protected string UrlEncode(string url)
        ...{
            byte[] bs = Encoding.GetEncoding("GB2312").GetBytes(url);
            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < bs.Length; i++)
            ...{
                if (bs[i] < 128)
                    sb.Append((char)bs[i]);
                else
                ...{
                    sb.Append("%" + bs[i++].ToString("x").PadLeft(2, '0'));
                    sb.Append("%" + bs[i].ToString("x").PadLeft(2, '0'));
                }
            }
            return sb.ToString();
        }