private async Task DownloadFiles(FileDownloadManagerContext context, IEnumerable <FileDownloadManagerItem> items) { var client = new HttpClient(); client.DefaultRequestHeaders.CacheControl = new CacheControlHeaderValue(); client.DefaultRequestHeaders.CacheControl.NoCache = true; client.DefaultRequestHeaders.Add("Connection", "Keep-alive"); if (context.Timeout != null) { client.Timeout = context.Timeout; } IEnumerable <Task> downloadTasksQuery = from item in items select ProcessUrl(context, client, item); // now execute the bunch List <Task> downloadTasks = downloadTasksQuery.ToList(); while (downloadTasks.Count > 0) { // identify the first task that completes Task firstFinishedTask = await Task.WhenAny(downloadTasks); // process only once downloadTasks.Remove(firstFinishedTask); await firstFinishedTask; } }
private async Task ProcessUrl(FileDownloadManagerContext context, HttpClient client, FileDownloadManagerItem item) { try { Task <Stream> task = client.GetStreamAsync(item.Url); await task; int count; bool canceled = false; byte[] bytes = new byte[_bufferSize]; using (var srcStream = task.Result) using (var dstStream = File.OpenWrite(item.Path)) { while ((count = srcStream.Read(bytes, 0, bytes.Length)) != 0 && !canceled) { dstStream.Write(bytes, 0, count); if (context.CancellationToken != null && context.CancellationToken.IsCancellationRequested) { canceled = true; } } } item.Success = (!task.IsFaulted && !canceled); } catch (SmartException exc) { item.Success = false; item.ErrorMessage = exc.ToAllMessages(); var webExc = exc.InnerException as WebException; if (webExc != null) { item.ExceptionStatus = webExc.Status; } } }
/// <summary> /// Start asynchronous download of files /// </summary> /// <param name="context">Download context</param> /// <param name="items">Items to be downloaded</param> public async Task DownloadAsync(FileDownloadManagerContext context, IEnumerable <FileDownloadManagerItem> items) { await DownloadFiles(context, items); }