京东WebService调用 求助~~~~~

请教各位  为什么这样调用获取不到数据

            string venderSign = "";      //签名
            string tradeno = DateTime.Now.Ticks.ToString();//流水号
            long venderID = 20388; //商家ID
            string secretcode = "08D434A563ABE0712B8DCD15B762D33C";  //商家key
            venderSign = MD5.Encrypt(secretcode + venderID.ToString() + tradeno + secretcode,32);   //MD5加密
            string startDate="2011-03-01 00:00:01";  //开始日期
            string endDate="2011-03-28 00:00:01";   //终止日期
            string field = "venderId,orderState";

            JD.OrderSearchServiceImplService s = new jingdong.JD.OrderSearchServiceImplService();
            JD.apiOrderQueryDetail detail = s.searchOrderInfo(venderSign, tradeno, venderID, startDate, endDate, "ALL", "100", "20", field);
            string dfds = detail.apiResult.chineseErrCode;
            bool t = detail.apiResult.success;    //这里返回的为true

            int total = detail.orderTotal;       //为什么这儿没有订单信息 返回的总订单数为0



请问各位，是什么原因导致的？？？