ASP.NET MVC 3 - where is my JsonValueProvider?

I am trying to send JSON to an Action method:

[HttpPost]
public virtual ActionResult KoUpdateAccount(CostCentreDTOX cc)
{
    if (cc.NameCC == null)
    {
        return Json(new { message = "Im null" });
    }
    else
    {
        string s = cc.NameCC;
        return Json(new { message = s });
    }
}

Where CostCentreDTOX is defined as:

[Serializable]
public class CostCentreDTOX
{
    public int CostCentreId { get; set; }
    public int IdTr开发者_JAVA技巧ansactionType { get; set; }
    public string NameCC { get; set; }
}

The Json is created by doing (I am using Knockoutjs):

var json = ko.toJSON(this.costCentres()[0]);

This produces the following string (which is what I want):

"{"CostCentreId":5,"IdTransactionType":2,"NameCC":"Impuestos"}"

The method that sends everything to the server is:

this.save = function() { 
    var json = ko.toJSON(this.costCentres()[0]);
    api.postCud({
        url: "/admin/Accounts/KoUpdateAccount/",
        dataType: 'JSON',
        data: json,
        type: "post",
        contentType: "application/json; charset=utf-8",
        success: function(result) { alert(result.message) }
    });
}

Where this.costCentre()[0] is an object defined as follows:

function costCentre(CostCentreId, IdTransactionType, NameCC) {

    this.CostCentreId      = ko.observable(CostCentreId); 
    this.IdTransactionType = ko.observable(IdTransactionType); 
    this.NameCC            = ko.observable(NameCC);
}

However, the Action parameter cc just gets instantiated to its default values, as if the JsonValueProvider wasn't registered. But I am using ASP.NET MVC 3, so it should be there, right? Just there.

EDIT:

I have tried adding the following to the Global.asax file:

protected void Application_Start()
        {
            AreaRegistration.RegisterAllAreas();

            RegisterGlobalFilters(GlobalFilters.Filters);
            RegisterRoutes(RouteTable.Routes);
            ValueProviderFactories.Factories.Add(new JsonValueProviderFactory());
        }

But still, cc gets instantiated with default values.

any suggestions??

Is the api.postCud is that doing something exotic that could problems when it executes the post? Have you tried with $.ajax() instead just to see it that works?

As @Major Byte suspected, there was an issue with they way the ajax call was being made. This is done via a method, api.postCud, defined on an api.

The method is just a wrapper around $.ajax (see Eric Sowell's MvcConf2 video: Evolving Practices in Using jQuery and Ajax in ASP.NET MVC Applications). The problem being that it merges the options for the $.ajax call using $.extend() and I had included no provision for the dataType option.

So MVC was unaware that JSON was being posted, and therefore the model binding wasn't working.

This is what happens when I get 2 hours sleep...