public DeliveryViewModel ChangeRecepient(int deliveryId, string newRecepient) { var delivery = _deliveryRepository.GetById(deliveryId); if (delivery == null) { throw new InvalidOperationException("Delivery doesn't exist"); } if (newRecepient == null) { throw new ArgumentNullException(nameof(newRecepient), "Recepient is null"); } var user = GetUser(newRecepient); if (user == null) { throw new InvalidOperationException("User doesn't exist"); } return(_deliveryRepository.ChangeRecepient(delivery, newRecepient).ToDeliveryViewModel()); }