private async void AppBarButton_Click_ReloadBookShelf(object sender, RoutedEventArgs e)
        {
            var cbs = (await GetCurrentBookShelf());

            if (cbs == null)
            {
                return;
            }
            var item = await Books.BookManager.StorageItemGet(cbs.GetFirstAccessToken());

            var storage = await BookShelfStorage.GetBookShelves();

            var target = storage[(await GetActualCurrentIndex())];

            if (item is Windows.Storage.StorageFolder)
            {
                CurrentOperationCount++;
                var result = BookShelfStorage.GetFlatBookShelf(await BookShelfStorage.GetFromStorageFolder(item as Windows.Storage.StorageFolder));
                result.Secret = target.Secret;
                var CurrentIndex = storage.IndexOf(target);
                if (CurrentIndex >= 0)
                {
                    storage[CurrentIndex] = result;
                }
                CurrentOperationCount--;
                Refresh();
            }
        }
        private async void AppBarButton_Click_AddLocalDirectory(object sender, RoutedEventArgs e)
        {
            var picker = new Windows.Storage.Pickers.FolderPicker();

            foreach (var ext in Books.BookManager.AvailableExtensionsArchive)
            {
                picker.FileTypeFilter.Add(ext);
            }
            var folder = await picker.PickSingleFolderAsync();

            if (folder != null)
            {
                var rl = new Windows.ApplicationModel.Resources.ResourceLoader();

                var dialog = new Windows.UI.Popups.MessageDialog(rl.GetString("LoadingFolder/Started/Message"), rl.GetString("LoadingFolder/Title"));
                await dialog.ShowAsync();

                var storage = await BookShelfStorage.GetBookShelves();

                CurrentOperationCount++;
                storage.Add(BookShelfStorage.GetFlatBookShelf(await BookShelfStorage.GetFromStorageFolder(folder)));
                CurrentOperationCount--;
                Refresh();
                if (BookShelfList.Items != null)
                {
                    BookShelfList.SelectedIndex = BookShelfList.Items.Count - 1;
                }

                dialog = new Windows.UI.Popups.MessageDialog(rl.GetString("LoadingFolder/Completed/Message"), rl.GetString("LoadingFolder/Title"));
                await dialog.ShowAsync();
            }
            await BookShelfStorage.SaveAsync();
        }