¿Cómo muestro unObservableCollection<> de objetos personalizados en el Xceed WPF PropertyGrid en el que cada elemento de la lista se puede expandir para mostrar las propiedades de los objetos personalizados. (es decir:

---- PropertyGrid -----

CoreClass

(+/-) ObservableCollection <CustomClass>

(+/-) CustomClass.Object1

Propiedad1: Valor

Propiedad2: Valor

…

PropertyN: Value

(+/-) CustomClass.Object2

Propiedad1: Valor

Propiedad2: Valor

…

PropertyN: Value

Si yo uso[ExpandableObject] sobre elObservableCollection<> solo muestra la propiedad Counts.

Editar:(Código agregado)

MainWindow.xaml:

<Window x:Class="PropGridExample.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:xctk="http://schemas.xceed.com/wpf/xaml/toolkit"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:PropGridExample"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <xctk:PropertyGrid x:Name="PropertyGrid" SelectedObject="{Binding BindingItem}"></xctk:PropertyGrid>
    </Grid>
</Window>

MainWindow.xaml.cs

public partial class MainWindow : Window
{
    public MainWindow()
    {
        MainWindowViewModel mwvm = new MainWindowViewModel();
        this.DataContext = mwvm;
        InitializeComponent();
    }
}

MainWindowViewModel.cs

public class MainWindowViewModel
{
    public Item BindingItem { get; set; }

    public MainWindowViewModel()
    {
        BindingItem = new Item();
    }

    public class Item
    {
        public int ID { get; set; }
        [ExpandableObject()]
        public ObservableCollection<CustomClass> Classes { get; set; }

        public Item()
        {
            ID = 1;
  ,          Classes = new ObservableCollection<CustomClass>();
            Classes.Add(new CustomClass() { Name = "CustomFoo" });
        }
    }

    public class CustomClass
    {
        public string Name { get; set; }
        [ExpandableObject()]
        public ObservableCollection<type> Types { get; set; }

        public CustomClass()
        {
            Types = new ObservableCollection<type>();
            Types.Add(new type() { name = "foo", value = "bar" });
            Types.Add(new type() { name = "bar", value = "foo" });
        }
    }

    public class type
    {
        public string name { get; set; }
        public string value { get; set; }
    }
}