public ActionResult <RemoveOrAddedOrderItemDTO> AddOrderItemByOne(long orderItemId) { try { OrderItem oi = _orderItems.GetById(orderItemId); oi.AddOne(); _orderItems.SaveChanges(); return(new RemoveOrAddedOrderItemDTO(oi.Order, oi)); } catch (ArgumentNullException) { return(NotFound(new CustomErrorDTO("Order item niet gevonden"))); } }