Fix binding & validating dictionaries of non-simple types in jQuery requests

- #7423
- retry failed inner bindings with alternate syntax in `ModelStateDictionary`
  - use property syntax if first attempt tried index syntax and visa versa
- instantiate `ShortFormDictionaryValidationStrategy` with full `ModelState` keys
  - can now provide exact `ModelState` keys that `ModelStateDictionary` used in inner bindings
- normalize model names without a leading period in `JQueryKeyValuePairNormalizer`

nits:
- take a few VS suggestions

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

@@ -17,14 +17,14 @@ namespace Microsoft.AspNetCore.Mvc.Internal
     /// <remarks>
     /// This implementation handles cases like:
     /// <example>
-    ///     Model: IDictionary&lt;string, Student&gt; 
+    ///     Model: IDictionary&lt;string, Student&gt;
     ///     Query String: ?students[Joey].Age=8&amp;students[Katherine].Age=9
-    /// 
+    ///
     ///     In this case, 'Joey' and 'Katherine' are the keys of the dictionary, used to bind two 'Student'
     ///     objects. The enumerator returned from this class will yield two 'Student' objects with corresponding
     ///     keys 'students[Joey]' and 'students[Katherine]'
     /// </example>
-    /// 
+    ///
     /// Using this key format, the enumerator enumerates model objects of type <typeparamref name="TValue"/>. The
     /// keys of the dictionary are not validated as they must be simple types.
     /// </remarks>
@@ -35,7 +35,9 @@ namespace Microsoft.AspNetCore.Mvc.Internal
         /// <summary>
         /// Creates a new <see cref="ShortFormDictionaryValidationStrategy{TKey, TValue}"/>.
         /// </summary>
-        /// <param name="keyMappings">The mapping from model prefix key to dictionary key.</param>
+        /// <param name="keyMappings">
+        /// The mapping from <see cref="ModelStateDictionary"/> key to dictionary key.
+        /// </param>
         /// <param name="valueMetadata">
         /// The <see cref="ModelMetadata"/> associated with <typeparamref name="TValue"/>.
         /// </param>
@@ -48,7 +50,7 @@ namespace Microsoft.AspNetCore.Mvc.Internal
         }
 
         /// <summary>
-        /// Gets the mapping from model prefix key to dictionary key.
+        /// Gets the mapping from <see cref="ModelStateDictionary"/> key to dictionary key.
         /// </summary>
         public IEnumerable<KeyValuePair<string, TKey>> KeyMappings { get; }
 
@@ -58,12 +60,12 @@ namespace Microsoft.AspNetCore.Mvc.Internal
             string key,
             object model)
         {
-            return new Enumerator(_valueMetadata, key, KeyMappings, (IDictionary<TKey, TValue>)model);
+            // key is not needed because KeyMappings maps from full ModelState keys to dictionary keys.
+            return new Enumerator(_valueMetadata, KeyMappings, (IDictionary<TKey, TValue>)model);
         }
 
         private class Enumerator : IEnumerator<ValidationEntry>
         {
-            private readonly string _key;
             private readonly ModelMetadata _metadata;
             private readonly IDictionary<TKey, TValue> _model;
             private readonly IEnumerator<KeyValuePair<string, TKey>> _keyMappingEnumerator;
@@ -72,14 +74,11 @@ namespace Microsoft.AspNetCore.Mvc.Internal
 
             public Enumerator(
                 ModelMetadata metadata,
-                string key,
                 IEnumerable<KeyValuePair<string, TKey>> keyMappings,
                 IDictionary<TKey, TValue> model)
             {
                 _metadata = metadata;
-                _key = key;
                 _model = model;
-
                 _keyMappingEnumerator = keyMappings.GetEnumerator();
             }
 
@@ -104,10 +103,7 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                     }
                 }
 
-                var key = ModelNames.CreateIndexModelName(_key, _keyMappingEnumerator.Current.Key);
-                var model = value;
-
-                _entry = new ValidationEntry(_metadata, key, model);
+                _entry = new ValidationEntry(_metadata, _keyMappingEnumerator.Current.Key, value);
 
                 return true;
             }

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

@@ -81,8 +81,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 
             Logger.NoKeyValueFormatForDictionaryModelBinder(bindingContext);
 
-            var enumerableValueProvider = bindingContext.ValueProvider as IEnumerableValueProvider;
-            if (enumerableValueProvider == null)
+            if (!(bindingContext.ValueProvider is IEnumerableValueProvider enumerableValueProvider))
             {
                 // No IEnumerableValueProvider available for the fallback approach. For example the user may have
                 // replaced the ValueProvider with something other than a CompositeValueProvider.
@@ -90,7 +89,8 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
             }
 
             // Attempt to bind dictionary from a set of prefix[key]=value entries. Get the short and long keys first.
-            var keys = enumerableValueProvider.GetKeysFromPrefix(bindingContext.ModelName);
+            var prefix = bindingContext.ModelName;
+            var keys = enumerableValueProvider.GetKeysFromPrefix(prefix);
             if (keys.Count == 0)
             {
                 // No entries with the expected keys.
@@ -117,10 +117,29 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
                     await _valueBinder.BindModelAsync(bindingContext);
 
                     var valueResult = bindingContext.Result;
+                    if (!valueResult.IsModelSet)
+                    {
+                        // Factories for IKeyRewriterValueProvider implementations are not all-or-nothing i.e.
+                        // "[key][propertyName]" may be rewritten as ".key.propertyName" or "[key].propertyName". Try
+                        // again in case this scope is binding a complex type and rewriting
+                        // landed on ".key.propertyName" or in case this scope is binding another collection and an
+                        // IKeyRewriterValueProvider implementation was first (hiding the original "[key][next key]").
+                        if (kvp.Value.EndsWith("]"))
+                        {
+                            bindingContext.ModelName = ModelNames.CreatePropertyModelName(prefix, kvp.Key);
+                        }
+                        else
+                        {
+                            bindingContext.ModelName = ModelNames.CreateIndexModelName(prefix, kvp.Key);
+                        }
+
+                        await _valueBinder.BindModelAsync(bindingContext);
+                        valueResult = bindingContext.Result;
+                    }
 
                     // Always add an entry to the dictionary but validate only if binding was successful.
                     model[convertedKey] = ModelBindingHelper.CastOrDefault<TValue>(valueResult.Model);
-                    keyMappings.Add(kvp.Key, convertedKey);
+                    keyMappings.Add(bindingContext.ModelName, convertedKey);
                 }
             }
 

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

@@ -86,7 +86,12 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
                 else
                 {
                     // Field name. Convert to dot notation.
-                    builder.Append('.');
+                    if (builder.Length != 0)
+                    {
+                        // Was x[field], not [field] or [][field].
+                        builder.Append('.');
+                    }
+
                     builder.Append(key, indexOpen + 1, indexClose - indexOpen - 1);
                 }
 

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

@@ -7,7 +7,6 @@ using Microsoft.AspNetCore.Mvc.ModelBinding;
 using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;
 using Xunit;
 
-
 namespace Microsoft.AspNetCore.Mvc.Internal
 {
     public class ShortFormDictionaryValidationStrategyTest
@@ -28,14 +27,14 @@ namespace Microsoft.AspNetCore.Mvc.Internal
             var valueMetadata = metadataProvider.GetMetadataForType(typeof(string));
             var strategy = new ShortFormDictionaryValidationStrategy<int, string>(new Dictionary<string, int>()
             {
-                { "2", 2 },
-                { "3", 3 },
-                { "5", 5 },
+                { "prefix[2]", 2 },
+                { "prefix[3]", 3 },
+                { "prefix[5]", 5 },
             },
             valueMetadata);
 
             // Act
-            var enumerator = strategy.GetChildren(metadata, "prefix", model);
+            var enumerator = strategy.GetChildren(metadata, "ignored prefix", model);
 
             // Assert
             Assert.Collection(
@@ -76,13 +75,13 @@ namespace Microsoft.AspNetCore.Mvc.Internal
             var valueMetadata = metadataProvider.GetMetadataForType(typeof(string));
             var strategy = new ShortFormDictionaryValidationStrategy<int, string>(new Dictionary<string, int>()
             {
-                { "2", 2 },
-                { "3", 3 },
+                { "prefix[2]", 2 },
+                { "prefix[3]", 3 },
             },
             valueMetadata);
 
             // Act
-            var enumerator = strategy.GetChildren(metadata, "prefix", model);
+            var enumerator = strategy.GetChildren(metadata, "ignored prefix", model);
 
             // Assert
             Assert.Collection(
@@ -116,14 +115,14 @@ namespace Microsoft.AspNetCore.Mvc.Internal
             var valueMetadata = metadataProvider.GetMetadataForType(typeof(string));
             var strategy = new ShortFormDictionaryValidationStrategy<int, string>(new Dictionary<string, int>()
             {
-                { "2", 2 },
-                { "3", 3 },
-                { "5", 5 },
+                { "prefix[2]", 2 },
+                { "prefix[3]", 3 },
+                { "prefix[5]", 5 },
             },
             valueMetadata);
 
             // Act
-            var enumerator = strategy.GetChildren(metadata, "prefix", model);
+            var enumerator = strategy.GetChildren(metadata, "ignored prefix", model);
 
             // Assert
             Assert.Collection(

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

@@ -302,8 +302,8 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
             Assert.Equal(
                 new KeyValuePair<string, int>[]
                 {
-                    new KeyValuePair<string, int>("23", 23),
-                    new KeyValuePair<string, int>("27", 27),
+                    new KeyValuePair<string, int>("prefix[23]", 23),
+                    new KeyValuePair<string, int>("prefix[27]", 27),
                 }.OrderBy(kvp => kvp.Key),
                 strategy.KeyMappings.OrderBy(kvp => kvp.Key));
         }
@@ -532,15 +532,14 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 
             public override bool Equals(object obj)
             {
-                var other = obj as ModelWithProperties;
-                return other != null &&
+                return obj is ModelWithProperties other &&
                     Id == other.Id &&
                     string.Equals(Name, other.Name, StringComparison.Ordinal);
             }
 
             public override int GetHashCode()
             {
-                int nameCode = Name == null ? 0 : Name.GetHashCode();
+                var nameCode = Name == null ? 0 : Name.GetHashCode();
                 return nameCode ^ Id.GetHashCode();
             }
 

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

@@ -89,12 +89,12 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
                     "[14]property1[15]property2",
                     "prefix.property1[13]",
                     "prefix[14][15]",
-                    ".property5",
-                    ".property6Value",
+                    "property5",
+                    "property6Value",
                     "prefix.property2",
                     "prefix.propertyValue",
-                    ".property7.property8",
-                    ".property9.property10Value",
+                    "property7.property8",
+                    "property9.property10Value",
                 };
             }
         }

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

@@ -17,6 +17,12 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
     {
         private static readonly Dictionary<string, StringValues> _backingStore = new Dictionary<string, StringValues>
         {
+            // Reviewers: A fair number of cases in the following dataset seem impossible for jQuery.ajax() to send
+            // given how $.ajax() and $.param() are defined i.e. $.param() won't add a bare name after ']'. Also, the
+            // names we generate for <input/> elements are always valid. Should we remove these weird / invalid cases
+            // e.g. normalizing "property[]Value"? (That normalizes to "propertyValue".) See also
+            // https://github.com/jquery/jquery/blob/1ea092a54b00aa4d902f4e22ada3854d195d4a18/src/serialize.js#L13-L92
+            // The alternative is to handle "[]name" and "[index]name" cases while normalizing keys.
             { "[]", new[] { "found" } },
             { "[]property1", new[] { "found" } },
             { "property2[]", new[] { "found" } },
@@ -57,12 +63,12 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Test
                     "[14]property1[15]property2",
                     "prefix.property1[13]",
                     "prefix[14][15]",
-                    ".property5",
-                    ".property6Value",
+                    "property5",
+                    "property6Value",
                     "prefix.property2",
                     "prefix.propertyValue",
-                    ".property7.property8",
-                    ".property9.property10Value",
+                    "property7.property8",
+                    "property9.property10Value",
                 };
             }
         }

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

@@ -450,15 +450,26 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             }
         }
 
+        public static TheoryData<string> ComplexType_ImpliedPrefixData
+        {
+            get
+            {
+                return new TheoryData<string>
+                {
+                    "?[key0].Id=10",
+                    "?[0].Key=key0&[0].Value.Id=10",
+                    "?index=low&[low].Key=key0&[low].Value.Id=10",
+                    "?parameter[key0].Id=10",
+                    "?parameter[0].Key=key0&parameter[0].Value.Id=10",
+                    "?parameter.index=low&parameter[low].Key=key0&parameter[low].Value.Id=10",
+                    "?parameter.index=index&parameter[index].Key=key0&parameter[index].Value.Id=10",
+                };
+            }
+        }
+
         [Theory]
-        [InlineData("?[key0].Id=10")]
-        [InlineData("?[0].Key=key0&[0].Value.Id=10")]
-        [InlineData("?index=low&[low].Key=key0&[low].Value.Id=10")]
-        [InlineData("?parameter[key0].Id=10")]
-        [InlineData("?parameter[0].Key=key0&parameter[0].Value.Id=10")]
-        [InlineData("?parameter.index=low&parameter[low].Key=key0&parameter[low].Value.Id=10")]
-        [InlineData("?parameter.index=index&parameter[index].Key=key0&parameter[index].Value.Id=10")]
-        public async Task DictionaryModelBinder_BindsDictionaryOfComplexType_ImpliedPrefix_Success(string queryString)
+        [MemberData(nameof(ComplexType_ImpliedPrefixData))]
+        public async Task DictionaryModelBinder_BindsDictionaryOfComplexType_WithImpliedPrefix(string queryString)
         {
             // Arrange
             var parameterBinder = ModelBindingTestHelper.GetParameterBinder();
@@ -490,11 +501,168 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
         }
 
         [Theory]
-        [InlineData("?prefix[key0].Id=10")]
-        [InlineData("?prefix[0].Key=key0&prefix[0].Value.Id=10")]
-        [InlineData("?prefix.index=low&prefix[low].Key=key0&prefix[low].Value.Id=10")]
-        [InlineData("?prefix.index=index&prefix[index].Key=key0&prefix[index].Value.Id=10")]
-        public async Task DictionaryModelBinder_BindsDictionaryOfComplexType_ExplicitPrefix_Success(
+        [InlineData("?[key0][Id]=10")] // Both key segments will be rewritten.
+        [InlineData("?[0][Key]=key0&[0][Value][Id]=10")]
+        [InlineData("?parameter[key0][Id]=10")]
+        [InlineData("?parameter[0][Key]=key0&parameter[0][Value][Id]=10")]
+        [MemberData(nameof(ComplexType_ImpliedPrefixData))]
+        public async Task DictionaryModelBinder_BindsDictionaryOfComplexType_WithImpliedPrefixAndJQuery(
+            string queryString)
+        {
+            // Arrange
+            var expectedDictionary = new Dictionary<string, Person> { { "key0", new Person { Id = 10 } } };
+            var testContext = ModelBindingTestHelper.GetTestContext(
+                request => request.QueryString = new QueryString(queryString),
+                // Add JQueryQueryStringValueProviderFactory after default factories.
+                options => options.ValueProviderFactories.Add(new JQueryQueryStringValueProviderFactory()));
+
+            var modelState = testContext.ModelState;
+            var parameterBinder = ModelBindingTestHelper.GetParameterBinder(testContext.HttpContext.RequestServices);
+            var parameter = new ParameterDescriptor()
+            {
+                Name = "parameter",
+                ParameterType = typeof(Dictionary<string, Person>)
+            };
+
+            // Act
+            var modelBindingResult = await parameterBinder.BindModelAsync(parameter, testContext);
+
+            // Assert
+            Assert.True(modelBindingResult.IsModelSet);
+
+            var model = Assert.IsType<Dictionary<string, Person>>(modelBindingResult.Model);
+            Assert.Equal(expectedDictionary, model);
+
+            Assert.NotEmpty(modelState);
+            Assert.Equal(0, modelState.ErrorCount);
+            Assert.True(modelState.IsValid);
+        }
+
+        [Theory]
+        [InlineData("?[key0][Id]=10")] // Both key segments will be rewritten.
+        [InlineData("?[0][Key]=key0&[0][Value][Id]=10")]
+        [InlineData("?parameter[key0][Id]=10")]
+        [InlineData("?parameter[0][Key]=key0&parameter[0][Value][Id]=10")]
+        [MemberData(nameof(ComplexType_ImpliedPrefixData))]
+        public async Task DictionaryModelBinder_BindsDictionaryOfComplexType_WithImpliedPrefixAndJQueryFirst(
+            string queryString)
+        {
+            // Arrange
+            var expectedDictionary = new Dictionary<string, Person> { { "key0", new Person { Id = 10 } } };
+            var testContext = ModelBindingTestHelper.GetTestContext(
+                request => request.QueryString = new QueryString(queryString),
+                // Add JQueryQueryStringValueProviderFactory before default factories.
+                options => options.ValueProviderFactories.Insert(0, new JQueryQueryStringValueProviderFactory()));
+
+            var modelState = testContext.ModelState;
+            var parameterBinder = ModelBindingTestHelper.GetParameterBinder(testContext.HttpContext.RequestServices);
+            var parameter = new ParameterDescriptor()
+            {
+                Name = "parameter",
+                ParameterType = typeof(Dictionary<string, Person>)
+            };
+
+            // Act
+            var modelBindingResult = await parameterBinder.BindModelAsync(parameter, testContext);
+
+            // Assert
+            Assert.True(modelBindingResult.IsModelSet);
+
+            var model = Assert.IsType<Dictionary<string, Person>>(modelBindingResult.Model);
+            Assert.Equal(expectedDictionary, model);
+
+            Assert.NotEmpty(modelState);
+            Assert.Equal(0, modelState.ErrorCount);
+            Assert.True(modelState.IsValid);
+        }
+
+        [Theory]
+        [InlineData("?[42][Id]=10")] // Only Id segment will be rewritten.
+        [InlineData("?parameter[42][Id]=10")]
+        public async Task DictionaryModelBinder_BindsDictionaryOfComplexType_WithImpliedPrefixIntegralKeysAndJQuery(
+            string queryString)
+        {
+            // Arrange
+            var expectedDictionary = new Dictionary<string, Person> { { "42", new Person { Id = 10 } } };
+            var testContext = ModelBindingTestHelper.GetTestContext(
+                request => request.QueryString = new QueryString(queryString),
+                // Add JQueryQueryStringValueProviderFactory after default factories.
+                options => options.ValueProviderFactories.Add(new JQueryQueryStringValueProviderFactory()));
+
+            var modelState = testContext.ModelState;
+            var parameterBinder = ModelBindingTestHelper.GetParameterBinder(testContext.HttpContext.RequestServices);
+            var parameter = new ParameterDescriptor()
+            {
+                Name = "parameter",
+                ParameterType = typeof(Dictionary<string, Person>)
+            };
+
+            // Act
+            var modelBindingResult = await parameterBinder.BindModelAsync(parameter, testContext);
+
+            // Assert
+            Assert.True(modelBindingResult.IsModelSet);
+
+            var model = Assert.IsType<Dictionary<string, Person>>(modelBindingResult.Model);
+            Assert.Equal(expectedDictionary, model);
+
+            Assert.NotEmpty(modelState);
+            Assert.Equal(0, modelState.ErrorCount);
+            Assert.True(modelState.IsValid);
+        }
+
+        [Theory]
+        [InlineData("?[42][Id]=10")] // Only Id segment will be rewritten.
+        [InlineData("?parameter[42][Id]=10")]
+        public async Task DictionaryModelBinder_BindsDictionaryOfComplexType_WithImpliedPrefixIntegralKeysAndJQueryFirst(
+            string queryString)
+        {
+            // Arrange
+            var expectedDictionary = new Dictionary<string, Person> { { "42", new Person { Id = 10 } } };
+            var testContext = ModelBindingTestHelper.GetTestContext(
+                request => request.QueryString = new QueryString(queryString),
+                // Add JQueryQueryStringValueProviderFactory before default factories.
+                options => options.ValueProviderFactories.Insert(0, new JQueryQueryStringValueProviderFactory()));
+
+            var modelState = testContext.ModelState;
+            var parameterBinder = ModelBindingTestHelper.GetParameterBinder(testContext.HttpContext.RequestServices);
+            var parameter = new ParameterDescriptor()
+            {
+                Name = "parameter",
+                ParameterType = typeof(Dictionary<string, Person>)
+            };
+
+            // Act
+            var modelBindingResult = await parameterBinder.BindModelAsync(parameter, testContext);
+
+            // Assert
+            Assert.True(modelBindingResult.IsModelSet);
+
+            var model = Assert.IsType<Dictionary<string, Person>>(modelBindingResult.Model);
+            Assert.Equal(expectedDictionary, model);
+
+            Assert.NotEmpty(modelState);
+            Assert.Equal(0, modelState.ErrorCount);
+            Assert.True(modelState.IsValid);
+        }
+
+        public static TheoryData<string> ComplexType_ExplicitPrefixData
+        {
+            get
+            {
+                return new TheoryData<string>
+                {
+                    "?prefix[key0].Id=10",
+                    "?prefix[0].Key=key0&prefix[0].Value.Id=10",
+                    "?prefix.index=low&prefix[low].Key=key0&prefix[low].Value.Id=10",
+                    "?prefix.index=index&prefix[index].Key=key0&prefix[index].Value.Id=10",
+                };
+            }
+        }
+
+        [Theory]
+        [MemberData(nameof(ComplexType_ExplicitPrefixData))]
+        public async Task DictionaryModelBinder_BindsDictionaryOfComplexType_WithExplicitPrefix(
             string queryString)
         {
             // Arrange
@@ -530,6 +698,45 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.True(modelState.IsValid);
         }
 
+        [Theory]
+        [InlineData("?prefix[key0][Id]=10")]
+        [MemberData(nameof(ComplexType_ExplicitPrefixData))]
+        public async Task DictionaryModelBinder_BindsDictionaryOfComplexType_WithExplicitPrefixAndJQuery(
+            string queryString)
+        {
+            // Arrange
+            var testContext = ModelBindingTestHelper.GetTestContext(
+                request => request.QueryString = new QueryString(queryString),
+                // Add JQueryQueryStringValueProviderFactory after default factories.
+                options => options.ValueProviderFactories.Add(new JQueryQueryStringValueProviderFactory()));
+
+            var parameterBinder = ModelBindingTestHelper.GetParameterBinder(testContext.HttpContext.RequestServices);
+            var parameter = new ParameterDescriptor()
+            {
+                Name = "parameter",
+                BindingInfo = new BindingInfo()
+                {
+                    BinderModelName = "prefix",
+                },
+                ParameterType = typeof(Dictionary<string, Person>)
+            };
+
+            var modelState = testContext.ModelState;
+
+            // Act
+            var modelBindingResult = await parameterBinder.BindModelAsync(parameter, testContext);
+
+            // Assert
+            Assert.True(modelBindingResult.IsModelSet);
+
+            var model = Assert.IsType<Dictionary<string, Person>>(modelBindingResult.Model);
+            Assert.Equal(new Dictionary<string, Person> { { "key0", new Person { Id = 10 } }, }, model);
+
+            Assert.NotEmpty(modelState);
+            Assert.Equal(0, modelState.ErrorCount);
+            Assert.True(modelState.IsValid);
+        }
+
         [Theory]
         [InlineData("?[key0].Id=100")]
         [InlineData("?[0].Key=key0&[0].Value.Id=100")]
@@ -610,6 +817,202 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.True(modelState.IsValid);
         }
 
+        public static TheoryData<string> CollectionType_ImpliedPrefixData
+        {
+            get
+            {
+                return new TheoryData<string>
+                {
+                    "?[key0]=10&[key0]=11",
+                    "?[key0][0]=10&[key0][1]=11",
+                    "?[0].Key=key0&[0].Value[0]=10&[0].Value[1]=11",
+                    "?index=low&[low].Key=key0&[low].Value[0]=10&[low].Value[1]=11",
+                    "?parameter[key0]=10&parameter[key0]=11",
+                    "?parameter[key0][0]=10&parameter[key0][1]=11",
+                    "?parameter[0].Key=key0&parameter[0].Value[0]=10&parameter[0].Value[1]=11",
+                    "?parameter.index=low&parameter[low].Key=key0&parameter[low].Value[0]=10&parameter[low].Value[1]=11",
+                    "?parameter.index=index&parameter[index].Key=key0&parameter[index].Value[0]=10&parameter[index].Value[1]=11",
+                };
+            }
+        }
+
+        [Theory]
+        [MemberData(nameof(CollectionType_ImpliedPrefixData))]
+        public async Task DictionaryModelBinder_BindsDictionaryOfCollectionType_WithImpliedPrefix(string queryString)
+        {
+            // Arrange
+            var expectedDictionary = new Dictionary<string, string[]> { { "key0", new[] { "10", "11" } } };
+            var parameterBinder = ModelBindingTestHelper.GetParameterBinder();
+            var parameter = new ParameterDescriptor()
+            {
+                Name = "parameter",
+                ParameterType = typeof(Dictionary<string, string[]>)
+            };
+
+            var testContext = ModelBindingTestHelper.GetTestContext(
+                request => request.QueryString = new QueryString(queryString));
+            var modelState = testContext.ModelState;
+
+            // Act
+            var modelBindingResult = await parameterBinder.BindModelAsync(parameter, testContext);
+
+            // Assert
+            Assert.True(modelBindingResult.IsModelSet);
+
+            var model = Assert.IsType<Dictionary<string, string[]>>(modelBindingResult.Model);
+            Assert.Equal(expectedDictionary, model);
+
+            Assert.NotEmpty(modelState);
+            Assert.Equal(0, modelState.ErrorCount);
+            Assert.True(modelState.IsValid);
+        }
+
+        [Theory]
+        [MemberData(nameof(CollectionType_ImpliedPrefixData))]
+        public async Task DictionaryModelBinder_BindsDictionaryOfCollectionType_WithImpliedPrefixAndJQuery(
+            string queryString)
+        {
+            // Arrange
+            var expectedDictionary = new Dictionary<string, string[]> { { "key0", new[] { "10", "11" } } };
+            var testContext = ModelBindingTestHelper.GetTestContext(
+                request => request.QueryString = new QueryString(queryString),
+                // Add JQueryQueryStringValueProviderFactory after default factories.
+                options => options.ValueProviderFactories.Add(new JQueryQueryStringValueProviderFactory()));
+
+            var modelState = testContext.ModelState;
+            var parameterBinder = ModelBindingTestHelper.GetParameterBinder(testContext.HttpContext.RequestServices);
+            var parameter = new ParameterDescriptor()
+            {
+                Name = "parameter",
+                ParameterType = typeof(Dictionary<string, string[]>)
+            };
+
+            // Act
+            var modelBindingResult = await parameterBinder.BindModelAsync(parameter, testContext);
+
+            // Assert
+            Assert.True(modelBindingResult.IsModelSet);
+
+            var model = Assert.IsType<Dictionary<string, string[]>>(modelBindingResult.Model);
+            Assert.Equal(expectedDictionary, model);
+
+            Assert.NotEmpty(modelState);
+            Assert.Equal(0, modelState.ErrorCount);
+            Assert.True(modelState.IsValid);
+        }
+
+        [Theory]
+        [MemberData(nameof(CollectionType_ImpliedPrefixData))]
+        public async Task DictionaryModelBinder_BindsDictionaryOfCollectionType_WithImpliedPrefixAndJQueryFirst(
+            string queryString)
+        {
+            // Arrange
+            var expectedDictionary = new Dictionary<string, string[]> { { "key0", new[] { "10", "11" } } };
+            var testContext = ModelBindingTestHelper.GetTestContext(
+                request => request.QueryString = new QueryString(queryString),
+                // Add JQueryQueryStringValueProviderFactory before default factories.
+                options => options.ValueProviderFactories.Insert(0, new JQueryQueryStringValueProviderFactory()));
+
+            var modelState = testContext.ModelState;
+            var parameterBinder = ModelBindingTestHelper.GetParameterBinder(testContext.HttpContext.RequestServices);
+            var parameter = new ParameterDescriptor()
+            {
+                Name = "parameter",
+                ParameterType = typeof(Dictionary<string, string[]>)
+            };
+
+            // Act
+            var modelBindingResult = await parameterBinder.BindModelAsync(parameter, testContext);
+
+            // Assert
+            Assert.True(modelBindingResult.IsModelSet);
+
+            var model = Assert.IsType<Dictionary<string, string[]>>(modelBindingResult.Model);
+            Assert.Equal(expectedDictionary, model);
+
+            Assert.NotEmpty(modelState);
+            Assert.Equal(0, modelState.ErrorCount);
+            Assert.True(modelState.IsValid);
+        }
+
+        [Theory]
+        [InlineData("?[42]=10&[42]=11")]
+        [InlineData("?[42][]=10&[42][]=11")]
+        [InlineData("?[42][0]=10&[42][1]=11")]
+        [InlineData("?parameter[42]=10&parameter[42]=11")]
+        [InlineData("?parameter[42][]=10&parameter[42][]=11")]
+        [InlineData("?parameter[42][0]=10&parameter[42][1]=11")]
+        public async Task DictionaryModelBinder_BindsDictionaryOfCollectionType_WithImpliedPrefixIntegralKeysAndJQuery(
+            string queryString)
+        {
+            // Arrange
+            var expectedDictionary = new Dictionary<string, string[]> { { "42", new[] { "10", "11" } } };
+            var testContext = ModelBindingTestHelper.GetTestContext(
+                request => request.QueryString = new QueryString(queryString),
+                // Add JQueryQueryStringValueProviderFactory after default factories.
+                options => options.ValueProviderFactories.Add(new JQueryQueryStringValueProviderFactory()));
+
+            var modelState = testContext.ModelState;
+            var parameterBinder = ModelBindingTestHelper.GetParameterBinder(testContext.HttpContext.RequestServices);
+            var parameter = new ParameterDescriptor()
+            {
+                Name = "parameter",
+                ParameterType = typeof(Dictionary<string, string[]>)
+            };
+
+            // Act
+            var modelBindingResult = await parameterBinder.BindModelAsync(parameter, testContext);
+
+            // Assert
+            Assert.True(modelBindingResult.IsModelSet);
+
+            var model = Assert.IsType<Dictionary<string, string[]>>(modelBindingResult.Model);
+            Assert.Equal(expectedDictionary, model);
+
+            Assert.NotEmpty(modelState);
+            Assert.Equal(0, modelState.ErrorCount);
+            Assert.True(modelState.IsValid);
+        }
+
+        [Theory]
+        [InlineData("?[42]=10&[42]=11")]
+        [InlineData("?[42][]=10&[42][]=11")]
+        [InlineData("?[42][0]=10&[42][1]=11")]
+        [InlineData("?parameter[42]=10&parameter[42]=11")]
+        [InlineData("?parameter[42][]=10&parameter[42][]=11")]
+        [InlineData("?parameter[42][0]=10&parameter[42][1]=11")]
+        public async Task DictionaryModelBinder_BindsDictionaryOfCollectionType_WithImpliedPrefixIntegralKeysAndJQueryFirst(
+            string queryString)
+        {
+            // Arrange
+            var expectedDictionary = new Dictionary<string, string[]> { { "42", new[] { "10", "11" } } };
+            var testContext = ModelBindingTestHelper.GetTestContext(
+                request => request.QueryString = new QueryString(queryString),
+                // Add JQueryQueryStringValueProviderFactory before default factories.
+                options => options.ValueProviderFactories.Insert(0, new JQueryQueryStringValueProviderFactory()));
+
+            var modelState = testContext.ModelState;
+            var parameterBinder = ModelBindingTestHelper.GetParameterBinder(testContext.HttpContext.RequestServices);
+            var parameter = new ParameterDescriptor()
+            {
+                Name = "parameter",
+                ParameterType = typeof(Dictionary<string, string[]>)
+            };
+
+            // Act
+            var modelBindingResult = await parameterBinder.BindModelAsync(parameter, testContext);
+
+            // Assert
+            Assert.True(modelBindingResult.IsModelSet);
+
+            var model = Assert.IsType<Dictionary<string, string[]>>(modelBindingResult.Model);
+            Assert.Equal(expectedDictionary, model);
+
+            Assert.NotEmpty(modelState);
+            Assert.Equal(0, modelState.ErrorCount);
+            Assert.True(modelState.IsValid);
+        }
+
         // parameter type, query string, expected type
         public static TheoryData<Type, string, Type> DictionaryTypeData
         {