private void uxFileChange_Click(object sender, RoutedEventArgs e)
        {
            var window = new ItemWindow();

            window.Item = selectedItem;

            if (window.ShowDialog() == true)
            {
                App.ItemRepository.Update(window.Item.ToRepositoryModel());
                selectedItem = null;
                LoadItems();
            }
        }
        private void uxFileNew_Click(object sender, RoutedEventArgs e)
        {
            var window = new ItemWindow();

            if (window.ShowDialog() == true)
            {
                var uiItemModel = window.Item;

                var repositoryItemModel = uiItemModel.ToRepositoryModel();

                App.ItemRepository.Add(repositoryItemModel);
                // OR
                //App.ItemRepository.Add(window.Item.ToRepositoryModel());

                LoadItems();
            }
        }