HttpWebRequest 请求带返回值url

                     HttpWebRequest hr = (HttpWebRequest)WebRequest.Create(url);
                hr.UserAgent = "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1)";
                hr.Method = "GET";
                hr.Timeout = 30 * 60 * 1000;
                WebResponse hs = hr.GetResponse();
                Stream sr = hs.GetResponseStream();
                StreamReader ser = new StreamReader(sr, Encoding.Default);
                res = ser.ReadToEnd();
                sr.Close();
                ser.Close();