public void AfficherVol()
{
ListeVols = new ObservableCollection <Vol>();
ListeVols = DAL_Vol.SelectVols();
this.grid.ItemsSource = ListeVols;
this.trajet.ItemsSource = DAL_Trajet.SelectStrTrajets();
this.avion.ItemsSource = DAL_Avion.SelectMatriculeAvions();
this.Trajet.ItemsSource = DAL_Trajet.SelectStrTrajets();
this.Trajet.SelectedValue = DAL_Trajet.SelectStrTrajets().First();
this.Avion.ItemsSource = DAL_Avion.SelectMatriculeAvions();
this.Avion.SelectedValue = DAL_Avion.SelectMatriculeAvions().First();
}