How to expand GridItem in a PropertyGrid

See more:

C#

I write a windows application, there is a PropertyGrid on form, and I successfully implement the following line at run time to display PropertyGird on form :

PropertyGrid1.SelectedObject = ThePropertySet;

Plus, I can write a TypeConverter class to show a dropdown property, so I can select an item in the dropdown list for the property.

However, I can not write an expandable property ! I would like to have a property be expandable to include sub_properties, and I can not find a clearly and completely sample which focus on this topic, could you introduce one for my reference ? Thanks.