private void RadioButtonPorsche_Checked(object sender, RoutedEventArgs e)
        {
            ICarFactory carFactory = new PorscheFactory();

            carDealer = new CarDealer(carFactory);
        }
        private void RadioButtonVolkswagen_Checked(object sender, RoutedEventArgs e)
        {
            ICarFactory carFactory = new VolkswagenFactory();

            carDealer = new CarDealer(carFactory);
        }