Ajax跨域请求

$.ajax({
    dataType: "jsonp",
    data: { "ajaxMethod": "getusergamesign", "cookieid": cookieid },
    jsonp: "jsonp_callback",  //服务器端接收，用于function名，随便定义
    url: ‘http://b.test.com/Ajax/UserGameSign.ashx‘,  //请求不同域名的地址
    success: _callBack,   //也可以写function(result) {...};
    error: function() {
        alert(‘服务器内部错误！‘);
    }
});

var _callBack = function(result) {   //result为返回的值：{"code":0,"msg":"IB"}  
if (result != null) {
    if (result.code == 0) {
        alert(result.msg);
    }
}
};

type : "get", //或post
async:false, //我试了没起到同步的效果

 public class UserGameSign : BaseCommon, IHttpHandler
    {
        public void ProcessRequest(HttpContext context)
        {
                try
                {
                    if (!string.IsNullOrEmpty(context.Request["ajaxMethod"]))
                    {
                        string responseText = "";
                        context.Response.ContentType = "text/plain";
                        string ajaxMethod = context.Request["ajaxMethod"].ToLower();
                        switch (ajaxMethod)
                        {
                            case "getusergamesign":
                                responseText = this.GetUserGameSign(context);
                                break;
                            default:
                                break;
                        }
                        context.Response.Write(responseText); //返回的结果：{"code":0,"msg":"IB"}
                        context.Response.End();
                    }
                }
                catch (Exception ex) //解决此错误：Thread was being aborted. 问题详解>>
                {
                    if (!(ex is System.Threading.ThreadAbortException))
                    {
                        context.Response.Write(ex.Message);
                        context.Response.End();
                    }
                }
        }

        /// <summary>
        /// 获取用户标签
        /// </summary>
        /// <param name="context"></param>
        /// <returns></returns>
        public string GetUserGameSign(HttpContext context)
        {
            string cookieIdstr = context.Request["cookieid"];
            string strFormat = "{{\"code\":{0},\"msg\":\"{1}\"}}";

            //判断是否是jsonp方式请求 
            string jsonp = string.Empty;
            if (!string.IsNullOrEmpty(HttpContext.Current.Request["jsonp_callback"]))
            {
                jsonp = context.Request["jsonp_callback"];
                context.Response.ContentType = "text/javascript";
            }

            User user = new User();
            string userProperty = user.GetUseProperty(cookieId);
            if (!string.IsNullOrEmpty(userProperty))
            {
                if (string.IsNullOrEmpty(jsonp))
                {
                    return string.Format(strFormat, 0, userProperty); //正常形式返回
                }
                else
                {
                    //jsonp类型的返回 格式：jsonp({"code":0,"msg":"IB"}) 作为前端ajax回调函数的参数
                    return jsonp + "(" + string.Format(strFormat, 0, userProperty) + ")"; 
                }
            }
            else
            {
                return string.Format(strFormat, -1, "失败");
            }
        }

    }