gistfile1.cs

    public class InventoryController : ApiController
    {
        private readonly IInventoryManagementService _inventoryManagementService;
        private readonly IUnitOfWork _unitOfWork;

        public InventoryController(IUnitOfWork unitOfWork)
        {
            _unitOfWork = unitOfWork; //access services
            _inventoryManagementService = _unitOfWork.Get<IInventoryManagementService>();
        }

        //thin controller action
        public ActionResult UpdateItem(InventoryItemViewModel item)
        {
            InventoryItem domainItem = item.ToDomainObject();
            _inventoryManagementService.AddOrUpdateItem(domainItem);

            return View();
        }
       
    }

    public class InventoryManagementService : IInventoryManagementService
    {
        IInventoryRepository _inventoryRepository;
        IUserRepository _userRepository;

        //inject any repositories that are require or provide repositories via a UnitOfWork
        public InventoryManagementService(IInventoryRepository inventoryRepository, IUserRepository userRepository)
        {
            _inventoryRepository = inventoryRepository;
            _userRepository = userRepository;
        }

        // Business logic is in the service not the controller action
        public void AddOrUpdateItem(InventoryItem item)
        {            
            var itemExists = _inventoryRepository.GetById(item.Id);

            if (itemExists)
            {
                _inventoryRepository.Update(item);
            }
            else
            {
                _inventoryRepository.Add(item);
            }
        }

    }