private void BTN_modifierWagon_Click(object sender, RoutedEventArgs e)
 {
     if (DG_listewagon.SelectedItem == null)
     {
         MessageBox.Show("aucun wagon selectionné");
         return;
     }
     CWagon objWagon = (CWagon)DG_listewagon.SelectedItem;
     fenetreWagon wag = new fenetreWagon(gestionTrain, objWagon);
 }
 // boutons wagon
 private void BTN_ajoutWagon_Click(object sender, RoutedEventArgs e)
 {
     fenetreWagon wag = new fenetreWagon(gestionTrain);
 }