Unhandled exception at 0x7B657FD9 (Microsoft.ui.xaml.dll)

Question

I am trying to create a login system for a uwp(winui3) app. In the login window the user enters his credentials and on clicking the login button he/she is redirected to mainwindow. But I get an Unhandled exception error.

App.xaml.cs

 protected override void OnLaunched(Microsoft.UI.Xaml.LaunchActivatedEventArgs args)
    {
        loginpage=new LoginWindow();
        loginpage.Activate();}
     

LoginWindow.xaml.cs

        private void Login_Click(object sender, RoutedEventArgs e)
    {
        string query = "select * from ***** where username='" + username.Text + "' and password='" + password.Text + "'";
        DataTable dt = new DataTable();
        dt = Tools.getdatafromDATABASE(query);
        if (dt.Rows.Count == 0)
        {
        //Display incorrect username and password message
        }
        else
        {
           //Redirect to MainWindow
           Window mainwindow = new MainWindow();
            mainwindow.Activate();
        }
    }
    }

MainWindow.cs

        public MainWindow()
    {
        this.InitializeComponent();
        MainContent.Navigate(typeof(HomePage));
    }

Exception

Answer 1

Multiple top-level windows are not supported in Win UI 3 / Windows App SDK 1.0. Maybe in 1.1, at least Microsoft promised so.

You can use a ContentDialog for your login window.