ASP.NET MVC 3 JSONP: Does this work with JsonValueProviderFactory?

Question

Phil Haack has an excellent blog post on how to use JSON, data binding, and data validation.

Enter the browser\'s \"same origin policy security restriction.\" and JS

Answer 1

As far as receiving a JSON string and binding it to a model is concerned the JsonValueProviderFactory does this job out of the box in ASP.NET MVC 3. But there is nothing built-in for outputting JSONP. You could write a custom JsonpResult:

public class JsonpResult : JsonResult
{
    public override void ExecuteResult(ControllerContext context)
    {
        if (context == null)
        {
            throw new ArgumentNullException("context");
        }
        var request = context.HttpContext.Request;
        var response = context.HttpContext.Response;
        string jsoncallback = (context.RouteData.Values["jsoncallback"] as string) ?? request["jsoncallback"];
        if (!string.IsNullOrEmpty(jsoncallback))
        {
            if (string.IsNullOrEmpty(base.ContentType))
            {
                base.ContentType = "application/x-javascript";
            }
            response.Write(string.Format("{0}(", jsoncallback));
        }
        base.ExecuteResult(context);
        if (!string.IsNullOrEmpty(jsoncallback))
        {
            response.Write(")");
        }
    }
}

And then in your controller action:

public ActionResult Foo()
{
    return new JsonpResult
    {
        Data = new { Prop1 = "value1", Prop2 = "value2" },
        JsonRequestBehavior = JsonRequestBehavior.AllowGet
    };
}

which could be consumed from another domain with $.getJSON():

$.getJSON('http://domain.com/home/foo?jsoncallback=?', function(data) {
    alert(data.Prop1);
});