gistfile1.cs

private void fetchFileButton_Click(object sender, RoutedEventArgs e)
        {
            //// (1) 檢查transfer request是否超過數量
            if (BackgroundTransferService.Requests.Count() >= 5)
            {
                MessageBox.Show("此應用程序的背景文件傳輸請求的最大數量已超過。");
                return;
            }


            //// (2) 創建新的transfer request
            string transferFileName = filenameTextBlock.Text;
            //將 URI 字串轉換成它的逸出表示。
            Uri transferUri = new Uri(Uri.EscapeUriString(transferFileName), UriKind.RelativeOrAbsolute);

            //創建新的transfer request
            transferRequest = new BackgroundTransferRequest(transferUri);

            // GET and POST 皆有，但是不支援FTP協定
            transferRequest.Method = "GET";

            //// (3) 設定request 1.下載目標位置 2.標籤 3.何種條件transfer可被使用
            //從URI拿取檔案的名字，並且創建一個transfers目錄下的local URI。(放在隔離存取區內)
            string downloadFile = transferFileName.Substring(transferFileName.LastIndexOf("/") + 1);

            //因為下載的檔案必須指定儲存的實體位置，上傳也需要指定實體位置
            //統一所有background tansfers使用的檔案路徑，必須存在於isolated storage的固定路徑：「/shared/transfers」之中
            //建立URI
            downloadUri = new Uri("shared/transfers/" + downloadFile, UriKind.RelativeOrAbsolute);
            transferRequest.DownloadLocation = downloadUri;//設定下載目標儲存位置

            //把抓取到的名字"picture.jpg"放入tag
            transferRequest.Tag = downloadFile;

            //設定允許傳遞的狀態
            transferRequest.TransferPreferences = TransferPreferences.AllowCellularAndBattery;


            //// (4) 啟動request
            // 加入transfer request至BackgroundTransferService 
            try
            {
                BackgroundTransferService.Add(transferRequest);
            }
            catch (InvalidOperationException ex)
            {
                MessageBox.Show("Unable to add background transfer request. " + ex.Message);
            }
            catch (Exception)
            {
                MessageBox.Show("Unable to add background transfer request.");
            }


            // Navigate back
            NavigationService.GoBack();
        }