NavigationPage in Xaml

Sorry for such a simple question. What is the structure for the NavigationPage in xaml?

Among others, this is what I have tried.

<?xml version="1.0" encoding="UTF-8" ?>
<NavigationPage
    xmlns="http://xamarin.com/schemas/2014/forms"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
    x:Class="My.Shared.Page">
    <NavigationPage.Content>
            <ScrollView>
                <StackLayout x:Name="layout" Orientation="Vertical" VerticalOptions="Start" HorizontalOptions="Center">
                <ActivityIndicator x:Name="activity"></ActivityIndicator>
                </StackLayout>
            </ScrollView>
    </NavigationPage.Content>
</NavigationPage>


<?xml version="1.0" encoding="UTF-8" ?>
<NavigationPage
    xmlns="http://xamarin.com/schemas/2014/forms"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
    x:Class="My.Shared.Page">
    <NavigationPage>
        <ContentPage>
            <ScrollView>
                <StackLayout x:Name="layout" Orientation="Vertical" VerticalOptions="Start" HorizontalOptions="Center">
                <ActivityIndicator x:Name="activity"></ActivityIndicator>
                </StackLayout>
            </ScrollView>
        </ContentPage>
    </NavigationPage>
</NavigationPage>