WPF - DispatcherUnhandledException does not seem to work

Question

I started a new WPF project in VS2008 and then added some code to trap DispatcherUnhandledException. Then I added a throw exception to Window1 but the error is not trapped by the handler. Why?

   public App()
    {
        this.DispatcherUnhandledException += new DispatcherUnhandledExceptionEventHandler(App_DispatcherUnhandledException);

    }

    void App_DispatcherUnhandledException(object sender, DispatcherUnhandledExceptionEventArgs e)
    {
        System.Windows.MessageBox.Show(string.Format("An error occured: {0}", e.Exception.Message), "Error");
        e.Handled = true;
    }

 void Window1_MouseDown(object sender, MouseButtonEventArgs e)
    {
        throw new NotImplementedException();
    }

Answer 1

This can happen because of the way you have the debugger handling exceptions -- Debug/Exceptions... should allow you to configure exactly how you want it handled.