MainPage.xaml

<Page
    x:Class="MobileSample_WinRT.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:MobileSample_WinRT"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:routing="using:ReactiveUI.Xaml"
    mc:Ignorable="d">

    <Grid Background="{StaticResource ApplicationPageBackgroundThemeBrush}">
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition Height="*" />
        </Grid.RowDefinitions>

        <StackPanel Orientation="Horizontal" Margin="0,8,0,0">
            <Button x:Name="BackButton" Style="{StaticResource BackButtonStyle}" />
            <TextBlock Style="{StaticResource HeaderTextStyle}" Text="My Cool App" />
        </StackPanel>

        <routing:RoutedViewHost Grid.Row="1" x:Name="Router" />
    </Grid>
</Page>