public bool CheckUserData(string account, string password)
        {
            try
            {
                string       sql = "SELECT 1 FROM user WHERE account = @account AND password = @password;";
                MySqlCommand cmd = db.MySqlCommand(sql);
                cmd.Parameters.Add("@account", MySqlDbType.VarChar).Value  = account;
                cmd.Parameters.Add("@password", MySqlDbType.VarChar).Value = password;

                db.Connect();

                using (MySqlDataReader reader = cmd.ExecuteReader())
                {
                    if (reader.Read())
                    {
                        return(true);
                    }
                }
                return(false);
            }
            catch (Exception ex)
            {
                string error = ex.ToString();
                return(false);
            }
            finally
            {
                db.Disconnect();
            }
        }