Question

After searching in the Net for about 4 hours I still don’t understand Async functions on Windows Phone 7. I tried to run that code but it looks like the event “DownloadStringCompleted” for my webClient is never raised. I tried to wait here for an answer, but it just freeze my app. Anyone could help and explain why it don’t work?

    internal string HTTPGet()
    {
        string data = null;
        bool exit = false;
        WebClient webClient = new WebClient();
        webClient.UseDefaultCredentials = true;

        webClient.DownloadStringCompleted += (sender, e) =>
        {
            if (e.Error == null)
            {
                data = e.Result;
                exit = true;
            }
        };

        webClient.DownloadStringAsync(new Uri(site, UriKind.Absolute));

        //while (!exit)
        //    Thread.Sleep(1000);

        return data;
    }

Ok. Found something!
http://blogs.msdn.com/b/kevinash/archive/2012/02/21/async-ctp-task-based-asynchronous-programming-for-windows-phone.aspx
Yay! 🙂

Answer 1

Its not a problem with emulator. you want to return the data from your HttpGet() method, but the data is already returned (as null) before the actual response from the webClient occurs. hence I suggest you to make some changes to the code and try.

WebClient client = new WebClient();
client.DownloadStringCompleted += new DownloadStringCompletedEventHandler(client_DownloadStringCompleted);
client.DownloadStringAsync(new Uri(site, UriKind.Absolute));

and then in the DownloadCompleted event handler(or callback), you manupulate the actual result

void client_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
{
    var response= e.Result; // Response obtained from the site
}