class Client
    {
        public event EventHandler<ConnectedEventArgs> ClientConneted;

        protected virtual void OnClientConnected(ConnectedEventArgs e)
        {
            if (ClientConneted != null) ClientConneted(this, e);
        }

        public Client()
        {
        }

        public void Connect()
        {
            //Procédure de connexion ....
            // Si connecté :

            //Déclenchement de l'évenement
            OnClientConnected(new ConnectedEventArgs("Connexion OK !",14));
        }
    }

    //Classe de l'argument de l'evement
    public class ConnectedEventArgs : EventArgs
    {
        internal string m_msg;   //Un parametre quelconque passé
        internal int m_val;

        public ConnectedEventArgs(string msg, int val)
        {
            m_msg = msg;
            m_val = val;
        }
    }