asp.net jquery ajax 跨域调用

js:

        jQuery(document).ready(function(){
                $.ajax({
                    type : "GET",
                    url : "http://service.test.com/t1.ashx?callback=?",
                    dataType : "jsonp",
                   jsonp: "callback",
                    success : function(json){
                        $('#feeds').html(json.msg);
                        return true;
                    }
                });
            });

    <div id="feeds">   </div>

t1.ashx

         public void ProcessRequest(HttpContext context)
2         {
3             context.Response.ContentType = "text/html";
4             string callback = context.Request.Params["callback"];
5             context.Response.Write(callback + "({\"msg\":\"jquery test message!\"})");
6         }