/// <summary>
 /// Called when file has been picked successfully
 /// </summary>
 /// <param name="args">file picker event args</param>
 private void OnFilePicked(FilePickerEventArgs args)
 {
     this.Handler?.Invoke(null, args);
 }
 /// <summary>
 /// Signals event that file picking has finished
 /// </summary>
 /// <param name="args">file picker event args</param>
 private static void OnFilePicked(FilePickerEventArgs args)
 {
     FilePicked?.Invoke(null, args);
 }