private void AddCar(object sender, RoutedEventArgs e)
        {
            decimal.TryParse(CarPrice.Text, out decimal price);
            string name = CarName.Text;

            if (CarEngine.SelectedIndex >= 0 && CarGearbox.SelectedIndex >= 0 && CarInterior.SelectedIndex >= 0 && CarExterior.SelectedIndex >= 0 && price >= 0)
            {
                EngineUI   engineUI   = CarEngine.SelectedItem as EngineUI;
                GearboxUI  gearboxUI  = CarGearbox.SelectedItem as GearboxUI;
                InteriorUI interiorUI = CarInterior.SelectedItem as InteriorUI;
                ExteriorUI exteriorUI = CarExterior.SelectedItem as ExteriorUI;
                CarUI      carUI      = new CarUI()
                {
                    Engine = engineUI, Exterior = exteriorUI, Gearbox = gearboxUI, Interior = interiorUI, Name = name, Price = price, Status = "Not Sold"
                };
                Methods.AddCar(carUI);
            }
        }