public void RemoveAppointment(int appointmentId) { lock (_lockingObject) { _persistable.RemoveAppointment(appointmentId); Appointment appointment = _appointments.Find(appointment1 => appointment1.Id == appointmentId); _updateAppointmentNotification.AppointmentDeletedNotification(appointment); _appointments.Remove(appointment); } AppointmentsChangedEventHandler?.Invoke(appointmentId, EventArgs.Empty); }