MainWindow.xaml

<Window
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:dxg="http://schemas.devexpress.com/winfx/2008/xaml/grid"
    x:Class="SaveWpfGridState.MainWindow"
    Title="MainWindow"
    Height="350" Width="525" WindowStartupLocation="CenterScreen">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition />
        </Grid.RowDefinitions>

        <StackPanel HorizontalAlignment="Left" Orientation="Horizontal">
            <Button Content="Refresh Data" Name="btnRefreshData" Click="btnRefreshData_Click"  />
        </StackPanel>

        <dxg:GridControl Grid.Row="1" Name="grdMaster" ItemsSource="{Binding Data}">

            <dxg:GridControl.DetailDescriptor>
                <dxg:DataControlDetailDescriptor ItemsSourceBinding="{Binding ChildData}">
                    <dxg:GridControl x:Name="grdDetail">
                        <dxg:GridControl.Columns>
                            <dxg:GridColumn FieldName="id" x:Name="colidChild" Visible="False" VisibleIndex="0"/>
                            <dxg:GridColumn FieldName="ChildDescription" x:Name="colChildDescription" VisibleIndex="0" />
                        </dxg:GridControl.Columns>
                        <dxg:GridControl.View>
                            <dxg:TableView x:Name="vwChild" AutoWidth="True" ShowGroupPanel="False" NavigationStyle="Row"/>
                        </dxg:GridControl.View>
                    </dxg:GridControl>
                </dxg:DataControlDetailDescriptor>
            </dxg:GridControl.DetailDescriptor>

            <dxg:GridControl.Columns>
                <dxg:GridColumn FieldName="id" x:Name="colidMaster" Visible="False"/>
                <dxg:GridColumn FieldName="MasterDescription" x:Name="colMasterDescription" VisibleIndex="0" />
                <dxg:GridColumn FieldName="GroupField" x:Name="colGroupField" VisibleIndex="1" GroupIndex="0" />
            </dxg:GridControl.Columns>

            <dxg:GridControl.View>
                <dxg:TableView x:Name="vwMaster" AutoWidth="True" NavigationStyle="Row"/>
            </dxg:GridControl.View>
        </dxg:GridControl>
    </Grid>
</Window>