<Grid xmlns:xcdg="http://schemas.xceed.com/wpf/xaml/datagrid">

  <Grid.Resources>

      <xcdg:DataGridCollectionViewSource x:Key="cvs_orderdetails"

                                         Source="{Binding Source={x:Static Application.Current}, Path=OrderDetails}">

        <xcdg:DataGridCollectionViewSource.StatFunctions>

            <xcdg:CountFunction ResultPropertyName="orderid_count"

                                SourcePropertyName="OrderID"/>

            <xcdg:SumFunction ResultPropertyName="unitprice_sum"

                              SourcePropertyName="UnitPrice"/>

            <xcdg:AverageFunction ResultPropertyName="unitprice_average"

                                  SourcePropertyName="UnitPrice"/>

            <xcdg:SumFunction ResultPropertyName="quantity_sum"

                              SourcePropertyName="Quantity"/>

        </xcdg:DataGridCollectionViewSource.StatFunctions>

        <xcdg:DataGridCollectionViewSource.GroupDescriptions>

            <xcdg:DataGridGroupDescription PropertyName="ProductID"/>

        </xcdg:DataGridCollectionViewSource.GroupDescriptions>

      </xcdg:DataGridCollectionViewSource>

      <xcdg:StatResultConverter x:Key="valueConverter"/>

      <xcdg:GroupConfiguration x:Key="quantityGroupConfiguration"

                               DefaultHeadersFootersType="None">

        <xcdg:GroupConfiguration.Headers>

            <xcdg:GroupHeaderFooterItemTemplate VisibleWhenCollapsed="True">

              <DataTemplate>

                  <xcdg:StatGroupHeaderControl ShowGroupLabel="True"

                                               AutoCreateCells="False">

                    <xcdg:StatGroupHeaderControl.Cells>

                        <xcdg:StatCell FieldName="Quantity"

                                       ResultPropertyName="quantity_sum" />

                    </xcdg:StatGroupHeaderControl.Cells>

                  </xcdg:StatGroupHeaderControl>

              </DataTemplate>

            </xcdg:GroupHeaderFooterItemTemplate>

        </xcdg:GroupConfiguration.Headers>

      </xcdg:GroupConfiguration>

  </Grid.Resources>

  <xcdg:DataGridControl x:Name="OrderDetailsGrid"

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

      <xcdg:DataGridControl.Columns>

        <xcdg:Column FieldName="Quantity"

                     Title="Quantity"

                     GroupConfiguration="{StaticResource quantityGroupConfiguration}" />

      </xcdg:DataGridControl.Columns>

  </xcdg:DataGridControl>

</Grid>