private void CreateReservation_Click(object sender, RoutedEventArgs e)
 {
     CreateReservation newWindow = new CreateReservation();
     newWindow.ShowDialog();
 }
        private void UpdateReservation_Click(object sender, RoutedEventArgs e)
        {
            IReservation reservation = (IReservation)reservationListBox.SelectedItem;

            CreateReservation openReservation = new CreateReservation(reservation);
            openReservation.ShowDialog();
        }