Why isn't this nested model being deserialized as I expect?

Question

For a minute please ignore the travesty that is this complicated model, and assume you are stuck with it :)

public class Foo
{
   public FooList Foos{get;set;}
}

public class FooList
{
    public object SomeBar {get; set;}
}

public class Bar
{
    public string Name {get;set;}
}

public class AnotherBar
{
    public bool IsCrazy{get;set;}
}

So we will give the Action a Foo and the foo will have a FooList Which contians either Bar or AnotherBar. What SomeBar contains doesn't really matter..it is an object of a few KNOWN types, but we don't know which one...oh and they don't inherit from a common ancestor.

Ok, so when you post json to an action that takes a Foo. the Foo object will be deserialized, but FooList is null. If I create a custom ModelBinder, manually read in the stream and tell JsonConvert to deserialize it. everything works

From what I understand MVC4 uses JsonConvert under the covers. What is the difference here? Why would the built-in deserialization not work and me explicitly using JsonConvert does?

I am probably going to have to bounty this, and I plan on putting as much as I can (500?)

ps. I am not asking for a work around. I really just want to know what is going on to cause the behavior.

Now for the code:

//some sample JSON: {"Foos":{"SomeBar":{"Name":"Insanity"}}}


public ActionResult Test(Foo foo)
{
     //Foo.FooList is null
    return new EmptyResult();
}

public ActionResult BinderTest([ModelBinder(typeof(FooModelBinder))] Foo foo)
{ 
    //Everything is as it should be
    return new EmptyResult();
}

public class FooModelBinder : IModelBinder
{
    public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        var request = controllerContext.HttpContext.Request;
        request.InputStream.Seek(0, SeekOrigin.Begin);

        var jsonString = new StreamReader(request.InputStream).ReadToEnd();

        Foo foo = JsonConvert.DeserializeObject<Foo>(jsonString);

        return foo;
    }
}

And some client code

$(function () {
        $('#button1').click(function () {
            var data = '{"Foos":{"SomeBar":{"Name":"Insanity"}}}';
            $.post('/home/bindertest', data);
        });

        $('#button2').click(function () {
            var data = '{"Foos":{"SomeBar":{"Name":"Insanity"}}}';
            $.post('/home/test', data);
        });
    });

Have you checked the `ModelState` collection for simple binding errors? — asawyer, Jul 30 '13 at 17:12
I have encoutered the exact same issue.. seen here. http://stackoverflow.com/questions/17309076/can-i-use-json-net-de-serialization-by-default-with-asp-net-web-api-and-mvc-3 if you just a use JSON convert it works. We ended up having to write a proxy class so not my method looks like this. `MyActionResultMethod([JsonNet] DTO.MyDTO) { ` Fun times... — recneps, Jul 30 '13 at 17:28
@recneps If you read my question I post that using JsonConvet works. I am trying to find out why :) — , Jul 30 '13 at 17:31
It most likely boils down to what the post data looks like. Fire up Fiddler2 and take a look at the raw post. Most likely the problem is incorrect formatting there. — asawyer, Jul 30 '13 at 18:01
@asawyer I have done that. The data is the exact same. Nothing has changed between the two except in one I use a model binder to manually deserialize the data — , Jul 30 '13 at 18:29
Fire up a basic MVC4 site and use the code I provided above. You can easily test it — , Jul 30 '13 at 18:30

score 2 · Accepted Answer · edited May 23 '17 at 10:09

2

The default serializer for Web API controllers (classes inheriting from ApiController) in MVC 4 is Json.Net. However, I believe the default serializer for standard MVC 4 controllers (classes inheriting from Controller) is still the JavaScriptSerializer (for backward compatibility reasons). See this question. So that could very well explain the difference in behavior.

edited May 23 '17 at 10:09

Community

1
1

answered Jul 30 '13 at 18:36

Brian Rogers

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ahhh that makes perfect sense! And here I was under the impression MVC4 as a whole was using Json.net. Thanks! – Jul 30 '13 at 19:08

Why isn't this nested model being deserialized as I expect?

1 Answers1