livexaml-container.cs

class MyView : View, IElementController
{
    public static BindableProperty HostedPageProperty = BindableProperty.Create("HostedPage", typeof(Page), typeof(MyView), propertyChanged: OnHostedPageChanged);

    ReadOnlyCollection<Element> _logicalChildrenInner = new ReadOnlyCollection<Element>(new List<Element>());
    ReadOnlyCollection<Element> IElementController.LogicalChildren => _logicalChildrenInner;

    public void SetHostedPage(Page page)
    {
        _logicalChildrenInner = new ReadOnlyCollection<Element>(new List<Element>(new[] { page } ));
    }

    private static void OnHostedPageChanged(BindableObject bindable, object oldValue, object newValue)
    {
        var myView = (MyView)bindable;
        myView.SetHostedPage((Page)newValue);
    }
}