public virtual void OnSpeedChanged(int oldSpeed, int newSpeed)
        {
            SpeedChangedEventArgs e = new SpeedChangedEventArgs();

            e.OldSpeed = oldSpeed;
            e.NewSpeed = newSpeed;

            if (_speedChangedEventHandler != null)
            {
                _speedChangedEventHandler(this, e);
            }
        }
 static void CarSpeedChanged(object source, SpeedChangedEventArgs e)
 {
     Console.WriteLine("Car speed changed from {0} to {1}",
                       e.OldSpeed, e.NewSpeed);
 }