public async Task StarDownload(string fileName, Uri uri) { fileName = _utilityHelper.ReplaceInvalidCharactorsInFileName(fileName); //创建文件 //td:此处添加文件存在检测逻辑 var file = await _storageService.CreaterFile(defaultFolder, fileName); var downloadinfo = await _downloadService.CreateDownload(uri, file, DownloadProgress); DownloadingVM.DownloadOperations.Add(downloadinfo); try { await downloadinfo.Start(); //下载完成动作 DownloadingVM.DownloadOperations.Remove(downloadinfo); FinishedDownload(downloadinfo); } catch (TaskCanceledException) { } }