public string Undo()
{
switch (_prevSpeed)
{
case Fan.High:
return(_fan.SetHigh());
case Fan.Medium:
return(_fan.SetMedium());
case Fan.Low:
return(_fan.SetLow());
case Fan.Off:
return(_fan.SetOff());
default:
return("fan set speed error");
}
}
public string Execute()
{
_prevSpeed = _fan.Speed;
return(_fan.SetHigh());
}