<Window x:Class="WpfApplication28.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation"
    xmlns:data="clr-namespace:Telerik.Windows.Data;assembly=Telerik.Windows.Data"
    Title="Window1" Height="300" Width="300">
    <Grid>
        <telerik:RadGridView Name="radGridView1" AutoGenerateColumns="False" ColumnsWidthMode="Auto" CanUserFreezeColumns="False" >
            <telerik:RadGridView.Columns>
                <telerik:GridViewDataColumn UniqueName="Number" />
                <telerik:GridViewDataColumn UniqueName="Name"   />
                <telerik:GridViewDataColumn UniqueName="Email"  />
                <telerik:GridViewDataColumn UniqueName="Orders" />
            </telerik:RadGridView.Columns>
            <telerik:RadGridView.HierarchyChildTemplate>
                 <DataTemplate>
                    <telerik:GridViewDataControl                                                     CanUserFreezeColumns="False">
                        <telerik:GridViewDataControl.GroupDescriptions>
                            <data:RadGroupDescription PropertyName="Number">
                                <data:RadGroupDescription.AggregateFunctions>
                                <data:CountFunction FunctionName="TotalNumbers" SourceField="Number"
                                Caption="Total numbers:" />
                                <data:FirstFunction FunctionName="FirsNumber" SourceField="Number"
                                Caption="First number:" />
                                </data:RadGroupDescription.AggregateFunctions>
                            </data:RadGroupDescription>
                        </telerik:GridViewDataControl.GroupDescriptions>
                    </telerik:GridViewDataControl>
                </DataTemplate>
         </telerik:RadGridView.HierarchyChildTemplate>
        </telerik:RadGridView>
    </Grid>
</Window>
