为什么没有在我的mvc项目中序列化此属性？

Question

The ultimate goal is to serialize an abstract type from my View to be consumed by my Controller .

My abstract type has an enum property whose names correspond to the names of the concrete derived types; this is how I will determine which concrete type to select. The value of this enum is set in the constructor of the abstract type via reflection:

[JsonConverter(typeof(BlockJsonConverter)]
public abstract class Block{

   [NotMapped, JsonProperty]
   public BlockType BlockType {get; set;}
   public string Name {get;set:}
   public int Height{get;set;}
   public int Width {get;set;}
   public int Depth {get;set;}

   protected Block(){
      BlockType = Enum.TryParse(GetType().Name, out BlockType blocktype)
             ?? blocktype : BlockType.Unknown
   }
}

public enum BlockType {
   Long, Short, Tall, Unknown
}

public class Long    : Block { /*...*/ }
public class Short   : Block { /*...*/ }
public class Tall    : Block { /*...*/ }
public class Unknown : Block { /*...*/ }

The Block class is used by Entity Framework but the BlockType property is not stored in the database, so the BlockType property is marked with the [NotMapped] attribute; however, since I want the property to be round-tripped from the View to the Controller, I have marked it with the [JsonProperty] attribute.

I have created a TestModelBinder to handle the deserialization from the View to the Controller:

public class TestModelBinder : DefaultModelBinder
{
    protected override object CreateModel(ControllerContext controllerContext, 
       ModelBindingContext bindingContext, Type modelType)
    {
        return base.CreateModel(controllerContext, bindingContext,
            GetModelType(controllerContext, bindingContext, modelType));
    }

    protected override ICustomTypeDescriptor GetTypeDescriptor(
      ControllerContext controllerContext,ModelBindingContext bindingContext)
    {
        var modelType = GetModelType(controllerContext, bindingContext, bindingContext.ModelType);
        return new AssociatedMetadataTypeTypeDescriptionProvider(modelType)
                      .GetTypeDescriptor(modelType);
    }

    private static Type GetModelType(ControllerContext controllerContext, ModelBindingContext bindingContext,
        Type modelType)
    {
        if (modelType.Name == "Block")
        {
• breakpoint
           // get the value from bindingContext for BlockType
           // and return the concrete type based on that
        }
        return modelType;
    }
}

When I hit that breakpoint above, the bindingContext does not have a BlockType in its ValueProvider.FormValueProvider for my BlockType property - but the Name , Height , Width and Depth properties are listed as expected.

They're all listed the same way in the EditorTemplate:

@model Block
<div class="form-row">
    <div class="col">
        @Html.BootstrapEditorGroupFor(m => m.Name)
    </div>        
    <div class="col">
        @Html.BootstrapEditorGroupFor(m => m.BlockType)
    </div>
</div>
<div class="form-row">
    <div class="col">
        @Html.BootstrapEditorGroupFor(m => m.Height)
    </div>
    <div class="col">
        @Html.BootstrapEditorGroupFor(m => m.Width)
    </div>
    <div class="col">
        @Html.BootstrapEditorGroupFor(m => m.Depth)
    </div>
</div>

... and the BootstrapEditorGroupFor helper just generates the usual label, editor based on type (enum, string, etc), and validation message. The EditorTemplate for Enums is below:

@model Enum

@{
    var type = Nullable.GetUnderlyingType(ViewData.ModelMetadata.ModelType) 
               ?? ViewData.ModelMetadata.ModelType;
}

<div class="form-group">
    <select class="form-control">
        @if (ViewData.ModelMetadata.IsNullableValueType)
        {
            <option selected="@ReferenceEquals(Model, null)">Not Specified</option>
        }
        @foreach (var value in Enum.GetValues(type))
        {
            <option selected="@value.Equals(Model)">@value</option>
        }
    </select>
</div>

Answer 1

Your select element doesn't seems to be rendering the name of the element. Without the name attribute the data will not get matched to the appropriate property in you model. You can double check it by just editing the HTML in your browser and adding an attribute name="BlockType" to your select input and try posting the form to see if it works.