private void Reservation_OnClick(object sender, RoutedEventArgs e)
 {
     if (ReservationView == null || ReservationView.IsClosed)
     {
         ReservationView = new ReservationView();
         ReservationView.Show();
     }
     else
     {
         ReservationView.Focus();
     }
 }
        private void ContinueReservationExecute(object obj)
        {
            ReservationView view = new ReservationView()
            {
                DataContext = new ReservationViewModel(Reservation)
            };

            if (ChooseShowingView.GetInstance() != null)
            {
                ChooseShowingView.GetInstance().Close();
            }
            view.Show();
        }