<Window x:Class="WpfApplication1.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:local="clr-namespace:WpfApplication1"
    Title="Window1">
     <Grid>
         <Grid.Resources>
            <ObjectDataProvider x:Key="Customers" ObjectType="{x:Type local:DataClasses1DataContext}" MethodName="get_Customers" />
        </Grid.Resources>
        <telerik:RadGridView Name="RadGridView1" ItemsSource="{Binding Source={StaticResource Customers}}">
            <telerik:GridViewDataControl.HierarchyChildTemplate>
                <DataTemplate>
                    <StackPanel>
                        <telerik:RadGridView   
                            CanUserReorderColumns="False"  
                            CanUserFreezeColumns="False"   
                            ShowGroupPanel="False"  
                            ColumnsWidthMode="Auto"  
                            ItemsSource="{Binding Path=Orders}">
                        </telerik:RadGridView>
                    </StackPanel>
                </DataTemplate>
            </telerik:GridViewDataControl.HierarchyChildTemplate>
        </telerik:RadGridView>
    </Grid>
</Window>
