JoinChannel() абстрактный приватный Метод

abstract private JoinChannel ( ) : int
Результат int
        private void JoinChannelClicked(object sender, EventArgs e)
        {
            if (null != usr_engine_)
            {
                int ret = -1;
                ret = usr_engine_.Init(appId_textBox.Text, channelId_textBox.Text);
                DumpStatus("Init", ret);
                if (0 == ret)
                {
                    sdk_version.Text = "SDK Version: " + usr_engine_.GetSDKVersion();
                }

                ret = usr_engine_.JoinChannel();
                DumpStatus("joinChannel", ret);
            }
        }