void ListenOrStopListen() { if ((tv_Sessions.SelectedNode != null) && (tv_Sessions.SelectedNode.Tag != null)) { var session = (ISession)tv_Sessions.SelectedNode.Tag; if (session == null) { return; } if (listened.Contains(session)) { presenter.StopListening(session); btn_Listen.Text = Constants.LISTEN; tv_Sessions.SelectedNode.BackColor = joined.Contains(session) ? Constants.JOINED_COLOR : tv_Sessions.BackColor; } else { presenter.Listen(session); btn_Listen.Text = Constants.STOP_LISTENING; tv_Sessions.SelectedNode.BackColor = Constants.LISTENING_COLOR; } } }