I have an application which uses a main window. But before showing the
Main Window (which is best done by Application.Run(new MainWindow();) I
need to show a Login Window. When the login fails, the application
should terminate but when the login is successful the loginwindow should
be destroyed and the main application window should be presented to the
user.

What is the best way to do it?
-Can I call loginwindow.Showdialog() before calling Application.Run(new
MainWindow()
-Or should I create and show the loginwindow, then call
Application.Run() without a form as parameter and within the loginwindow
either call application.exit() or instantiate the MainWindow and upon
closing the mainwindow call application.exit().
Regards
Stephan