not able to return Json from controller on jsonp request cross domain

Question

I am having a requirement to invoke an action returning Json data on another project from my MVC project (assuming cross origin), Using ajax. Ajax function

            var url1 = 'http://localhost:55308/Reports?type=E&code=1200?callback=?";                          


            $.ajax({                    
                url: url1,
                dataType: 'jsonp',
                contentType : 'application/json; charset=UTF-8',
                success: function (response) {
                    data = JSON.parse(response); 

                    alert('sucess');

                },
                error: function(xhr,status, error) { alert('error' + error.message);  }
            });

It is invoking the controller but returning error : Uncaught SyntaxError: Unexpected token :{"result1":"abc"}

Controller in another project is like below:

  [AllowAnonymous]        
    public ActionResult Reports(int Code, string type,string callback=null){
--- processing data--(which is working fine)
generatedPath = "df";
                    StringBuilder sb = new StringBuilder();
                    JavaScriptSerializer js = new JavaScriptSerializer();
                    sb.Append(callback + "(");
                    sb.Append(js.Serialize(generatedPath));
                    sb.Append(");");
 return Json(sb, JsonRequestBehavior.AllowGet);

}

Returning Json result. Should I encapsulate Json to JSONP data in ajax request. Stuck on this for two days and help on google is not helping. Please appreciate help. Please TIA

Edited : Added callback to jsonp request.Also dataserialized which gives me ({"df"}). Is this right?