<Grid xmlns:xcdg="http://schemas.xceed.com/wpf/xaml/datagrid">
  <Grid.Resources>
    <xcdg:DataGridCollectionViewSource x:Key="cvs_orders"
                                       Source="{Binding Source={x:Static Application.Current},
                                                        Path=Orders}" />

    <Style x:Key="itemIndexSelectorStyle"
           TargetType="{x:Type xcdg:RowSelector}">
      <Setter Property="Content"
              Value="{Binding RelativeSource={RelativeSource Self}, Path=ItemIndex}"/>
    </Style>
    <Style TargetType="{x:Type xcdg:DataRow}">
      <Setter Property="xcdg:RowSelector.RowSelectorStyle"
              Value="{StaticResource itemIndexSelectorStyle}" />
    </Style>
  </Grid.Resources>

  <xcdg:DataGridControl x:Name="OrdersGrid"
                            ItemsSource="{Binding Source={StaticResource cvs_orders}}" />
</Grid>