Jquery跨域调用后台方法

     //前端JS
	function CallHandlerByJquery() 
	{
            var url = "http://" + window.location.hostname + "/Helper.ashx?FLAG=2&BIZINST_GUID=276259&callback=?&rand="+Math.random();
            $.ajaxSettings.async = false;
            $.getJSON(url, function (data) 
			{ 
			  alert(data.state + "|" + data.msg); 
			});
	}
		
	//后台方法
	public void ProcessRequest(HttpContext context)
        {
            string jsonResult = string.Empty;
            string callback = context.Request.QueryString["callback"];
			//业务逻辑
            jsonResult = "{state:'0',msg:'操作失败'}";
        }
        context.Response.ContentType = "application/json";
        context.Response.Write(callback + "(" + jsonResult + ")");
        context.ApplicationInstance.CompleteRequest();