Occurs after a group of items has been collapsed.
public event ItemEventHandler GroupCollapsed
The GroupCollapsed event's data class is ItemEventArgs. The following properties provide information specific to this event:
The GroupCollapsed event is raised after a group of data items is collapsed from the UI or code (CollapseGroup). This event serves as a notification and does not allow you to cancel the action. To prevent a group from being collapsed, handle the GroupCollapsing event and set its parameter's Allow property to false.
When you call the CollapseAllGroups method, the GroupCollapsed event is raised for each group.