<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}">

         <xcdg:DataGridCollectionViewSource.ItemProperties>

            <xcdg:DataGridItemProperty Name="Freight"

                                       GroupSortStatResultPropertyName="AVERAGE_FREIGHT"/>                                        

         </xcdg:DataGridCollectionViewSource.ItemProperties>

         <xcdg:DataGridCollectionViewSource.StatFunctions>

            <xcdg:AverageFunction SourcePropertyName="Freight"

                                  ResultPropertyName="AVERAGE_FREIGHT"/>

         </xcdg:DataGridCollectionViewSource.StatFunctions>

         <xcdg:DataGridCollectionViewSource.GroupDescriptions>

            <xcdg:DataGridGroupDescription PropertyName="EmployeeID"/>

         </xcdg:DataGridCollectionViewSource.GroupDescriptions>

      </xcdg:DataGridCollectionViewSource>

   </Grid.Resources>

   <xcdg:DataGridControl x:Name="OrdersGrid"

                         ItemsSource="{Binding Source={StaticResource cvs_orders}}">

      <xcdg:DataGridControl.Columns>

         <xcdg:Column FieldName="Freight"/>

      </xcdg:DataGridControl.Columns>

      <xcdg:DataGridControl.DefaultGroupConfiguration>

         <xcdg:GroupConfiguration InitiallyExpanded="False">

            <xcdg:GroupConfiguration.Footers>

               <xcdg:GroupHeaderFooterItemTemplate VisibleWhenCollapsed="True">

                  <DataTemplate>

                     <xcdg:StatRow>

                        <xcdg:StatCell FieldName="Freight"

                                       ResultPropertyName="AVERAGE_FREIGHT"

                                       ResultConverterParameter="F2"/>

                     </xcdg:StatRow>

                  </DataTemplate>

               </xcdg:GroupHeaderFooterItemTemplate>

            </xcdg:GroupConfiguration.Footers>

         </xcdg:GroupConfiguration>

      </xcdg:DataGridControl.DefaultGroupConfiguration>

   </xcdg:DataGridControl>

</Grid>