MainPage.xaml

<Page
    x:Class="App1.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:notv1709="http://schemas.microsoft.com/winfx/2006/xaml/presentation?IsApiContractNotPresent(Windows.Foundation.UniversalApiContract, 5)"
    xmlns:v1709="http://schemas.microsoft.com/winfx/2006/xaml/presentation?IsApiContractPresent(Windows.Foundation.UniversalApiContract, 5)"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d"
    Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">

    <Grid>
        <TextBlock notv1709:Text="Test not 1709" v1709:Text="Test 1709"/>
    </Grid>
</Page>