Fix for #1722 - FromHeader does not respect default value

This change adds support for our three-valued logic to the default value
handling part of the MutableObjectModelBinder.

The issue is that we want to look up a default value when a 'greedy' model
binder returns true but doesn't find a value.

We also don't want to call the property setter unless there is:
1). A value from model binding OR
2). A default value

src/Microsoft.AspNet.Mvc.Core/DefaultControllerActionArgumentBinder.cs

@@ -88,7 +88,8 @@ namespace Microsoft.AspNet.Mvc
             {
                 var parameterType = parameter.ModelType;
                 var modelBindingContext = GetModelBindingContext(parameter, actionContext, operationBindingContext);
-                if (await bindingContext.ModelBinder.BindModelAsync(modelBindingContext))
+                if (await bindingContext.ModelBinder.BindModelAsync(modelBindingContext) &&
+                    modelBindingContext.IsModelSet)
                 {
                     arguments[parameter.PropertyName] = modelBindingContext.Model;
                 }

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

@@ -27,11 +27,10 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
                                                                          propertyMetadata);
 
                     // bind and propagate the values
-                    // If we can't bind, then leave the result missing (don't add a null).
+                    // If we can't bind then leave the result missing (don't add a null).
                     if (await bindingContext.OperationBindingContext.ModelBinder.BindModelAsync(propertyBindingContext))
                     {
-                        var result = new ComplexModelDtoResult(propertyBindingContext.Model,
+                        var result = ComplexModelDtoResult.FromBindingContext(propertyBindingContext);
-                                                               propertyBindingContext.ValidationNode);
                         dto.Results[propertyMetadata] = result;
                     }
                 }

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

@@ -5,15 +5,25 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
 {
     public sealed class ComplexModelDtoResult
     {
-        public ComplexModelDtoResult(object model,
+        public static ComplexModelDtoResult FromBindingContext([NotNull] ModelBindingContext context)
-                                    [NotNull] ModelValidationNode validationNode)
+        {
+            return new ComplexModelDtoResult(context.Model, context.IsModelSet, context.ValidationNode);
+        }
+
+        public ComplexModelDtoResult(
+            object model,
+            bool isModelBound,
+            [NotNull] ModelValidationNode validationNode)
         {
             Model = model;
+            IsModelBound = isModelBound;
             ValidationNode = validationNode;
         }
 
-        public object Model { get; private set; }
+        public bool IsModelBound { get; }
 
-        public ModelValidationNode ValidationNode { get; private set; }
+        public object Model { get; set; }
+
+        public ModelValidationNode ValidationNode { get; set; }
     }
 }

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

@@ -291,10 +291,19 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             };
         }
 
-        private static object GetPropertyDefaultValue(PropertyInfo propertyInfo)
+        private static bool TryGetPropertyDefaultValue(PropertyInfo propertyInfo, out object value)
         {
-            var attr = propertyInfo.GetCustomAttribute<DefaultValueAttribute>();
+            var attribute = propertyInfo.GetCustomAttribute<DefaultValueAttribute>();
-            return (attr != null) ? attr.Value : null;
+            if (attribute == null)
+            {
+                value = null;
+                return false;
+            }
+            else
+            {
+                value = attribute.Value;
+                return true;
+            }
         }
 
         internal static PropertyValidationInfo GetPropertyValidationInfo(ModelBindingContext bindingContext)
@@ -345,7 +354,8 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             var validationInfo = GetPropertyValidationInfo(bindingContext);
 
             // Eliminate provided properties from requiredProperties; leaving just *missing* required properties.
-            validationInfo.RequiredProperties.ExceptWith(dto.Results.Select(r => r.Key.PropertyName));
+            var boundProperties = dto.Results.Where(p => p.Value.IsModelBound).Select(p => p.Key.PropertyName);
+            validationInfo.RequiredProperties.ExceptWith(boundProperties);
 
             foreach (var missingRequiredProperty in validationInfo.RequiredProperties)
             {
@@ -407,7 +417,17 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
                 return;
             }
 
-            var value = dtoResult.Model ?? GetPropertyDefaultValue(property);
+            object value;
+            var hasDefaultValue = false;
+            if (dtoResult.IsModelBound)
+            {
+                value = dtoResult.Model;
+            }
+            else
+            {
+                hasDefaultValue = TryGetPropertyDefaultValue(property, out value);
+            }
+
             propertyMetadata.Model = value;
 
             // 'Required' validators need to run first so that we can provide useful error messages if
@@ -429,6 +449,13 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
                 }
             }
 
+            if (!dtoResult.IsModelBound && !hasDefaultValue)
+            {
+                // If we don't have a value, don't set it on the model and trounce a pre-initialized
+                // value.
+                return;
+            }
+
             if (value != null || property.PropertyType.AllowsNullValue())
             {
                 try

test/Microsoft.AspNet.Mvc.Core.Test/ParameterBinding/ControllerActionArgumentBinderTests.cs

@@ -183,6 +183,11 @@ namespace Microsoft.AspNet.Mvc.Core.Test
             var binder = new Mock<IModelBinder>();
             binder
                 .Setup(b => b.BindModelAsync(It.IsAny<ModelBindingContext>()))
+                .Callback<ModelBindingContext>(c =>
+                {
+                    // This value won't go into the arguments, because we return false.
+                    c.Model = "Hello";
+                })
                 .Returns(Task.FromResult(result: false));
 
             var actionContext = new ActionContext(
@@ -211,6 +216,59 @@ namespace Microsoft.AspNet.Mvc.Core.Test
             Assert.Empty(result);
         }
 
+        [Fact]
+        public async Task GetActionArgumentsAsync_DoesNotAddActionArguments_IfBinderDoesNotSetModel()
+        {
+            // Arrange
+            Func<object, int> method = foo => 1;
+            var actionDescriptor = new ControllerActionDescriptor
+            {
+                MethodInfo = method.Method,
+                Parameters = new List<ParameterDescriptor>
+                {
+                    new ParameterDescriptor
+                    {
+                        Name = "foo",
+                        ParameterType = typeof(object),
+                    }
+                }
+            };
+
+            var binder = new Mock<IModelBinder>();
+            binder
+                .Setup(b => b.BindModelAsync(It.IsAny<ModelBindingContext>()))
+                .Callback<ModelBindingContext>(c =>
+                {
+                    Assert.False(c.IsModelSet);
+                })
+                .Returns(Task.FromResult(result: true));
+
+            var actionContext = new ActionContext(
+                new RouteContext(Mock.Of<HttpContext>()),
+                actionDescriptor)
+            {
+                Controller = Mock.Of<object>(),
+            };
+
+            var actionBindingContext = new ActionBindingContext()
+            {
+                ModelBinder = binder.Object,
+            };
+
+            var inputFormattersProvider = new Mock<IInputFormattersProvider>();
+            inputFormattersProvider
+                .SetupGet(o => o.InputFormatters)
+                .Returns(new List<IInputFormatter>());
+
+            var invoker = new DefaultControllerActionArgumentBinder(new DataAnnotationsModelMetadataProvider());
+
+            // Act
+            var result = await invoker.GetActionArgumentsAsync(actionContext, actionBindingContext);
+
+            // Assert
+            Assert.Empty(result);
+        }
+
         [Fact]
         public async Task GetActionArgumentsAsync_AddsActionArguments_IfBinderReturnsTrue()
         {

test/Microsoft.AspNet.Mvc.FunctionalTests/Compiler/Resources/UpdateDealerVehicle_UpdateSuccessful.txt

@@ -20,5 +20,5 @@
 </div>
 
 <footer>
-Tracked by 
+Tracked by default-tracking-id
 </footer>

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

@@ -99,6 +99,36 @@ namespace Microsoft.AspNet.Mvc.FunctionalTests
             Assert.Empty(result.ModelStateErrors);
         }
 
+        // There should be no model state error for a top-level object
+        [Theory]
+        [InlineData("transactionId1234", "1e331f25-0869-4c87-8a94-64e6e40cb5a0")]
+        public async Task FromHeader_BindHeader_ToString_OnParameter_NoValues_DefaultValue(
+            string headerName,
+            string headerValue)
+        {
+            // Arrange
+            var server = TestServer.Create(_services, _app);
+            var client = server.CreateClient();
+
+            var request = new HttpRequestMessage(
+                HttpMethod.Get,
+                "http://localhost/Blog/BindToStringParameterDefaultValue");
+            // Intentionally not setting a header value
+
+            // Act
+            var response = await client.SendAsync(request);
+
+            // Assert
+            Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+
+            var body = await response.Content.ReadAsStringAsync();
+            var result = JsonConvert.DeserializeObject<Result>(body);
+
+            Assert.Equal("default-value", result.HeaderValue);
+            Assert.Null(result.HeaderValues);
+            Assert.Empty(result.ModelStateErrors);
+        }
+
         // The action that this test hits will echo back the model-bound values
         [Theory]
         [InlineData("transactionIds", "1e331f25-0869-4c87-8a94-64e6e40cb5a0")]
@@ -187,6 +217,70 @@ namespace Microsoft.AspNet.Mvc.FunctionalTests
             Assert.Equal("Title", error);
         }
 
+        // This model sets a value for 'Title', and the model binder won't trounce it.
+        //
+        // There's no validation error because we validate the initialized value.
+        [Fact]
+        public async Task FromHeader_BindHeader_ToModel_NoValues_InitializedValue_ValidationError()
+        {
+            // Arrange
+            var server = TestServer.Create(_services, _app);
+            var client = server.CreateClient();
+
+            var request = new HttpRequestMessage(
+                HttpMethod.Get,
+                "http://localhost/Blog/BindToModelWithInitializedValue?author=Marvin");
+
+            // Intentionally not setting a title or tags
+
+            // Act
+            var response = await client.SendAsync(request);
+
+            // Assert
+            Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+
+            var body = await response.Content.ReadAsStringAsync();
+            var result = JsonConvert.DeserializeObject<Result>(body);
+
+            Assert.Equal("How to Make Soup", result.HeaderValue);
+            Assert.Equal<string>(new[] { "Cooking" }, result.HeaderValues);
+
+            var error = Assert.Single(result.ModelStateErrors);
+            Assert.Equal("Title", error);
+        }
+
+        // This model uses default value for 'Title'.
+        //
+        // There's no validation error because we validate the default value.
+        [Fact]
+        public async Task FromHeader_BindHeader_ToModel_NoValues_DefaultValue_NoValidationError()
+        {
+            // Arrange
+            var server = TestServer.Create(_services, _app);
+            var client = server.CreateClient();
+
+            var request = new HttpRequestMessage(
+                HttpMethod.Get,
+                "http://localhost/Blog/BindToModelWithDefaultValue?author=Marvin");
+
+            // Intentionally not setting a title or tags
+
+            // Act
+            var response = await client.SendAsync(request);
+
+            // Assert
+            Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+
+            var body = await response.Content.ReadAsStringAsync();
+            var result = JsonConvert.DeserializeObject<Result>(body);
+
+            Assert.Equal("How to Make Soup", result.HeaderValue);
+            Assert.Equal<string>(new[] { "Cooking" }, result.HeaderValues);
+
+            var error = Assert.Single(result.ModelStateErrors);
+            Assert.Equal("Title", error);
+        }
+
         private class Result
         {
             public string HeaderValue { get; set; }

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

@@ -14,10 +14,14 @@ namespace Microsoft.AspNet.Mvc.ModelBinding.Test
             var validationNode = GetValidationNode();
 
             // Act
-            var result = new ComplexModelDtoResult("some string", validationNode);
+            var result = new ComplexModelDtoResult(
+                "some string", 
+                isModelBound: true, 
+                validationNode: validationNode);
 
             // Assert
             Assert.Equal("some string", result.Model);
+            Assert.True(result.IsModelBound);
             Assert.Equal(validationNode, result.ValidationNode);
         }
 

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

@@ -583,7 +583,9 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
                 "ValueTypeRequired",
                 "FirstName",
                 "LastName",
-                "PropertyWithDefaultValue"
+                "PropertyWithDefaultValue",
+                "PropertyWithInitializedValue",
+                "PropertyWithInitializedValueAndDefault",
             };
             var bindingContext = new ModelBindingContext
             {
@@ -751,7 +753,10 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             var dto = new ComplexModelDto(containerMetadata, containerMetadata.Properties);
 
             var nameProperty = dto.PropertyMetadata.Single(o => o.PropertyName == "Name");
-            dto.Results[nameProperty] = new ComplexModelDtoResult("John Doe", new ModelValidationNode(nameProperty, ""));
+            dto.Results[nameProperty] = new ComplexModelDtoResult(
+                "John Doe",
+                isModelBound: true,
+                validationNode: new ModelValidationNode(nameProperty, ""));
 
             var testableBinder = new TestableMutableObjectModelBinder();
 
@@ -805,14 +810,18 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             var testableBinder = new TestableMutableObjectModelBinder();
 
             var propertyMetadata = dto.PropertyMetadata.Single(o => o.PropertyName == "Name");
-            dto.Results[propertyMetadata] =
+            dto.Results[propertyMetadata] = new ComplexModelDtoResult(
-                new ComplexModelDtoResult("John Doe", new ModelValidationNode(propertyMetadata, "theModel.Name"));
+                "John Doe",
+                isModelBound: true,
+                validationNode: new ModelValidationNode(propertyMetadata, "theModel.Name"));
 
             // Attempt to set non-Nullable property to null. BindRequiredAttribute should not be relevant in this
             // case because the binding exists.
             propertyMetadata = dto.PropertyMetadata.Single(o => o.PropertyName == "Age");
-            dto.Results[propertyMetadata] =
+            dto.Results[propertyMetadata] = new ComplexModelDtoResult(
-                new ComplexModelDtoResult(null, new ModelValidationNode(propertyMetadata, "theModel.Age"));
+                null,
+                isModelBound: true,
+                validationNode: new ModelValidationNode(propertyMetadata, "theModel.Age"));
 
             // Act; must also Validate because null-check error handler is late-bound
             testableBinder.ProcessDto(bindingContext, dto);
@@ -894,11 +903,16 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
 
             // Make Age valid and City invalid.
             var propertyMetadata = dto.PropertyMetadata.Single(p => p.PropertyName == "Age");
-            dto.Results[propertyMetadata] =
+            dto.Results[propertyMetadata] = new ComplexModelDtoResult(
-                new ComplexModelDtoResult(23, new ModelValidationNode(propertyMetadata, "theModel.Age"));
+                23,
+                isModelBound: true,
+                validationNode: new ModelValidationNode(propertyMetadata, "theModel.Age"));
+
             propertyMetadata = dto.PropertyMetadata.Single(p => p.PropertyName == "City");
-            dto.Results[propertyMetadata] =
+            dto.Results[propertyMetadata] = new ComplexModelDtoResult(
-                new ComplexModelDtoResult(null, new ModelValidationNode(propertyMetadata, "theModel.City"));
+                null,
+                isModelBound: true,
+                validationNode: new ModelValidationNode(propertyMetadata, "theModel.City"));
 
             // Act
             testableBinder.ProcessDto(bindingContext, dto);
@@ -963,8 +977,10 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
 
             // Make ValueTypeRequired invalid.
             var propertyMetadata = dto.PropertyMetadata.Single(p => p.PropertyName == "ValueTypeRequired");
-            dto.Results[propertyMetadata] =
+            dto.Results[propertyMetadata] = new ComplexModelDtoResult(
-                new ComplexModelDtoResult(null, new ModelValidationNode(propertyMetadata, "theModel.ValueTypeRequired"));
+                null,
+                isModelBound: true,
+                validationNode: new ModelValidationNode(propertyMetadata, "theModel.ValueTypeRequired"));
 
             // Act
             testableBinder.ProcessDto(bindingContext, dto);
@@ -999,9 +1015,17 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             var dto = new ComplexModelDto(containerMetadata, containerMetadata.Properties);
 
             var firstNameProperty = dto.PropertyMetadata.Single(o => o.PropertyName == "FirstName");
-            dto.Results[firstNameProperty] = new ComplexModelDtoResult("John", new ModelValidationNode(firstNameProperty, ""));
+            dto.Results[firstNameProperty] = new ComplexModelDtoResult(
+                "John",
+                isModelBound: true,
+                validationNode: new ModelValidationNode(firstNameProperty, ""));
+
             var lastNameProperty = dto.PropertyMetadata.Single(o => o.PropertyName == "LastName");
-            dto.Results[lastNameProperty] = new ComplexModelDtoResult("Doe", new ModelValidationNode(lastNameProperty, ""));
+            dto.Results[lastNameProperty] = new ComplexModelDtoResult(
+                "Doe",
+                isModelBound: true,
+                validationNode: new ModelValidationNode(lastNameProperty, ""));
+
             var dobProperty = dto.PropertyMetadata.Single(o => o.PropertyName == "DateOfBirth");
             dto.Results[dobProperty] = null;
 
@@ -1025,7 +1049,12 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
 
             var propertyMetadata = bindingContext.ModelMetadata.Properties.First(o => o.PropertyName == "PropertyWithDefaultValue");
             var validationNode = new ModelValidationNode(propertyMetadata, "foo");
-            var dtoResult = new ComplexModelDtoResult(model: null, validationNode: validationNode);
+
+            var dtoResult = new ComplexModelDtoResult(
+                model: null,
+                isModelBound: false,
+                validationNode: validationNode);
+
             var requiredValidator = bindingContext.OperationBindingContext
                                                   .ValidatorProvider
                                                   .GetValidators(propertyMetadata)
@@ -1034,7 +1063,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             var testableBinder = new TestableMutableObjectModelBinder();
 
             // Act
-            testableBinder.SetPropertyPublic(bindingContext, propertyMetadata, dtoResult, requiredValidator);
+            testableBinder.SetProperty(bindingContext, propertyMetadata, dtoResult, requiredValidator);
 
             // Assert
             var person = Assert.IsType<Person>(bindingContext.Model);
@@ -1042,6 +1071,60 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             Assert.True(bindingContext.ModelState.IsValid);
         }
 
+        [Fact]
+        public void SetProperty_PropertyIsPreinitialized_NoValue_DoesNothing()
+        {
+            // Arrange
+            var bindingContext = CreateContext(GetMetadataForObject(new Person()));
+
+            var propertyMetadata = bindingContext.ModelMetadata.Properties.Single(
+                o => o.PropertyName == "PropertyWithInitializedValue");
+            var validationNode = new ModelValidationNode(propertyMetadata, "foo");
+
+            // This value won't be used because IsModelBound = false.
+            var dtoResult = new ComplexModelDtoResult(
+                model: "bad-value",
+                isModelBound: false,
+                validationNode: validationNode);
+
+            var testableBinder = new TestableMutableObjectModelBinder();
+
+            // Act
+            testableBinder.SetProperty(bindingContext, propertyMetadata, dtoResult, requiredValidator: null);
+
+            // Assert
+            var person = Assert.IsType<Person>(bindingContext.Model);
+            Assert.Equal("preinitialized", person.PropertyWithInitializedValue);
+            Assert.True(bindingContext.ModelState.IsValid);
+        }
+
+        [Fact]
+        public void SetProperty_PropertyIsPreinitialized_WithDefaultValue_NoValue_CallsSetter()
+        {
+            // Arrange
+            var bindingContext = CreateContext(GetMetadataForObject(new Person()));
+
+            var propertyMetadata = bindingContext.ModelMetadata.Properties.Single(
+                o => o.PropertyName == "PropertyWithInitializedValueAndDefault");
+            var validationNode = new ModelValidationNode(propertyMetadata, "foo");
+
+            // This value won't be used because IsModelBound = false.
+            var dtoResult = new ComplexModelDtoResult(
+                model: "bad-value",
+                isModelBound: false,
+                validationNode: validationNode);
+
+            var testableBinder = new TestableMutableObjectModelBinder();
+
+            // Act
+            testableBinder.SetProperty(bindingContext, propertyMetadata, dtoResult, requiredValidator: null);
+
+            // Assert
+            var person = Assert.IsType<Person>(bindingContext.Model);
+            Assert.Equal("default", person.PropertyWithInitializedValueAndDefault);
+            Assert.True(bindingContext.ModelState.IsValid);
+        }
+
         [Fact]
         public void SetProperty_PropertyIsReadOnly_DoesNothing()
         {
@@ -1049,12 +1132,16 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             var bindingContext = CreateContext(GetMetadataForObject(new Person()));
             var propertyMetadata = bindingContext.ModelMetadata.Properties.Single(o => o.PropertyName == "NonUpdateableProperty");
             var validationNode = new ModelValidationNode(propertyMetadata, "foo");
-            var dtoResult = new ComplexModelDtoResult(model: null, validationNode: validationNode);
+
+            var dtoResult = new ComplexModelDtoResult(
+                model: null,
+                isModelBound: false,
+                validationNode: validationNode);
 
             var testableBinder = new TestableMutableObjectModelBinder();
 
             // Act
-            testableBinder.SetPropertyPublic(bindingContext, propertyMetadata, dtoResult, requiredValidator: null);
+            testableBinder.SetProperty(bindingContext, propertyMetadata, dtoResult, requiredValidator: null);
 
             // Assert
             // If didn't throw, success!
@@ -1069,7 +1156,12 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
 
             var propertyMetadata = bindingContext.ModelMetadata.Properties.Single(o => o.PropertyName == "DateOfBirth");
             var validationNode = new ModelValidationNode(propertyMetadata, "foo");
-            var dtoResult = new ComplexModelDtoResult(new DateTime(2001, 1, 1), validationNode);
+
+            var dtoResult = new ComplexModelDtoResult(
+                new DateTime(2001, 1, 1),
+                isModelBound: true,
+                validationNode: validationNode);
+
             var requiredValidator = bindingContext.OperationBindingContext
                                                   .ValidatorProvider
                                                   .GetValidators(propertyMetadata)
@@ -1079,7 +1171,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             var testableBinder = new TestableMutableObjectModelBinder();
 
             // Act
-            testableBinder.SetPropertyPublic(bindingContext, propertyMetadata, dtoResult, requiredValidator);
+            testableBinder.SetProperty(bindingContext, propertyMetadata, dtoResult, requiredValidator);
 
             // Assert
             validationNode.Validate(validationContext);
@@ -1100,12 +1192,15 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
 
             var propertyMetadata = bindingContext.ModelMetadata.Properties.Single(o => o.PropertyName == "DateOfDeath");
             var validationNode = new ModelValidationNode(propertyMetadata, "foo");
-            var dtoResult = new ComplexModelDtoResult(new DateTime(1800, 1, 1), validationNode);
+            var dtoResult = new ComplexModelDtoResult(
+                new DateTime(1800, 1, 1),
+                isModelBound: true,
+                validationNode: validationNode);
 
             var testableBinder = new TestableMutableObjectModelBinder();
 
             // Act
-            testableBinder.SetPropertyPublic(bindingContext, propertyMetadata, dtoResult, requiredValidator: null);
+            testableBinder.SetProperty(bindingContext, propertyMetadata, dtoResult, requiredValidator: null);
 
             // Assert
             Assert.Equal("Date of death can't be before date of birth." + Environment.NewLine
@@ -1118,16 +1213,21 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
         {
             // Arrange
             var bindingContext = CreateContext(GetMetadataForObject(new Person()));
+
             var propertyMetadata = bindingContext.ModelMetadata.Properties.Single(o => o.PropertyName == "DateOfBirth");
             var validationNode = new ModelValidationNode(propertyMetadata, "foo");
-            var dtoResult = new ComplexModelDtoResult(model: null, validationNode: validationNode);
+            var dtoResult = new ComplexModelDtoResult(
+                model: null,
+                isModelBound: true,
+                validationNode: validationNode);
+
             var requiredValidator = GetRequiredValidator(bindingContext, propertyMetadata);
             var validationContext = new ModelValidationContext(bindingContext, propertyMetadata);
 
             var testableBinder = new TestableMutableObjectModelBinder();
 
             // Act
-            testableBinder.SetPropertyPublic(bindingContext, propertyMetadata, dtoResult, requiredValidator);
+            testableBinder.SetProperty(bindingContext, propertyMetadata, dtoResult, requiredValidator);
 
             // Assert
             Assert.True(bindingContext.ModelState.IsValid);
@@ -1141,15 +1241,20 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             // Arrange
             var bindingContext = CreateContext(GetMetadataForObject(new Person()));
             bindingContext.ModelName = " foo";
+
             var propertyMetadata = bindingContext.ModelMetadata.Properties.Single(o => o.PropertyName == "ValueTypeRequired");
             var validationNode = new ModelValidationNode(propertyMetadata, "foo.ValueTypeRequired");
-            var dtoResult = new ComplexModelDtoResult(model: null, validationNode: validationNode);
+            var dtoResult = new ComplexModelDtoResult(
+                model: null,
+                isModelBound: true,
+                validationNode: validationNode);
+
             var requiredValidator = GetRequiredValidator(bindingContext, propertyMetadata);
 
             var testableBinder = new TestableMutableObjectModelBinder();
 
             // Act
-            testableBinder.SetPropertyPublic(bindingContext, propertyMetadata, dtoResult, requiredValidator);
+            testableBinder.SetProperty(bindingContext, propertyMetadata, dtoResult, requiredValidator);
 
             // Assert
             Assert.False(bindingContext.ModelState.IsValid);
@@ -1163,15 +1268,20 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             // Arrange
             var bindingContext = CreateContext(GetMetadataForObject(new ModelWhosePropertySetterThrows()));
             bindingContext.ModelName = "foo";
+
             var propertyMetadata = bindingContext.ModelMetadata.Properties.Single(o => o.PropertyName == "NameNoAttribute");
             var validationNode = new ModelValidationNode(propertyMetadata, "foo.NameNoAttribute");
-            var dtoResult = new ComplexModelDtoResult(model: null, validationNode: validationNode);
+            var dtoResult = new ComplexModelDtoResult(
+                model: null,
+                isModelBound: true,
+                validationNode: validationNode);
+
             var requiredValidator = GetRequiredValidator(bindingContext, propertyMetadata);
 
             var testableBinder = new TestableMutableObjectModelBinder();
 
             // Act
-            testableBinder.SetPropertyPublic(bindingContext, propertyMetadata, dtoResult, requiredValidator);
+            testableBinder.SetProperty(bindingContext, propertyMetadata, dtoResult, requiredValidator);
 
             // Assert
             Assert.False(bindingContext.ModelState.IsValid);
@@ -1187,15 +1297,19 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             // Arrange
             var bindingContext = CreateContext(GetMetadataForObject(new ModelWhosePropertySetterThrows()));
             bindingContext.ModelName = "foo";
+
             var propertyMetadata = bindingContext.ModelMetadata.Properties.Single(o => o.PropertyName == "Name");
             var validationNode = new ModelValidationNode(propertyMetadata, "foo.Name");
-            var dtoResult = new ComplexModelDtoResult(model: null, validationNode: validationNode);
+            var dtoResult = new ComplexModelDtoResult(model: null,
+                isModelBound: true,
+                validationNode: validationNode);
+
             var requiredValidator = GetRequiredValidator(bindingContext, propertyMetadata);
 
             var testableBinder = new TestableMutableObjectModelBinder();
 
             // Act
-            testableBinder.SetPropertyPublic(bindingContext, propertyMetadata, dtoResult, requiredValidator);
+            testableBinder.SetProperty(bindingContext, propertyMetadata, dtoResult, requiredValidator);
 
             // Assert
             Assert.False(bindingContext.ModelState.IsValid);
@@ -1290,6 +1404,11 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
 
             [DefaultValue(typeof(decimal), "123.456")]
             public decimal PropertyWithDefaultValue { get; set; }
+
+            public string PropertyWithInitializedValue { get; set; } = "preinitialized";
+
+            [DefaultValue("default")]
+            public string PropertyWithInitializedValueAndDefault { get; set; } = "preinitialized";
         }
 
         private class PersonWithBindExclusion
@@ -1497,20 +1616,12 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
                 return base.GetMetadataForProperties(bindingContext);
             }
 
-            public virtual void SetPropertyPublic(ModelBindingContext bindingContext,
+            public new void SetProperty(ModelBindingContext bindingContext,
-                                                  ModelMetadata propertyMetadata,
-                                                  ComplexModelDtoResult dtoResult,
-                                                  IModelValidator requiredValidator)
-            {
-                base.SetProperty(bindingContext, propertyMetadata, dtoResult, requiredValidator);
-            }
-
-            protected override void SetProperty(ModelBindingContext bindingContext,
                                                 ModelMetadata propertyMetadata,
                                                 ComplexModelDtoResult dtoResult,
                                                 IModelValidator requiredValidator)
             {
-                SetPropertyPublic(bindingContext, propertyMetadata, dtoResult, requiredValidator);
+                base.SetProperty(bindingContext, propertyMetadata, dtoResult, requiredValidator);
             }
         }
     }

test/WebSites/FiltersWebSite/Controllers/ActionFilterController.cs

@@ -30,12 +30,19 @@ namespace FiltersWebSite
 
         public override void OnActionExecuting(ActionExecutingContext context)
         {
-            if (context.ActionArguments["fromGlobalActionFilter"] == null)
+            object obj;
+            List<ContentResult> filters;
+
+            if (context.ActionArguments.TryGetValue("fromGlobalActionFilter", out obj))
             {
-                context.ActionArguments["fromGlobalActionFilter"] = new List<ContentResult>();
+                filters = (List<ContentResult>)obj;
             }
-            (context.ActionArguments["fromGlobalActionFilter"] as List<ContentResult>)
+            {
-                .Add(Helpers.GetContentResult(context.Result, "Controller override - OnActionExecuting"));
+                filters = new List<ContentResult>();
+                context.ActionArguments.Add("fromGlobalActionFilter", filters);
+            }
+
+            filters.Add(Helpers.GetContentResult(context.Result, "Controller override - OnActionExecuting"));
         }
 
         public override void OnActionExecuted(ActionExecutedContext context)

test/WebSites/ModelBindingWebSite/Controllers/FromHeader_BlogController.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System.ComponentModel;
 using System.ComponentModel.DataAnnotations;
 using System.Linq;
 using Microsoft.AspNet.Mvc;
@@ -21,6 +22,17 @@ namespace ModelBindingWebSite.Controllers
             };
         }
 
+        // Echo back the header value
+        [HttpGet("BindToStringParameterDefaultValue")]
+        public object BindToStringParameterDefaultValue([FromHeader] string transactionId = "default-value")
+        {
+            return new Result()
+            {
+                HeaderValue = transactionId,
+                ModelStateErrors = ModelState.Where(kvp => kvp.Value.Errors.Count > 0).Select(kvp => kvp.Key).ToArray(),
+            };
+        }
+
         // Echo back the header values
         [HttpGet("BindToStringArrayParameter")]
         public object BindToStringArrayParameter([FromHeader] string[] transactionIds)
@@ -53,6 +65,29 @@ namespace ModelBindingWebSite.Controllers
             };
         }
 
+        [HttpGet("BindToModelWithInitializedValue")]
+        public object BindToModelWithInitializedValue(BlogPostWithInitializedValue blogPost)
+        {
+            return new Result()
+            {
+                HeaderValue = blogPost.Title,
+                HeaderValues = blogPost.Tags,
+                ModelStateErrors = ModelState.Where(kvp => kvp.Value.Errors.Count > 0).Select(kvp => kvp.Key).ToArray(),
+            };
+        }
+
+        [HttpGet("BindToModelWithDefaultValue")]
+        public object BindToModelWithDefaultValue(BlogPostWithDefaultValue blogPost)
+        {
+            return new Result()
+            {
+                HeaderValue = blogPost.Title,
+                HeaderValues = blogPost.Tags,
+                ModelStateErrors = ModelState.Where(kvp => kvp.Value.Errors.Count > 0).Select(kvp => kvp.Key).ToArray(),
+            };
+        }
+
+
         private class Result
         {
             public string HeaderValue { get; set; }
@@ -73,5 +108,31 @@ namespace ModelBindingWebSite.Controllers
 
             public string Author { get; set; }
         }
+
+        public class BlogPostWithInitializedValue
+        {
+            [Required]
+            [FromHeader]
+            public string Title { get; set; } = "How to Make Soup";
+
+            [FromHeader]
+            public string[] Tags { get; set; } = new string[] { "Cooking" };
+
+            public string Author { get; set; }
+        }
+
+        public class BlogPostWithDefaultValue
+        {
+            [Required]
+            [FromHeader]
+            [DefaultValue("How to Make Soup")]
+            public string Title { get; set; }
+
+            [FromHeader]
+            [DefaultValue(new string[] { "Cooking" })]
+            public string[] Tags { get; set; }
+
+            public string Author { get; set; }
+        }
     }
 }