Ensure IFormFile binding for nested properties works (#12847)

* Ensure IFormFile binding for nested properties works

Fixes https://github.com/aspnet/AspNetCore/issues/9510

src/Components/test/E2ETest/ServerExecutionTests/InteropReliabilityTests.cs

@@ -259,7 +259,7 @@ namespace Microsoft.AspNetCore.Components.E2ETest.ServerExecutionTests
             await ValidateClientKeepsWorking(Client, batches);
         }
 
-        [Fact]
+        [Fact(Skip = "https://github.com/aspnet/AspNetCore/issues/12962")]
         public async Task LogsJSInteropCompletionsCallbacksAndContinuesWorkingInAllSituations()
         {
             // Arrange

src/Mvc/Mvc.Core/ref/Microsoft.AspNetCore.Mvc.Core.netcoreapp3.0.cs

@@ -2560,6 +2560,17 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
     {
         public EmptyModelMetadataProvider() : base (default(Microsoft.AspNetCore.Mvc.ModelBinding.Metadata.ICompositeMetadataDetailsProvider)) { }
     }
+    public sealed partial class FormFileValueProvider : Microsoft.AspNetCore.Mvc.ModelBinding.IValueProvider
+    {
+        public FormFileValueProvider(Microsoft.AspNetCore.Http.IFormFileCollection files) { }
+        public bool ContainsPrefix(string prefix) { throw null; }
+        public Microsoft.AspNetCore.Mvc.ModelBinding.ValueProviderResult GetValue(string key) { throw null; }
+    }
+    public sealed partial class FormFileValueProviderFactory : Microsoft.AspNetCore.Mvc.ModelBinding.IValueProviderFactory
+    {
+        public FormFileValueProviderFactory() { }
+        public System.Threading.Tasks.Task CreateValueProviderAsync(Microsoft.AspNetCore.Mvc.ModelBinding.ValueProviderFactoryContext context) { throw null; }
+    }
     public partial class FormValueProvider : Microsoft.AspNetCore.Mvc.ModelBinding.BindingSourceValueProvider, Microsoft.AspNetCore.Mvc.ModelBinding.IEnumerableValueProvider, Microsoft.AspNetCore.Mvc.ModelBinding.IValueProvider
     {
         public FormValueProvider(Microsoft.AspNetCore.Mvc.ModelBinding.BindingSource bindingSource, Microsoft.AspNetCore.Http.IFormCollection values, System.Globalization.CultureInfo culture) : base (default(Microsoft.AspNetCore.Mvc.ModelBinding.BindingSource)) { }

src/Mvc/Mvc.Core/src/Infrastructure/MvcCoreMvcOptionsSetup.cs

@@ -96,6 +96,7 @@ namespace Microsoft.AspNetCore.Mvc
             options.ValueProviderFactories.Add(new RouteValueProviderFactory());
             options.ValueProviderFactories.Add(new QueryStringValueProviderFactory());
             options.ValueProviderFactories.Add(new JQueryFormValueProviderFactory());
+            options.ValueProviderFactories.Add(new FormFileValueProviderFactory());
 
             // Set up metadata providers
             ConfigureAdditionalModelMetadataDetailsProviders(options.ModelMetadataDetailsProviders);

src/Mvc/Mvc.Core/src/ModelBinding/FormFileValueProvider.cs

@@ -0,0 +1,68 @@
+// 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;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding
+{
+    /// <summary>
+    /// An <see cref="IValueProvider"/> adapter for data stored in an <see cref="IFormFileCollection"/>.
+    /// </summary>
+    /// <remarks>
+    /// Unlike most <see cref="IValueProvider"/> instances, <see cref="FormFileValueProvider"/> does not provide any values, but
+    /// specifically responds to <see cref="ContainsPrefix(string)"/> queries. This allows the model binding system to
+    /// recurse in to deeply nested object graphs with only values for form files.
+    /// </remarks>
+    public sealed class FormFileValueProvider : IValueProvider
+    {
+        private readonly IFormFileCollection _files;
+        private PrefixContainer _prefixContainer;
+
+        /// <summary>
+        /// Creates a value provider for <see cref="IFormFileCollection"/>.
+        /// </summary>
+        /// <param name="files">The <see cref="IFormFileCollection"/>.</param>
+        public FormFileValueProvider(IFormFileCollection files)
+        {
+            _files = files ?? throw new ArgumentNullException(nameof(files));
+        }
+
+        private PrefixContainer PrefixContainer
+        {
+            get
+            {
+                _prefixContainer ??= CreatePrefixContainer(_files);
+                return _prefixContainer;
+            }
+        }
+
+        private static PrefixContainer CreatePrefixContainer(IFormFileCollection formFiles)
+        {
+            var fileNames = new List<string>();
+            var count = formFiles.Count;
+            for (var i = 0; i < count; i++)
+            {
+                var file = formFiles[i];
+
+                // If there is an <input type="file" ... /> in the form and is left blank.
+                // This matches the filtering behavior from FormFileModelBinder
+                if (file.Length == 0 && string.IsNullOrEmpty(file.FileName))
+                {
+                    continue;
+                }
+
+                fileNames.Add(file.Name);
+            }
+
+            return new PrefixContainer(fileNames);
+        }
+
+        /// <inheritdoc />
+        public bool ContainsPrefix(string prefix) => PrefixContainer.ContainsPrefix(prefix);
+
+        /// <inheritdoc />
+        public ValueProviderResult GetValue(string key) => ValueProviderResult.None;
+    }
+}

src/Mvc/Mvc.Core/src/ModelBinding/FormFileValueProviderFactory.cs

@@ -0,0 +1,43 @@
+// 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 Microsoft.AspNetCore.Http;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding
+{
+    /// <summary>
+    /// A <see cref="IValueProviderFactory"/> for <see cref="FormValueProvider"/>.
+    /// </summary>
+    public sealed class FormFileValueProviderFactory : IValueProviderFactory
+    {
+        /// <inheritdoc />
+        public Task CreateValueProviderAsync(ValueProviderFactoryContext context)
+        {
+            if (context == null)
+            {
+                throw new ArgumentNullException(nameof(context));
+            }
+
+            var request = context.ActionContext.HttpContext.Request;
+            if (request.HasFormContentType)
+            {
+                // Allocating a Task only when the body is multipart form.
+                return AddValueProviderAsync(context, request);
+            }
+
+            return Task.CompletedTask;
+        }
+
+        private static async Task AddValueProviderAsync(ValueProviderFactoryContext context, HttpRequest request)
+        {
+            var formCollection = await request.ReadFormAsync();
+            if (formCollection.Files.Count > 0)
+            {
+                var valueProvider = new FormFileValueProvider(formCollection.Files);
+                context.ValueProviders.Add(valueProvider);
+            }
+        }
+    }
+}

src/Mvc/Mvc.Core/test/Microsoft.AspNetCore.Mvc.Core.Test.csproj

@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>netcoreapp3.0</TargetFramework>
+    <RootNamespace>Microsoft.AspNetCore.Mvc</RootNamespace>
   </PropertyGroup>
 
   <ItemGroup>

src/Mvc/Mvc.Core/test/ModelBinding/FormFileValueProviderFactoryTest.cs

@@ -0,0 +1,73 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Collections.Generic;
+using System.IO;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Mvc.Abstractions;
+using Microsoft.AspNetCore.Routing;
+using Microsoft.Extensions.Primitives;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding
+{
+    public class FormFileValueProviderFactoryTest
+    {
+        [Fact]
+        public async Task CreateValueProviderAsync_DoesNotAddValueProvider_IfRequestDoesNotHaveFormContent()
+        {
+            // Arrange
+            var factory = new FormFileValueProviderFactory();
+            var context = CreateContext("application/json");
+
+            // Act
+            await factory.CreateValueProviderAsync(context);
+
+            // Assert
+            Assert.Empty(context.ValueProviders);
+        }
+
+        [Fact]
+        public async Task CreateValueProviderAsync_DoesNotAddValueProvider_IfFileCollectionIsEmpty()
+        {
+            // Arrange
+            var factory = new FormFileValueProviderFactory();
+            var context = CreateContext("multipart/form-data");
+
+            // Act
+            await factory.CreateValueProviderAsync(context);
+
+            // Assert
+            Assert.Empty(context.ValueProviders);
+        }
+
+        [Fact]
+        public async Task CreateValueProviderAsync_AddsValueProvider()
+        {
+            // Arrange
+            var factory = new FormFileValueProviderFactory();
+            var context = CreateContext("multipart/form-data; boundary=----WebKitFormBoundarymx2fSWqWSd0OxQqq");
+            var files = (FormFileCollection)context.ActionContext.HttpContext.Request.Form.Files;
+            files.Add(new FormFile(Stream.Null, 0, 10, "some-name", "some-name"));
+
+            // Act
+            await factory.CreateValueProviderAsync(context);
+
+            // Assert
+            Assert.Collection(
+                context.ValueProviders,
+                v => Assert.IsType<FormFileValueProvider>(v));
+        }
+
+        private static ValueProviderFactoryContext CreateContext(string contentType)
+        {
+            var context = new DefaultHttpContext();
+            context.Request.ContentType = contentType;
+            context.Request.Form = new FormCollection(new Dictionary<string, StringValues>(), new FormFileCollection());
+            var actionContext = new ActionContext(context, new RouteData(), new ActionDescriptor());
+
+            return new ValueProviderFactoryContext(actionContext);
+        }
+    }
+}

src/Mvc/Mvc.Core/test/ModelBinding/FormFileValueProviderTest.cs

@@ -0,0 +1,71 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Collections.Generic;
+using System.IO;
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.Primitives;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Mvc.ModelBinding
+{
+    public class FormFileValueProviderTest
+    {
+        [Fact]
+        public void ContainsPrefix_ReturnsFalse_IfFileIs0LengthAndFileNameIsEmpty()
+        {
+            // Arrange
+            var httpContext = new DefaultHttpContext();
+            httpContext.Request.ContentType = "multipart/form-data";
+            var formFiles = new FormFileCollection();
+            formFiles.Add(new FormFile(Stream.Null, 0, 0, "file", fileName: null));
+            httpContext.Request.Form = new FormCollection(new Dictionary<string, StringValues>(), formFiles);
+
+            var valueProvider = new FormFileValueProvider(formFiles);
+
+            // Act
+            var result = valueProvider.ContainsPrefix("file");
+
+            // Assert
+            Assert.False(result);
+        }
+
+        [Fact]
+        public void ContainsPrefix_ReturnsTrue_IfFileExists()
+        {
+            // Arrange
+            var httpContext = new DefaultHttpContext();
+            httpContext.Request.ContentType = "multipart/form-data";
+            var formFiles = new FormFileCollection();
+            formFiles.Add(new FormFile(Stream.Null, 0, 10, "file", "file"));
+            httpContext.Request.Form = new FormCollection(new Dictionary<string, StringValues>(), formFiles);
+
+            var valueProvider = new FormFileValueProvider(formFiles);
+
+            // Act
+            var result = valueProvider.ContainsPrefix("file");
+
+            // Assert
+            Assert.True(result);
+        }
+
+        [Fact]
+        public void GetValue_ReturnsNoneResult()
+        {
+            // Arrange
+            var httpContext = new DefaultHttpContext();
+            httpContext.Request.ContentType = "multipart/form-data";
+            var formFiles = new FormFileCollection();
+            formFiles.Add(new FormFile(Stream.Null, 0, 10, "file", "file"));
+            httpContext.Request.Form = new FormCollection(new Dictionary<string, StringValues>(), formFiles);
+
+            var valueProvider = new FormFileValueProvider(formFiles);
+
+            // Act
+            var result = valueProvider.GetValue("file");
+
+            // Assert
+            Assert.Equal(ValueProviderResult.None, result);
+        }
+    }
+}

src/Mvc/Mvc.ViewFeatures/src/Rendering/SystemTextJsonHelper.cs

@@ -1,5 +1,4 @@
-
+// Copyright (c) .NET Foundation. All rights reserved.
-// 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.Text.Encodings.Web;

src/Mvc/Mvc/test/MvcOptionsSetupTest.cs

@@ -82,7 +82,8 @@ namespace Microsoft.AspNetCore.Mvc
                 provider => Assert.IsType<FormValueProviderFactory>(provider),
                 provider => Assert.IsType<RouteValueProviderFactory>(provider),
                 provider => Assert.IsType<QueryStringValueProviderFactory>(provider),
-                provider => Assert.IsType<JQueryFormValueProviderFactory>(provider));
+                provider => Assert.IsType<JQueryFormValueProviderFactory>(provider),
+                provider => Assert.IsType<FormFileValueProviderFactory>(provider));
         }
 
         [Fact]

src/Mvc/test/Mvc.IntegrationTests/FormFileModelBindingIntegrationTest.cs

@@ -3,6 +3,7 @@
 
 using System.Collections.Generic;
 using System.IO;
+using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http;
@@ -75,6 +76,397 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.Equal(ModelValidationState.Valid, modelState[key].ValidationState);
         }
 
+        [Fact]
+        public async Task BindProperty_WithOnlyFormFile_WithEmptyPrefix()
+        {
+            // Arrange
+            var parameterBinder = ModelBindingTestHelper.GetParameterBinder();
+            var parameter = new ParameterDescriptor()
+            {
+                Name = "Parameter1",
+                BindingInfo = new BindingInfo(),
+                ParameterType = typeof(Person)
+            };
+
+            var data = "Some Data Is Better Than No Data.";
+            var testContext = ModelBindingTestHelper.GetTestContext(
+                request =>
+                {
+                    UpdateRequest(request, data, "Address.File");
+                });
+
+            var modelState = testContext.ModelState;
+
+            // Act
+            var modelBindingResult = await parameterBinder.BindModelAsync(parameter, testContext);
+
+            // Assert
+
+            // ModelBindingResult
+            Assert.True(modelBindingResult.IsModelSet);
+
+            // Model
+            var boundPerson = Assert.IsType<Person>(modelBindingResult.Model);
+            Assert.NotNull(boundPerson.Address);
+            var file = Assert.IsAssignableFrom<IFormFile>(boundPerson.Address.File);
+            Assert.Equal("form-data; name=Address.File; filename=text.txt", file.ContentDisposition);
+            using var reader = new StreamReader(boundPerson.Address.File.OpenReadStream());
+            Assert.Equal(data, reader.ReadToEnd());
+
+            // ModelState
+            Assert.True(modelState.IsValid);
+            Assert.Collection(
+                modelState.OrderBy(kvp => kvp.Key),
+                kvp =>
+                {
+                    var (key, value) = kvp;
+                    Assert.Equal("Address.File", kvp.Key);
+                    Assert.Null(value.RawValue);
+                    Assert.Empty(value.Errors);
+                    Assert.Equal(ModelValidationState.Valid, value.ValidationState);
+                });
+        }
+
+        [Fact]
+        public async Task BindProperty_WithOnlyFormFile_WithPrefix()
+        {
+            // Arrange
+            var parameterBinder = ModelBindingTestHelper.GetParameterBinder();
+            var parameter = new ParameterDescriptor()
+            {
+                Name = "Parameter1",
+                BindingInfo = new BindingInfo(),
+                ParameterType = typeof(Person)
+            };
+
+            var data = "Some Data Is Better Than No Data.";
+            var testContext = ModelBindingTestHelper.GetTestContext(
+                request =>
+                {
+                    UpdateRequest(request, data, "Parameter1.Address.File");
+                });
+
+            var modelState = testContext.ModelState;
+
+            // Act
+            var modelBindingResult = await parameterBinder.BindModelAsync(parameter, testContext);
+
+            // Assert
+
+            // ModelBindingResult
+            Assert.True(modelBindingResult.IsModelSet);
+
+            // Model
+            var boundPerson = Assert.IsType<Person>(modelBindingResult.Model);
+            Assert.NotNull(boundPerson.Address);
+            var file = Assert.IsAssignableFrom<IFormFile>(boundPerson.Address.File);
+            Assert.Equal("form-data; name=Parameter1.Address.File; filename=text.txt", file.ContentDisposition);
+            using var reader = new StreamReader(boundPerson.Address.File.OpenReadStream());
+            Assert.Equal(data, reader.ReadToEnd());
+
+            // ModelState
+            Assert.True(modelState.IsValid);
+            Assert.Collection(
+                modelState.OrderBy(kvp => kvp.Key),
+                kvp =>
+                {
+                    var (key, value) = kvp;
+                    Assert.Equal("Parameter1.Address.File", kvp.Key);
+                    Assert.Null(value.RawValue);
+                    Assert.Empty(value.Errors);
+                    Assert.Equal(ModelValidationState.Valid, value.ValidationState);
+                });
+        }
+
+        private class Group
+        {
+            public string GroupName { get; set; }
+
+            public Person Person { get; set; }
+        }
+
+        [Fact]
+        public async Task BindProperty_OnFormFileInNestedSubClass_AtSecondLevel_WhenSiblingPropertyIsSpecified()
+        {
+            // Arrange
+            var parameterBinder = ModelBindingTestHelper.GetParameterBinder();
+            var parameter = new ParameterDescriptor()
+            {
+                Name = "Parameter1",
+                BindingInfo = new BindingInfo(),
+                ParameterType = typeof(Group)
+            };
+
+            var data = "Some Data Is Better Than No Data.";
+            var testContext = ModelBindingTestHelper.GetTestContext(
+                request =>
+                {
+                    request.QueryString = QueryString.Create("Person.Address.Zip", "98056");
+                    UpdateRequest(request, data, "Person.Address.File");
+                });
+
+            var modelState = testContext.ModelState;
+
+            // Act
+            var modelBindingResult = await parameterBinder.BindModelAsync(parameter, testContext);
+
+            // Assert
+
+            // ModelBindingResult
+            Assert.True(modelBindingResult.IsModelSet);
+
+            // Model
+            var group = Assert.IsType<Group>(modelBindingResult.Model);
+            Assert.Null(group.GroupName);
+            var boundPerson = group.Person;
+            Assert.NotNull(boundPerson);
+            Assert.NotNull(boundPerson.Address);
+            var file = Assert.IsAssignableFrom<IFormFile>(boundPerson.Address.File);
+            Assert.Equal("form-data; name=Person.Address.File; filename=text.txt", file.ContentDisposition);
+            using var reader = new StreamReader(boundPerson.Address.File.OpenReadStream());
+            Assert.Equal(data, reader.ReadToEnd());
+            Assert.Equal(98056, boundPerson.Address.Zip);
+
+            // ModelState
+            Assert.True(modelState.IsValid);
+            Assert.Collection(
+                modelState.OrderBy(kvp => kvp.Key),
+                kvp =>
+                {
+                    var (key, value) = kvp;
+                    Assert.Equal("Person.Address.File", kvp.Key);
+                    Assert.Null(value.RawValue);
+                    Assert.Empty(value.Errors);
+                    Assert.Equal(ModelValidationState.Valid, value.ValidationState);
+                },
+                kvp =>
+                {
+                    var (key, value) = kvp;
+                    Assert.Equal("Person.Address.Zip", kvp.Key);
+                    Assert.Equal("98056", value.RawValue);
+                    Assert.Empty(value.Errors);
+                    Assert.Equal(ModelValidationState.Valid, value.ValidationState);
+                });
+        }
+
+        private class Fleet
+        {
+            public int? Id { get; set; }
+
+            public FleetGarage Garage { get; set; }
+        }
+
+        public class FleetGarage
+        {
+            public string Name { get; set; }
+
+            public FleetVehicle[] Vehicles { get; set; }
+        }
+
+        public class FleetVehicle
+        {
+            public string Name { get; set; }
+
+            public IFormFile Spec { get; set; }
+
+            public FleetVehicle BackupVehicle { get; set; }
+        }
+
+        [Fact]
+        public async Task BindProperty_OnFormFileInNestedSubClass_AtSecondLevel_RecursiveModel()
+        {
+            // Arrange
+            var parameterBinder = ModelBindingTestHelper.GetParameterBinder();
+            var parameter = new ParameterDescriptor()
+            {
+                Name = "fleet",
+                BindingInfo = new BindingInfo(),
+                ParameterType = typeof(Fleet)
+            };
+
+            var data = "Some Data Is Better Than No Data.";
+            var testContext = ModelBindingTestHelper.GetTestContext(
+                request =>
+                {
+                    request.QueryString = QueryString.Create("fleet.Garage.Name", "WestEnd");
+                    UpdateRequest(request, data, "fleet.Garage.Vehicles[0].Spec");
+                });
+
+            var modelState = testContext.ModelState;
+
+            // Act
+            var modelBindingResult = await parameterBinder.BindModelAsync(parameter, testContext);
+
+            // Assert
+
+            // ModelBindingResult
+            Assert.True(modelBindingResult.IsModelSet);
+
+            // Model
+            var fleet = Assert.IsType<Fleet>(modelBindingResult.Model);
+            Assert.Null(fleet.Id);
+
+            Assert.NotNull(fleet.Garage);
+            Assert.NotNull(fleet.Garage.Vehicles);
+
+            var vehicle = Assert.Single(fleet.Garage.Vehicles);
+            var file = Assert.IsAssignableFrom<IFormFile>(vehicle.Spec);
+
+            using var reader = new StreamReader(file.OpenReadStream());
+            Assert.Equal(data, reader.ReadToEnd());
+            Assert.Null(vehicle.Name);
+            Assert.Null(vehicle.BackupVehicle);
+
+            // ModelState
+            Assert.True(modelState.IsValid);
+            Assert.Collection(
+                modelState.OrderBy(kvp => kvp.Key),
+                kvp =>
+                {
+                    var (key, value) = kvp;
+                    Assert.Equal("fleet.Garage.Name", kvp.Key);
+                    Assert.Equal("WestEnd", value.RawValue);
+                    Assert.Empty(value.Errors);
+                    Assert.Equal(ModelValidationState.Valid, value.ValidationState);
+                },
+                kvp =>
+                {
+                    var (key, value) = kvp;
+                    Assert.Equal("fleet.Garage.Vehicles[0].Spec", kvp.Key);
+                    Assert.Equal(ModelValidationState.Valid, value.ValidationState);
+                });
+        }
+
+        [Fact]
+        public async Task BindProperty_OnFormFileInNestedSubClass_AtThirdLevel_RecursiveModel()
+        {
+            // Arrange
+            var parameterBinder = ModelBindingTestHelper.GetParameterBinder();
+            var parameter = new ParameterDescriptor()
+            {
+                Name = "fleet",
+                BindingInfo = new BindingInfo(),
+                ParameterType = typeof(Fleet)
+            };
+
+            var data = "Some Data Is Better Than No Data.";
+            var testContext = ModelBindingTestHelper.GetTestContext(
+                request =>
+                {
+                    request.QueryString = QueryString.Create("fleet.Garage.Name", "WestEnd");
+                    UpdateRequest(request, data, "fleet.Garage.Vehicles[0].BackupVehicle.Spec");
+                });
+
+            var modelState = testContext.ModelState;
+
+            // Act
+            var modelBindingResult = await parameterBinder.BindModelAsync(parameter, testContext);
+
+            // Assert
+
+            // ModelBindingResult
+            Assert.True(modelBindingResult.IsModelSet);
+
+            // Model
+            var fleet = Assert.IsType<Fleet>(modelBindingResult.Model);
+            Assert.Null(fleet.Id);
+
+            Assert.NotNull(fleet.Garage);
+            Assert.NotNull(fleet.Garage.Vehicles);
+
+            var vehicle = Assert.Single(fleet.Garage.Vehicles);
+            Assert.Null(vehicle.Spec);
+            Assert.NotNull(vehicle.BackupVehicle);
+            var file = Assert.IsAssignableFrom<IFormFile>(vehicle.BackupVehicle.Spec);
+
+            using var reader = new StreamReader(file.OpenReadStream());
+            Assert.Equal(data, reader.ReadToEnd());
+            Assert.Null(vehicle.Name);
+
+            // ModelState
+            Assert.True(modelState.IsValid);
+            Assert.Collection(
+                modelState.OrderBy(kvp => kvp.Key),
+                kvp =>
+                {
+                    var (key, value) = kvp;
+                    Assert.Equal("fleet.Garage.Name", kvp.Key);
+                    Assert.Equal("WestEnd", value.RawValue);
+                    Assert.Empty(value.Errors);
+                    Assert.Equal(ModelValidationState.Valid, value.ValidationState);
+                },
+                kvp =>
+                {
+                    var (key, value) = kvp;
+                    Assert.Equal("fleet.Garage.Vehicles[0].BackupVehicle.Spec", kvp.Key);
+                    Assert.Equal(ModelValidationState.Valid, value.ValidationState);
+                });
+        }
+
+        [Fact]
+        public async Task BindProperty_OnFormFileInNestedSubClass_AtSecondLevel_WhenSiblingPropertiesAreNotSpecified()
+        {
+            // Arrange
+            var parameterBinder = ModelBindingTestHelper.GetParameterBinder();
+            var parameter = new ParameterDescriptor()
+            {
+                Name = "Parameter1",
+                BindingInfo = new BindingInfo(),
+                ParameterType = typeof(Group)
+            };
+
+            var data = "Some Data Is Better Than No Data.";
+            var testContext = ModelBindingTestHelper.GetTestContext(
+                request =>
+                {
+                    request.QueryString = QueryString.Create("GroupName", "TestGroup");
+                    UpdateRequest(request, data, "Person.Address.File");
+                });
+
+            var modelState = testContext.ModelState;
+
+            // Act
+            var modelBindingResult = await parameterBinder.BindModelAsync(parameter, testContext);
+
+            // Assert
+
+            // ModelBindingResult
+            Assert.True(modelBindingResult.IsModelSet);
+
+            // Model
+            var group = Assert.IsType<Group>(modelBindingResult.Model);
+            Assert.Equal("TestGroup", group.GroupName);
+            var boundPerson = group.Person;
+            Assert.NotNull(boundPerson);
+            Assert.NotNull(boundPerson.Address);
+            var file = Assert.IsAssignableFrom<IFormFile>(boundPerson.Address.File);
+            Assert.Equal("form-data; name=Person.Address.File; filename=text.txt", file.ContentDisposition);
+            using var reader = new StreamReader(boundPerson.Address.File.OpenReadStream());
+            Assert.Equal(data, reader.ReadToEnd());
+            Assert.Equal(0, boundPerson.Address.Zip);
+
+            // ModelState
+            Assert.True(modelState.IsValid);
+            Assert.Collection(
+                modelState.OrderBy(kvp => kvp.Key),
+                kvp =>
+                {
+                    var (key, value) = kvp;
+                    Assert.Equal("GroupName", kvp.Key);
+                    Assert.Equal("TestGroup", value.RawValue);
+                    Assert.Empty(value.Errors);
+                    Assert.Equal(ModelValidationState.Valid, value.ValidationState);
+                },
+                kvp =>
+                {
+                    var (key, value) = kvp;
+                    Assert.Equal("Person.Address.File", kvp.Key);
+                    Assert.Null(value.RawValue);
+                    Assert.Empty(value.Errors);
+                    Assert.Equal(ModelValidationState.Valid, value.ValidationState);
+                });
+        }
+
         private class ListContainer1
         {
             [ModelBinder(Name = "files")]
@@ -354,15 +746,526 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.Single(modelState, e => e.Key == "p.Specs");
         }
 
+        private class House
+        {
+            public Garage Garage { get; set; }
+        }
+
+        private class Garage
+        {
+            public List<Car1> Cars { get; set; }
+        }
+
+        [Fact]
+        public async Task BindProperty_FormFileCollectionInCollection_WithPrefix()
+        {
+            // Arrange
+            var parameterBinder = ModelBindingTestHelper.GetParameterBinder();
+            var parameter = new ParameterDescriptor
+            {
+                Name = "house",
+                BindingInfo = new BindingInfo(),
+                ParameterType = typeof(House)
+            };
+
+            var data = "Some Data Is Better Than No Data.";
+            var testContext = ModelBindingTestHelper.GetTestContext(
+                request =>
+                {
+                    request.QueryString = QueryString.Create("house.Garage.Cars[0].Name", "Accord");
+                    UpdateRequest(request, data + 1, "house.Garage.Cars[0].Specs");
+                    AddFormFile(request, data + 2, "house.Garage.Cars[1].Specs");
+                });
+
+            var modelState = testContext.ModelState;
+
+            // Act
+            var modelBindingResult = await parameterBinder.BindModelAsync(parameter, testContext);
+
+            // Assert
+
+            // ModelBindingResult
+            Assert.True(modelBindingResult.IsModelSet);
+
+            // Model
+            var house = Assert.IsType<House>(modelBindingResult.Model);
+            Assert.NotNull(house.Garage);
+            Assert.NotNull(house.Garage.Cars);
+            Assert.Collection(
+                house.Garage.Cars,
+                car =>
+                {
+                    Assert.Equal("Accord", car.Name);
+
+                    var file = Assert.Single(car.Specs);
+                    using var reader = new StreamReader(file.OpenReadStream());
+                    Assert.Equal(data + 1, reader.ReadToEnd());
+                },
+                car =>
+                {
+                    Assert.Null(car.Name);
+
+                    var file = Assert.Single(car.Specs);
+                    using var reader = new StreamReader(file.OpenReadStream());
+                    Assert.Equal(data + 2, reader.ReadToEnd());
+                });
+
+            // ModelState
+            Assert.True(modelState.IsValid);
+            Assert.Equal(3, modelState.Count);
+
+            var entry = Assert.Single(modelState, e => e.Key == "house.Garage.Cars[0].Name").Value;
+            Assert.Equal("Accord", entry.AttemptedValue);
+            Assert.Equal("Accord", entry.RawValue);
+
+            Assert.Single(modelState, e => e.Key == "house.Garage.Cars[0].Specs");
+            Assert.Single(modelState, e => e.Key == "house.Garage.Cars[1].Specs");
+        }
+
+        [Fact]
+        public async Task BindProperty_FormFileCollectionInCollection_OnlyFiles()
+        {
+            // Arrange
+            var parameterBinder = ModelBindingTestHelper.GetParameterBinder();
+            var parameter = new ParameterDescriptor
+            {
+                Name = "house",
+                BindingInfo = new BindingInfo(),
+                ParameterType = typeof(House)
+            };
+
+            var data = "Some Data Is Better Than No Data.";
+            var testContext = ModelBindingTestHelper.GetTestContext(
+                request =>
+                {
+                    UpdateRequest(request, data + 1, "house.Garage.Cars[0].Specs");
+                    AddFormFile(request, data + 2, "house.Garage.Cars[1].Specs");
+                });
+
+            var modelState = testContext.ModelState;
+
+            // Act
+            var modelBindingResult = await parameterBinder.BindModelAsync(parameter, testContext);
+
+            // Assert
+
+            // ModelBindingResult
+            Assert.True(modelBindingResult.IsModelSet);
+
+            // Model
+            var house = Assert.IsType<House>(modelBindingResult.Model);
+            Assert.NotNull(house.Garage);
+            Assert.NotNull(house.Garage.Cars);
+            Assert.Collection(
+                house.Garage.Cars,
+                car =>
+                {
+                    Assert.Null(car.Name);
+
+                    var file = Assert.Single(car.Specs);
+                    using var reader = new StreamReader(file.OpenReadStream());
+                    Assert.Equal(data + 1, reader.ReadToEnd());
+                },
+                car =>
+                {
+                    Assert.Null(car.Name);
+
+                    var file = Assert.Single(car.Specs);
+                    using var reader = new StreamReader(file.OpenReadStream());
+                    Assert.Equal(data + 2, reader.ReadToEnd());
+                });
+
+            // ModelState
+            Assert.True(modelState.IsValid);
+            Assert.Equal(2, modelState.Count);
+
+            Assert.Single(modelState, e => e.Key == "house.Garage.Cars[0].Specs");
+            Assert.Single(modelState, e => e.Key == "house.Garage.Cars[1].Specs");
+        }
+
+        [Fact]
+        public async Task BindProperty_FormFileCollectionInCollection_OutOfOrderFile()
+        {
+            // Arrange
+            var parameterBinder = ModelBindingTestHelper.GetParameterBinder();
+            var parameter = new ParameterDescriptor
+            {
+                Name = "house",
+                BindingInfo = new BindingInfo(),
+                ParameterType = typeof(House)
+            };
+
+            var data = "Some Data Is Better Than No Data.";
+            var testContext = ModelBindingTestHelper.GetTestContext(
+                request =>
+                {
+                    UpdateRequest(request, data + 1, "house.Garage.Cars[800].Specs");
+                });
+
+            var modelState = testContext.ModelState;
+
+            // Act
+            var modelBindingResult = await parameterBinder.BindModelAsync(parameter, testContext);
+
+            // Assert
+
+            // ModelBindingResult
+            Assert.True(modelBindingResult.IsModelSet);
+
+            // Model
+            var house = Assert.IsType<House>(modelBindingResult.Model);
+            Assert.NotNull(house.Garage);
+            Assert.Empty(house.Garage.Cars);
+
+            // ModelState
+            Assert.True(modelState.IsValid);
+            Assert.Empty(modelState);
+        }
+
+        [Fact]
+        public async Task BindProperty_FormFileCollectionInCollection_MultipleFiles()
+        {
+            // Arrange
+            var parameterBinder = ModelBindingTestHelper.GetParameterBinder();
+            var parameter = new ParameterDescriptor
+            {
+                Name = "house",
+                BindingInfo = new BindingInfo(),
+                ParameterType = typeof(House)
+            };
+
+            var data = "Some Data Is Better Than No Data.";
+            var testContext = ModelBindingTestHelper.GetTestContext(
+                request =>
+                {
+                    UpdateRequest(request, data + 1, "house.Garage.Cars[0].Specs");
+                    AddFormFile(request, data + 2, "house.Garage.Cars[0].Specs");
+                });
+
+            var modelState = testContext.ModelState;
+
+            // Act
+            var modelBindingResult = await parameterBinder.BindModelAsync(parameter, testContext);
+
+            // Assert
+
+            // ModelBindingResult
+            Assert.True(modelBindingResult.IsModelSet);
+
+            // Model
+            var house = Assert.IsType<House>(modelBindingResult.Model);
+            Assert.NotNull(house.Garage);
+            Assert.NotNull(house.Garage.Cars);
+            Assert.Collection(
+                house.Garage.Cars,
+                car =>
+                {
+                    Assert.Null(car.Name);
+                    Assert.Collection(
+                        car.Specs,
+                        file =>
+                        {
+                            using var reader = new StreamReader(file.OpenReadStream());
+                            Assert.Equal(data + 1, reader.ReadToEnd());
+
+                        },
+                        file =>
+                        {
+                            using var reader = new StreamReader(file.OpenReadStream());
+                            Assert.Equal(data + 2, reader.ReadToEnd());
+
+                        });
+                });
+
+            // ModelState
+            Assert.True(modelState.IsValid);
+            var kvp = Assert.Single(modelState);
+
+            Assert.Equal("house.Garage.Cars[0].Specs", kvp.Key);
+        }
+
+        [Fact]
+        public async Task BindProperty_FormFile_AsAPropertyOnNestedColection()
+        {
+            // Arrange
+            var parameterBinder = ModelBindingTestHelper.GetParameterBinder();
+            var parameter = new ParameterDescriptor
+            {
+                Name = "p",
+                BindingInfo = new BindingInfo(),
+                ParameterType = typeof(Car1)
+            };
+
+            var data = "Some Data Is Better Than No Data.";
+            var testContext = ModelBindingTestHelper.GetTestContext(
+                request =>
+                {
+                    request.QueryString = QueryString.Create("p.Name", "Accord");
+                    UpdateRequest(request, data, "p.Specs");
+                });
+
+            var modelState = testContext.ModelState;
+
+            // Act
+            var modelBindingResult = await parameterBinder.BindModelAsync(parameter, testContext);
+
+            // Assert
+
+            // ModelBindingResult
+            Assert.True(modelBindingResult.IsModelSet);
+
+            // Model
+            var car = Assert.IsType<Car1>(modelBindingResult.Model);
+            Assert.NotNull(car.Specs);
+            var file = Assert.Single(car.Specs);
+            Assert.Equal("form-data; name=p.Specs; filename=text.txt", file.ContentDisposition);
+            var reader = new StreamReader(file.OpenReadStream());
+            Assert.Equal(data, reader.ReadToEnd());
+
+            // ModelState
+            Assert.True(modelState.IsValid);
+            Assert.Equal(2, modelState.Count);
+
+            var entry = Assert.Single(modelState, e => e.Key == "p.Name").Value;
+            Assert.Equal("Accord", entry.AttemptedValue);
+            Assert.Equal("Accord", entry.RawValue);
+
+            Assert.Single(modelState, e => e.Key == "p.Specs");
+        }
+
+        public class MultiDimensionalFormFileContainer
+        {
+            public IFormFile[][] FormFiles { get; set; }
+        }
+
+        [Fact]
+        public async Task BindModelAsync_MultiDimensionalFormFile_Works()
+        {
+            // Arrange
+            var parameterBinder = ModelBindingTestHelper.GetParameterBinder();
+            var parameter = new ParameterDescriptor
+            {
+                Name = "p",
+                BindingInfo = new BindingInfo(),
+                ParameterType = typeof(MultiDimensionalFormFileContainer)
+            };
+
+            var data = "Some Data Is Better Than No Data.";
+            var testContext = ModelBindingTestHelper.GetTestContext(
+                request =>
+                {
+                    UpdateRequest(request, data + 1, "FormFiles[0]");
+                    AddFormFile(request, data + 2, "FormFiles[1]");
+                    AddFormFile(request, data + 3, "FormFiles[1]");
+                });
+
+            var modelState = testContext.ModelState;
+
+            // Act
+            var modelBindingResult = await parameterBinder.BindModelAsync(parameter, testContext);
+
+            // Assert
+
+            // ModelBindingResult
+            Assert.True(modelBindingResult.IsModelSet);
+
+            // Model
+            var container = Assert.IsType<MultiDimensionalFormFileContainer>(modelBindingResult.Model);
+            Assert.NotNull(container.FormFiles);
+            Assert.Collection(
+                container.FormFiles,
+                item =>
+                {
+                    Assert.Collection(
+                        item,
+                        file => Assert.Equal(data + 1, ReadFormFile(file)));
+                },
+                item =>
+                {
+                    Assert.Collection(
+                        item,
+                        file => Assert.Equal(data + 2, ReadFormFile(file)),
+                        file => Assert.Equal(data + 3, ReadFormFile(file)));
+                });
+        }
+
+        [Fact]
+        public async Task BindModelAsync_MultiDimensionalFormFile_WithArrayNotation()
+        {
+            // Arrange
+            var parameterBinder = ModelBindingTestHelper.GetParameterBinder();
+            var parameter = new ParameterDescriptor
+            {
+                Name = "p",
+                BindingInfo = new BindingInfo(),
+                ParameterType = typeof(MultiDimensionalFormFileContainer)
+            };
+
+            var data = "Some Data Is Better Than No Data.";
+            var testContext = ModelBindingTestHelper.GetTestContext(
+                request =>
+                {
+                    UpdateRequest(request, data + 1, "FormFiles[0][0]");
+                    AddFormFile(request, data + 2, "FormFiles[1][0]");
+                    AddFormFile(request, data + 3, "FormFiles[1][0]");
+                });
+
+            var modelState = testContext.ModelState;
+
+            // Act
+            var modelBindingResult = await parameterBinder.BindModelAsync(parameter, testContext);
+
+            // Assert
+
+            // ModelBindingResult
+            Assert.True(modelBindingResult.IsModelSet);
+            var container = Assert.IsType<MultiDimensionalFormFileContainer>(modelBindingResult.Model);
+            Assert.NotNull(container.FormFiles);
+            Assert.Empty(container.FormFiles);
+        }
+
+        public class MultiDimensionalFormFileContainerLevel2
+        {
+            public MultiDimensionalFormFileContainerLevel1 Level1 { get; set; }
+        }
+
+        public class MultiDimensionalFormFileContainerLevel1
+        {
+            public MultiDimensionalFormFileContainer Container { get; set; }
+        }
+
+        [Fact]
+        public async Task BindModelAsync_DeeplyNestedMultiDimensionalFormFile_Works()
+        {
+            // Arrange
+            var parameterBinder = ModelBindingTestHelper.GetParameterBinder();
+            var parameter = new ParameterDescriptor
+            {
+                Name = "p",
+                BindingInfo = new BindingInfo(),
+                ParameterType = typeof(MultiDimensionalFormFileContainerLevel2)
+            };
+
+            var data = "Some Data Is Better Than No Data.";
+            var testContext = ModelBindingTestHelper.GetTestContext(
+                request =>
+                {
+                    UpdateRequest(request, data + 1, "p.Level1.Container.FormFiles[0]");
+                    AddFormFile(request, data + 2, "p.Level1.Container.FormFiles[1]");
+                    AddFormFile(request, data + 3, "p.Level1.Container.FormFiles[1]");
+                });
+
+            var modelState = testContext.ModelState;
+
+            // Act
+            var modelBindingResult = await parameterBinder.BindModelAsync(parameter, testContext);
+
+            // Assert
+
+            // ModelBindingResult
+            Assert.True(modelBindingResult.IsModelSet);
+
+            // Model
+            var level2 = Assert.IsType<MultiDimensionalFormFileContainerLevel2>(modelBindingResult.Model);
+            Assert.NotNull(level2.Level1);
+            var container = level2.Level1.Container;
+            Assert.NotNull(container);
+            Assert.NotNull(container.FormFiles);
+            Assert.Collection(
+                container.FormFiles,
+                item =>
+                {
+                    Assert.Collection(
+                        item,
+                        file => Assert.Equal(data + 1, ReadFormFile(file)));
+                },
+                item =>
+                {
+                    Assert.Collection(
+                        item,
+                        file => Assert.Equal(data + 2, ReadFormFile(file)),
+                        file => Assert.Equal(data + 3, ReadFormFile(file)));
+                });
+        }
+
+        public class DictionaryContainer
+        {
+            public Dictionary<string, IFormFile> Dictionary { get; set; }
+        }
+
+        [Fact]
+        public async Task BindModelAsync_DictionaryOfFormFiles()
+        {
+            // Arrange
+            var parameterBinder = ModelBindingTestHelper.GetParameterBinder();
+            var parameter = new ParameterDescriptor
+            {
+                Name = "p",
+                BindingInfo = new BindingInfo(),
+                ParameterType = typeof(DictionaryContainer)
+            };
+
+            var data = "Some Data Is Better Than No Data.";
+            var testContext = ModelBindingTestHelper.GetTestContext(
+                request =>
+                {
+                    request.QueryString = QueryString.Create(new Dictionary<string, string>
+                    {
+                        { "p.Dictionary[0].Key", "key0" },
+                        { "p.Dictionary[1].Key", "key1" },
+                        { "p.Dictionary[4000].Key", "key1" },
+                    });
+                    UpdateRequest(request, data + 1, "p.Dictionary[0].Value");
+                    AddFormFile(request, data + 2, "p.Dictionary[1].Value");
+                });
+
+            var modelState = testContext.ModelState;
+
+            // Act
+            var modelBindingResult = await parameterBinder.BindModelAsync(parameter, testContext);
+
+            // Assert
+
+            // ModelBindingResult
+            Assert.True(modelBindingResult.IsModelSet);
+
+            // Model
+            var container = Assert.IsType<DictionaryContainer>(modelBindingResult.Model);
+            Assert.NotNull(container.Dictionary);
+            Assert.Collection(
+                container.Dictionary.OrderBy(kvp => kvp.Key),
+                kvp =>
+                {
+                    Assert.Equal("key0", kvp.Key);
+                    Assert.Equal(data + 1, ReadFormFile(kvp.Value));
+                },
+                kvp =>
+                {
+                    Assert.Equal("key1", kvp.Key);
+                    Assert.Equal(data + 2, ReadFormFile(kvp.Value));
+                });
+        }
+
+        private static string ReadFormFile(IFormFile file)
+        {
+            using var reader = new StreamReader(file.OpenReadStream());
+            return reader.ReadToEnd();
+        }
+
         private void UpdateRequest(HttpRequest request, string data, string name)
         {
-            const string fileName = "text.txt";
+            var formCollection = new FormCollection(new Dictionary<string, StringValues>(), new FormFileCollection());
-            var fileCollection = new FormFileCollection();
-            var formCollection = new FormCollection(new Dictionary<string, StringValues>(), fileCollection);
-
             request.Form = formCollection;
+
             request.ContentType = "multipart/form-data; boundary=----WebKitFormBoundarymx2fSWqWSd0OxQqq";
 
+            AddFormFile(request, data, name);
+        }
+
+        private void AddFormFile(HttpRequest request, string data, string name)
+        {
+            const string fileName = "text.txt";
+
             if (string.IsNullOrEmpty(data) || string.IsNullOrEmpty(name))
             {
                 // Leave the submission empty.
@@ -371,6 +1274,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
 
             request.Headers["Content-Disposition"] = $"form-data; name={name}; filename={fileName}";
 
+            var fileCollection = (FormFileCollection)request.Form.Files;
             var memoryStream = new MemoryStream(Encoding.UTF8.GetBytes(data));
             fileCollection.Add(new FormFile(memoryStream, 0, data.Length, name, fileName)
             {
@@ -378,4 +1282,4 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             });
         }
     }
-}
+}