private async void FileListView_OnDrop(object sender, DragEventArgs e)
        {
            if (e.DataView.Contains(StandardDataFormats.StorageItems))
            {
                var storageItems = await e.DataView.GetStorageItemsAsync();

                LocalFileCollection.AddRange(storageItems.Select(x => (StorageFile)x).ToList());
            }
        }
        private async void OnBrowseFilesButtonClicked(object sender, RoutedEventArgs e)
        {
            string[] inputFormExtensions = FormRecognizerExplorer.ImageExtensions.Concat(FormRecognizerExplorer.PdfExtensions).ToArray();
            IReadOnlyList <StorageFile> selectedFiles = await Util.PickMultipleFilesAsync(inputFormExtensions);

            if (selectedFiles != null && selectedFiles.Any())
            {
                LocalFileCollection.AddRange(selectedFiles);
            }
        }