public void Undo()
        {
            switch (_previousSpeed)
            {
            case CeilingFanSpeed.High:
                _ceilingFan.High();
                break;

            case CeilingFanSpeed.Medium:
                _ceilingFan.Medium();
                break;

            case CeilingFanSpeed.Low:
                _ceilingFan.Low();
                break;

            case CeilingFanSpeed.Off:
                _ceilingFan.Off();
                break;
            }
        }
 public void Execute()
 {
     _previousSpeed = _ceilingFan.Speed;
     _ceilingFan.Off();
 }