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);
}