Question

I need to download several HTML files in my ASP.NET application. The average file size is about 100 KB.

Right now I’m using the following code.

    foreach (var item in items)
    {
        string url = (string)item.Element("link");
        string title = (string)item.Element("title");
        string fileName = Server.MapPath(title + ".html");

        // Add the attachement
        WebClient client = new WebClient();
        client.Encoding = System.Text.Encoding.UTF8;
        client.DownloadFileCompleted += new AsyncCompletedEventHandler((a, b) =>
        {
            System.Threading.Thread.Sleep(2000);
            message.Attachments.Add(new Attachment(fileName));
            counter++;

            // If we've downloaded all the items, send the message with the items attached to it
            if (counter == totalItems)
            {
                SendMessage(message);
            }
        });
        client.DownloadFileAsync(new Uri(url), fileName); 
    }

As you can see I’m downloading the files asynchronously, but the foreach loop doesn’t care that the file hasn’t been downloaded yet, it goes to the next iterated item.

As a result of this, some of the files are not downloaded.

Answer 1

If you’re using .NET Framework 4 you could use Task class and WaitAll method.