MVC3 RC2 JSON Post Binding not working correctly

Question

I've seen other posts on this subject and have fiddled with variations but still cannot not get the JSON model binding to work correctly.

I have the following in my global.asax.cs Application_Start method:

ValueProviderFactories.Factories.Add(new JsonValueProviderFactory());

The post back data looks like this:

{"UserName":"Mike","Password":"password","Persist":true}

My PoCo:

public class UserLoginViewModel {
    public string UserName { get; set; }
    public string Password { get; set; }
    public bool Persist { get; set; }
}

The controller method fires properly but has default UserLoginViewModel object with UserName = null, Password = null, and Persist = false; the signature looks like this:

[HttpPost]
public ActionResult Logon(UserLoginViewModel model) {
    if (ModelState.IsValid) { 
    ...

Answer 1

The problem is on the client side! I didn't have the contentType set.

$.ajax({
    url: location.href, 
    type: "POST",
    data: ko.toJSON(this),
    datatype: "json",
    **contentType: "application/json charset=utf-8",**
    success: function (data) { alert("success"); }, 
    error: function (data) { alert("error"); }
});