MainWindow.xaml

<Window x:Class="ChildNodesSelector.MainWindow"
        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"
        xmlns:local="clr-namespace:ChildNodesSelector"
        Title="MainWindow" Height="450" Width="700">
    <Window.DataContext>
        <local:ViewModel/>
    </Window.DataContext>
    <Window.Resources>
        <local:CustomChildrenSelector x:Key="childrenSelector"/>
    </Window.Resources>
    <Grid>
        <dxg:TreeListControl ItemsSource="{Binding DataItems}" AutoGenerateColumns="AddNew" EnableSmartColumnsGeneration="True">
            <dxg:TreeListControl.View>
                <dxg:TreeListView TreeDerivationMode="ChildNodesSelector"
                                  ChildNodesSelector="{StaticResource childrenSelector}"/>
            </dxg:TreeListControl.View>
        </dxg:TreeListControl>
    </Grid>
</Window>