public InventoryNavigationItemViewModel(IRegionManager regionManager, IEventAggregator eventAggregator)
        {
            this.RegionManager = regionManager;

            InventoryNavigatedEvent inventoryNavigatedEvent = eventAggregator.GetEvent <InventoryNavigatedEvent>();

            inventoryNavigatedEvent.Subscribe(this.SetButtonText);
        }
        public InventoryViewModel(
            IRegionManager regionManager, 
            IEventAggregator eventAggregator,
            IItemRepository itemRepository,
            ICategoryRepository categoryRepository): base(regionManager) {

            _itemRepository = itemRepository;
            _categoryRepository = categoryRepository;

            _inventoryNavigatedEvent = eventAggregator.GetEvent<InventoryNavigatedEvent>();
            regionManager.Regions[Constants.MainContentRegion].NavigationService.Navigated += NavigationService_Navigated;
        }