Occurs before a group of items is expanded.
public event ItemAllowEventHandler GroupExpanding
The GroupExpanding event's data class is ItemAllowEventArgs. The following properties provide information specific to this event:
The GroupExpanding event is raised before a group of data items is expanded from UI or code (ExpandGroup). You can handle this event and set its parameter's Allow property to false to prevent a group from being expanded.
When you call the ExpandAllGroups method, the GroupExpanding event is raised for each group.
After the group has been expanded, the GroupExpanded event is raised.