SecondaryWindowTemplate.xaml

<UserControl
    x:Class="DevHome.Common.Windows.SecondaryWindowTemplate"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    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">
    <Grid
        Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
        <Grid.RowDefinitions>
            <RowDefinition Height="auto"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>
        
        <!-- Title bar -->
        <ContentControl
            x:Name="WindowTitleBar"
            IsTabStop="False"
            HorizontalContentAlignment="Stretch"
            VerticalContentAlignment="Stretch"
            Content="{x:Bind TitleBar, Mode=OneWay}"/>

        <!-- Main content -->
        <ContentControl
            Grid.Row="1"
            IsTabStop="False"
            HorizontalContentAlignment="Stretch"
            VerticalContentAlignment="Stretch"
            Content="{x:Bind MainContent, Mode=OneWay}"/>
    </Grid>
</UserControl>