在App.xaml.cs中创建后不打开Windows

当我在app.xaml.cs中动态创建主窗口时,MainWindow.Show()函数将被忽略。每个Xaml属性(如window.height等)都设置为“NaN”。
其他窗口也一样,即使我创建了一个新窗口,其中包含一个空的xaml。

奇怪的是,如果我在while循环之前打开任何窗口,比如Window1,并显示它,while循环之后的所有窗口也将打开。

因此,我可以做一个变通方法,并初始化一个窗口,该窗口立即自动关闭。但如前所述,这只是权宜之计。

有人能回忆起这种奇怪的行为吗?

private void App_OnStartup(object sender, StartupEventArgs e)
    {
        var win = new Window1();  // if I comment out these two lines,
        win.Show();               // no Windows, except the 'Einloggen' window will be shown

        var i = 0;
        while (i < 3) // 3 mal falsch = Programm wird beendet
        {
            var login = new Einloggen();
            login.ShowDialog(); //ShowDialog is intentional, I want to wait until the user has entered his credentials, then 'login' closes automatically
            if (login.Anmeldeverusch)
            {
                if (login.TBUsername.Text != string.Empty && login.PBPasswort.Password != string.Empty)
                {
                    var log = Login(login.TBUsername.Text, login.PBPasswort.Password); //The Login(string, string) method opens a connection to the Database. If that does not throw an exception, the user is authorized to use the Program, and the method will return True
                    if (log)
                    {
                        break;
                    }
                }

                i++;
            }
            else
            {
                Environment.Exit(1);
            }
        }

        if (i > 2)
        {
            MessageBox.Show("Drei fehlgeschlagene Anmeldeversuche!");
            Environment.Exit(0);
        }

        var mainWindow = new MainWindow();
        mainWindow.Show(); // .Show and .ShowDialog() will be ignored. they dont throw an excetption. The entire program just closes after the my App_OnStartup is over
    }