private async void saveReservation(Car car) { await DatabaseService.updateReservationOnEdit(reservation, car).ContinueWith(task => { bool result = task.Result; if (result) { MessageBox.Show("Zapisano"); if (InvokeRequired) { Invoke(new Action(() => { refreshDatabase(); Hide(); })); } else { Hide(); } } else { MessageBox.Show("Nie zapisano"); } }); }