private async void FileTransferPage_BackRequested(object sender, BackRequestedEventArgs e) { IFileTransferService service = AppObjects.Instance.Device.GetService(InkDeviceService.FileTransfer) as IFileTransferService; if ((service != null) && service.IsStarted) { await service.StopAsync(m_cts.Token); } if (Frame.CanGoBack) { Frame.GoBack(); } }