Question

I run into the following issue semi-regularly: I make changes to XAML or some resources used by it and when I go to load up the Silverlight project in debug mode it only gets as far as the spinning Silverlight-loading animation.

I’ve tried attaching the VS08 debugger to the process but it doesn’t do anything at this point (works fine once I’m in the Silverlight but not before.)

From previous experience I’ve noticed this happens when there’re problems with the XAML or the resources in it but my only solution so far has been to dissect the code line-by-line until I spot the problem.

Is there an easy way to debug/diagnose these situations?

UPDATE

I found this question with some help, but it still doesn’t provide a good way to debug these types of issues.

Answer 1

This has been a real pain to debug but I finally found the problem hidden deep in the constructor to one of our custom controls (which was looking for a resource that wasn’t there.) The real problem isn’t fixing the issue but finding it.

I found that IE responds to exceptions in passed from Silverlight to the DOM but you don’t get that same sort of feedback in the Chrome browser (which I use.) A solution that actually helps a great deal (even moreso than the IE tip) is to modify the ReportErrorToDOM() method in App.xaml.cs to the following:

private void ReportErrorToDOM(ApplicationUnhandledExceptionEventArgs e)
{
    string errorMsg = String.Empty;
    try
    {
        errorMsg = e.ExceptionObject.Message + e.ExceptionObject.StackTrace;
        errorMsg = errorMsg.Replace('"', '\'').Replace("\r\n", @"\n");

        System.Windows.Browser.HtmlPage.Window.Eval("throw new Error(\"Unhandled Error in Silverlight Application " + errorMsg + "\");");
    }
    catch (Exception)
    {
#if DEBUG
        MessageBox.Show(errorMsg);
#endif
    }
}

This gives you the position in the XAML where the issue is starting. It’s not an ideal debugger, but it does help.