string HmacMD5(string source, string key)        {            HMACMD5 hmacmd = new HMACMD5(Encoding.Default.GetBytes(key));            byte[] inArray = hmacmd.ComputeHash(Encoding.Default.GetBytes(source));            StringBuilder sb = new StringBuilder();             for (int i = 0; i < inArray.Length; i++)            {                sb.Append(inArray[i].ToString("X2"));            }                        hmacmd.Clear();                        return sb.ToString();        }