private async void save(object sender, EventArgs e) { if (fineCheckbox.Checked) { Fine fine = new Fine(); await saveFine(fine, reservation).ContinueWith(async task => { int fineId = (int)task.Result; if (fineId > 0) { reservation.fineId = fineId; reservation._checked = true; await DatabaseService.updateReservation(reservation); } else { MessageBox.Show("Przepraszamy, nie udało się zapisać opłaty."); } }); } if (!efficientCheckbox.Checked) { Car car = new Car(); car.registrationNumber = reservation.registrationNumber; car.carEfficiency = efficientCheckbox.Checked; await DatabaseService.updateCar(car); } showParent(); }