Question

Been doing some playing call my service which is on a different domain using jQuery. The call to the service is successfully made (my debug point gets tripped), and the correct response is returned (I sniff the traffic).

My problem is mainly that the success and failure callbacks don’t get fired. I have read some other posts on SO that indicate the error event is not fired when using JSONP. Is that the case with the success event (perhaps because it is assumed that I am providing my own callback function), as well, or is there a way to fire my success callback. Thanks in advance.

$.ajax({
  type: "GET",
  url: urlOnDiffDomain,
  async: false,
  cache: false,
  dataType: 'jsonp',
  data: {},
  success: function(data, textStatus) {
    alert('success...');
  },
  error: function(xhr, ajaxOptions, thrownError) {
   alert('failed....');
  }
}); 

Answer 1

Alright. In case anyone needs to know in the future…In hindsight, the solution probably should have been more obvious than it was, but you need to have the web-response write directly to the response stream. Simply returning a string of JSON doesn’t do it, you need to someone construct it and stream it back. The code in my original post will work fine if you do indeed do that.

Example of service code:

public void DoWork()
{
  //it will work without this, but just to be safe
  HttpContext.Current.Response.ContentType = "application/json"; 
  string qs = HttpContext.Current.Request.QueryString["callback"];
  HttpContext.Current.Response.Write(qs + "( [{ \"x\": 10, \"y\": 15}] )");
}

Just for the sake of being explicit, this is the client-side code.

function localDemo(){
  $.getJSON("http://someOtherDomain.com/Service1.svc/DoWork?callback=?",
    function(data){
      $.each(data, function(i,item){            
        alert(item.x);
      });
  });
}

If there is a better way to do this, I am all ears. For everyone else, I know there is some concept of native support in WCF 4.0 for JSONP. Also, you may want to do a little checking for security purposes – though I have not investigated much.