public static string encrypt(string str)
        {
            string cl = str;
            string pwd = "";
            MD5 md5 = MD5.Create();
            byte[] s = md5.ComputeHash(Encoding.UTF8.GetBytes(cl));
            for (int i = 0; i < s.Length; i++)
            {
                pwd = pwd + s[i].ToString("X");
            }
            return pwd;
        }
        #endregion
    }

 pwd = pwd + s[i].ToString("X2");