Avalonia/src/Avalonia.Themes.Default/ItemsControl.xaml

<Style xmlns="https://github.com/avaloniaui" Selector="ItemsControl">
  <Setter Property="Template">
    <ControlTemplate>
      <ItemsPresenter Name="PART_ItemsPresenter"
                      Items="{TemplateBinding Items}"
                      ItemsPanel="{TemplateBinding ItemsPanel}"
                      ItemTemplate="{TemplateBinding ItemTemplate}"
                      MemberSelector="{TemplateBinding MemberSelector}"/>
    </ControlTemplate>
  </Setter>
</Style>