MD5加密32大写

string userid = tbUserID.Text.Trim();
string password = tbPassword.Text.Trim();
string pwd = password + "&" + login_key;
byte[] result = Encoding.Default.GetBytes(pwd);
MD5 md5 = new MD5CryptoServiceProvider();
byte[] output = md5.ComputeHash(result);
string PWDMD5 = BitConverter.ToString(output).Replace("-", "");