public MainWindow() { InitializeComponent(); cbxUnionUser.ItemsSource = unionHandler.GetAllUnions(); dgActivitiesUser.ItemsSource = activityHandler.GetAllActivities(); cbxAdmin.ItemsSource = adminHandler.GetAllAdmins(); dgReservationsAdmin.ItemsSource = reservationHandler.GetAlllReservation(); dgBookingOverviewAdmin.ItemsSource = bookingHandler.GetAllBookings(); dgReservationsUser.ItemsSource = reservationHandler.GetAlllReservation(); }