<ResourceDictionary
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:controls="using:Microsoft.Toolkit.Uwp.UI.Controls">
    <Style TargetType="controls:HeaderedItemsControl">
        <Setter Property="Padding" Value="2,0,0,0"/>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="controls:HeaderedItemsControl">
                    <StackPanel>
                        <ContentPresenter Content="{TemplateBinding Header}" ContentTemplate="{TemplateBinding HeaderTemplate}"/>
                        <ItemsPresenter Margin="{TemplateBinding Padding}"/>
                    </StackPanel>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</ResourceDictionary>

