Why does System.Windows.MessageBox lag a WPF window?

Question

Consider the following code:

private void Window_Loaded(object sender, RoutedEventArgs e)
{
    MessageBox.Show("MyMessage");
}

If I am trying to display a message box after a WPF window has been loaded, when I run the application, the WPF window is displayed with a transparent background (only the non-client area is visible) and it takes 3-5 seconds until the message box appears. The WPF window returns to normal only after the message box has been closed.

Is this normal? Does anyone else experience this?

EDIT: I have added a screenshot of how the window looks like:

Answer 1

The MessageBox is getting shown at the Normal DispatcherPriority, which occurs before things like DataBind, Render, and Loaded, so the code that initializes your Window's objects is not getting run until after you dismiss the MessageBox

You can fix this by simply showing the MessageBox at a later DispatcherPriority, such as Background

private void Window_Loaded(object sender, RoutedEventArgs e)
{
    InitializeComponent();

    this.Dispatcher.BeginInvoke(DispatcherPriority.Background, 
        new Action(delegate() { MessageBox.Show("MyMessage"); }));
}