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();         }