private void FrmGroupChat_FormClosed(object sender, FormClosedEventArgs e) { if (_roomJid != null) { mm.ExitRoom(_roomJid, _nickname); // Remove the Message Callback in the MessageFilter _xmppClient.MessageFilter.Remove(_roomJid); // Remove the Presence Callback in the MessageFilter _xmppClient.PresenceFilter.Remove(_roomJid); } }