wpf mvvm(prism)

mainwindow.xml.cs

 public partial class MainWindow : MetroWindow
 {
     private readonly IRegionManager regionManager;
     public MainWindow(IRegionManager regionManager)
     {
         InitializeComponent();
         this.regionManager = regionManager;
     }


     private void Button_Click(object sender, RoutedEventArgs e)
     {
         regionManager.RequestNavigate("ContentRegion", nameof(DefaultView));
     }

     private void MetroWindow_Loaded(object sender, RoutedEventArgs e)
     {
         regionManager.RequestNavigate("ContentRegion", nameof(DefaultView));
     }
 }

 app.xml.cs

public partial class App
{
    protected override Window CreateShell()
    {
        return Container.Resolve<MainWindow>();
    }

    protected override void RegisterTypes(IContainerRegistry containerRegistry)
    {
        containerRegistry.RegisterSingleton<AppDbContext>(sp =>
        {
            var options = new DbContextOptionsBuilder<AppDbContext>()
                .UseSqlServer("Server=127.0.0.1;Database=db1;User Id=sa;Password=123456;")
                .Options;
            return new AppDbContext(options);
        });
        containerRegistry.RegisterForNavigation<DefaultView>();
    }
}