True(modelState.IsValid);