ASP.NET MVC3 JSON Model-binding with nested class

Question

In MVC3, is it possible to automatically bind javascript objects to models if the model has nested objects? My model looks like this:

 public class Tweet
 {
    public Tweet()
    {
         Coordinates = new Geo();
    }
    public string Id { get; set; }
    public string User { get; set; }
    public DateTime Created { get; set; }
    public string Text { get; set; }
    public Geo Coordinates { get; set; } 

}

public class Geo {

    public Geo(){}

    public Geo(double? lat, double? lng)
    {
        this.Latitude = lat;
        this.Longitude = lng;
    }

    public double? Latitude { get; set; }
    public double? Longitude { get; set; }

    public bool HasValue
    {
        get
        {
            return (Latitude != null || Longitude != null);
        }
    }
}

When I post the following JSON to my controller everything except "Coordinates" binds successfully:

{"Text":"test","Id":"testid","User":"testuser","Created":"","Coordinates":{"Latitude":57.69679752892457,"Longitude":11.982091465576104}}

This is what my controller action looks like:

    [HttpPost]
    public JsonResult ReTweet(Tweet tweet)
    {
        //do some stuff
    }

Am I missing something here or does the new auto-binding feature only support primitive objects?

Answer 1

Yes, you can bind complex json objects with ASP.NET MVC3.

Phil Haack wrote about it recently.
You've got a problem with your Geo class here.
Don't use nullable properties:

public class Geo
{

    public Geo() { }

    public Geo(double lat, double lng)
    {
        this.Latitude = lat;
        this.Longitude = lng;
    }

    public double Latitude { get; set; }
    public double Longitude { get; set; }

    public bool HasValue
    {
        get
        {
            return (Latitude != null || Longitude != null);
        }
    }
}

This is the javascript code I've use to test it:

var jsonData = { "Text": "test", "Id": "testid", "User": "testuser", "Created": "", "Coordinates": { "Latitude": 57.69679752892457, "Longitude": 11.982091465576104} };
var tweet = JSON.stringify(jsonData);
$.ajax({
    type: 'POST',
    url: 'Home/Index',
    data: tweet,
    success: function () {
        alert("Ok");
    },
    dataType: 'json',
    contentType: 'application/json; charset=utf-8'
});

UPDATE

I've tried to do some experiments with model binders and I came out with this solutions which seems to work properly with nullable types.

I've created a custom model binder:

using System;
using System.Web.Mvc;
using System.IO;
using System.Web.Script.Serialization;

public class TweetModelBinder : IModelBinder
{
    public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        var contentType = controllerContext.HttpContext.Request.ContentType;
        if (!contentType.StartsWith("application/json", StringComparison.OrdinalIgnoreCase))
            return (null);

        string bodyText;

        using (var stream = controllerContext.HttpContext.Request.InputStream)
        {
            stream.Seek(0, SeekOrigin.Begin);
            using (var reader = new StreamReader(stream))
                bodyText = reader.ReadToEnd();
        }

        if (string.IsNullOrEmpty(bodyText)) return (null);

        var tweet = new JavaScriptSerializer().Deserialize<Models.Tweet>(bodyText);

        return (tweet);
    }
}

and I've registered it for all types tweet:

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

        ModelBinders.Binders.Add(typeof(Models.Tweet), new TweetModelBinder());

        RegisterGlobalFilters(GlobalFilters.Filters);
        RegisterRoutes(RouteTable.Routes);
    }