c# – Xamarin Native Structure

I want some steering with respect to Xamarin Native Venture

The Plan is:

1. UI Growth:

• Xamarin.iOS with its unbiased UI – ie: UITableView / UICollectionViews, and many others
• Xamarin.Android with its unbiased UI – ie: Listview and Adapters / RecyclerView, and many others

2. Structure:

• MvvM with none framework simply the plain MvvM patterm
• Just like Xamarin.Varieties the place we set first web page in App.xaml.cs

public partial class App : Utility
    {

        public App()
        {
            InitializeComponent();
            MainPage = new MainPage();
        }
}

Which suggests,

How do I set my first ViewModel as begin web page for each iOS and android in App.cs

For my Xamarin Native App.

With out utilizing any MvvM framework eg: MvvMCross / MvvMPrism / MvvMLite

Thanks All.