//insert a new user to the database
        public void writeUserToDatabase(string groupid, string username, string password)
        {//"SET IDENTITY_INSERT dbo.Users ON" +
            sql_query = $" INSERT INTO [dbo].[Users] (Group_Id,Nickname,Password)"
                +" VALUES (@groupid,@username,@password)";
            command = new SqlCommand(sql_query, connection);

            try
            {
                connection.Open();
                int gid = int.Parse(groupid);
                SqlParameter groupid_param = new SqlParameter("@groupid", SqlDbType.Int, 4);
                SqlParameter username_param = new SqlParameter("@username", SqlDbType.Char, 8);
                SqlParameter password_param = new SqlParameter("@password", SqlDbType.Char, 64);


                groupid_param.Value = gid;
                username_param.Value = username;
                password_param.Value = password;

                command.Parameters.Add(groupid_param);
                command.Parameters.Add(username_param);
                command.Parameters.Add(password_param);

                command.ExecuteNonQuery();
                command.Dispose();
                connection.Close();
            }
            catch (Exception e)
            {
                command.Dispose();
                connection.Close();
                Logger.Instance.AddLogMessage("Error : DatabaseManager : Could not write user to database.");
                throw new Exception("Could not write user to database.");
            }
        }