Question

I’m writing a WP7 app which gets website information using WebClient‘s DownloadStringAsync method. The DownloadStringCompletedEventHandler parses the text before it gets displayed.

Take for example:

foo() {    
    ...
    getAllTheWebsiteInfo()
    ...
    // display the downloaded, parsed text [1]
    ...
}

getAllTheWebsiteInfo() {
    ...
    DownloadStringAsync()
    ...
}

The problem I’m running into is that at point [1] the text is empty (default value).

Is there a way for foo() to know when DownloadStringCompletedEventHandler has completed parsing the text so that at that point I can properly display the downloaded, parsed text?

Answer 1

Instead of setting the text in your foo method, you should just call the method which updates the UI at the end of your event handler, like this:

private void OnDownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
{
    DoParsingStuff(e); // do parsing stuff - may or may not be in it's own method ;)

    UpdateUI(); // this would contain your code to update the UI,
                // just as the name says
}

instead of your approach, which essentially is like this:

private void foo()
{
    // ...

    getAllTheWebsiteInfo(); // as shown above

    // ??? waiting stuff ???

    UpdateUI();
}