RequiredHeaderTemplate and BoldHeaderTemplate for XAML #UWP

MainPage.xaml

<Page x:Class="App18.MainPage"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:local="using:App18"
      xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
      xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
      mc:Ignorable="d">
    <Page.Resources>

        <FontWeight x:Key="HeaderFontWeight">Medium</FontWeight>

        <DataTemplate x:Key="RequiredHeaderTemplate">
            <StackPanel Orientation="Horizontal">
                <TextBlock Text="{Binding}"
                           FontWeight="{StaticResource HeaderFontWeight}" />
                <TextBlock Text="(required)"
                           FontSize="12"
                           Margin="4,0,0,1"
                           VerticalAlignment="Bottom" />
            </StackPanel>
        </DataTemplate>
        <DataTemplate x:Key="BoldHeaderTemplate">
            <TextBlock Text="{Binding}"
                       FontWeight="{StaticResource HeaderFontWeight}" />
        </DataTemplate>

    </Page.Resources>

    <Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
        <StackPanel Orientation="Vertical"
                    HorizontalAlignment="Center"
                    VerticalAlignment="Center"
                    Width="250">
            <TextBox HeaderTemplate="{StaticResource RequiredHeaderTemplate}"
                     Header="Firstname"
                     Margin="0,0,0,8"
                     InputScope="PersonalFullName" />
            <TextBox HeaderTemplate="{StaticResource RequiredHeaderTemplate}"
                     Header="Lastname"
                     Margin="0,0,0,8"
                     InputScope="PersonalFullName" />
            <TextBox HeaderTemplate="{StaticResource BoldHeaderTemplate}"
                     Header="Email"
                     Margin="0,0,0,8"
                     InputScope="EmailNameOrAddress" />
            <ComboBox HeaderTemplate="{StaticResource RequiredHeaderTemplate}"
                      Header="Department"
                      HorizontalAlignment="Stretch">
                <ComboBoxItem Content="Sales" />
                <ComboBoxItem Content="Production" />
                <ComboBoxItem Content="Marketing" />
            </ComboBox>
        </StackPanel>
    </Grid>
</Page>