Creating a shell

The main navigation for this app will be tabs at the bottom of the screen. The app will have a fly-out menu with two options—Home and Gallery:

1. In the Views folder in the GalleryApp project, create two new ContentPage files with XAML—one named MainView and one named GalleryView.
2. At the root of the GalleryApp project, create a new ContentPage file named MainShell.
3. Change the base class of MainShell to Shell instead of ContentPage. We need to do this in both MainShell.xaml and MainShell.xaml.cs.
4. Add  MainView to the Shell object wrapped in a ShellContent object.
5. Add GalleryView to the Shell object using the ContentTemplate property of ShellContent. Use the DataTemplate mark-up extension. This will load GalleryView when the user taps the tab, instead of when Shell is loading, as is the case with MainView:

<Shell xmlns="http://xamarin.com/schemas/2014/forms"
 xmlns:x="http...