public sealed partial class MainPage : Page
    {
        static StorageFolder currentFolder = KnownFolders.PicturesLibrary;

        public MainPage()
        {
            this.InitializeComponent();
        }

        private async void ButtonBase_OnClick(object sender, RoutedEventArgs e)
        {
            await UpdateList();
        }

        private static async Task<List<string>> GetSubFoldersNames()
        {
            if (currentFolder != null)
            {
                var folderList = await currentFolder.GetFoldersAsync();

                currentFolder = folderList.FirstOrDefault();

                return folderList.Select(x => x.DisplayName).ToList();
            }
            else
            {
                return new List<string>();
            }
        }

        private async Task UpdateList()
        {
            var list = await GetSubFoldersNames();
            FoldersListView.ItemsSource = new ObservableCollection<string>(list);

        }