NotificationFlyout/samples/NotificationFlyoutSample.Host/App.xaml

<Application
    x:Class="NotificationFlyoutSample.Host.App"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <Application.Resources />
</Application>