I\'m using the following code for to open a window in a separate thread
public partial class App : Application
{
protected override void OnStartup(Startu
why you trying to do this? there is (nearly)no reason to run a 2end UI thread inside you application ... if you want a non Modal new Window, instantiate you window and call show.
Why nearly? Because this is a very complex topic and unless you have a huge budged to develop exactly this behavior, you can live without it.