MainWindow.xaml

<Window xmlns:dxg="http://schemas.devexpress.com/winfx/2008/xaml/grid"  
        x:Class="WpfApplication18.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="450" Width="800">
    <Window.Resources>
        <DataTemplate x:Key="EmployeeNotes">
            <TextBlock Text="{Binding Path=Notes}" TextWrapping="Wrap" Padding="4"/>
        </DataTemplate>
    </Window.Resources>
    <Grid>
        <dxg:GridControl x:Name="grid" AutoGenerateColumns="AddNew">
            <dxg:GridControl.View>
                <dxg:TableView DetailHeaderContent="Employees" AutoWidth="True" ShowGroupPanel="False"/>
            </dxg:GridControl.View>
            <dxg:GridControl.DetailDescriptor>
                <dxg:TabViewDetailDescriptor>
                    <dxg:DataControlDetailDescriptor ItemsSourcePath="Orders">
                        <dxg:DataControlDetailDescriptor.DataControl>
                            <dxg:GridControl AutoGenerateColumns="AddNew">
                                <dxg:GridControl.View>
                                    <dxg:TableView DetailHeaderContent="Orders" AutoWidth="True" ShowGroupPanel="False"/>
                                </dxg:GridControl.View>
                            </dxg:GridControl>
                        </dxg:DataControlDetailDescriptor.DataControl>
                    </dxg:DataControlDetailDescriptor>
                    <dxg:ContentDetailDescriptor ContentTemplate="{StaticResource EmployeeNotes}" HeaderContent="Notes"/>
                </dxg:TabViewDetailDescriptor>
            </dxg:GridControl.DetailDescriptor>
        </dxg:GridControl>
    </Grid>
</Window>