public IActionResult CreateNewOrder(int UserId, LineItems lineItemToAdd) { var findUser = _userRepository.GetUserById(UserId); if (findUser == null) { return(NotFound("This user could not be found.")); } var hasCart = _repository.FindOpenCarts(UserId); var totalCost = lineItemToAdd.Price * lineItemToAdd.Quantity; OrderCart cart; if (hasCart != null) { cart = _repository.AddToExistingCart(hasCart.InvoiceId, totalCost); } else { cart = _repository.StartNewOrder(UserId, totalCost); } lineItemToAdd.InvoiceId = cart.InvoiceId; var newLineItem = _repository.AddLineItem(lineItemToAdd); if (newLineItem == null) { return(NotFound("There was an error adding this item to your cart. Please try again.")); } return(Created("", cart)); }