private void CarExitsCarPark(object sender, EventArgs e) { carPark.CarExitedCarPar(); exitSensor.CarLeftSensor(); btnCarExitsCarPark.Visible = false; btnCarArrivesAtEntrance.Visible = !btnCarEntersCarPark.Visible && !btnDriverPressesForTicket.Visible; btnCarArrivesAtExit.Visible = !carPark.IsEmpty(); UpdateDisplay(); }