Fires when the editor's pop-up is about to be displayed.
[DXCategory("Events")] public virtual event EventHandler BeforePopup
<DXCategory("Events")> Public Overridable Event BeforePopup As EventHandler
The BeforePopup event's data class is EventArgs.
See the RepositoryItemPopupBase.BeforePopup event, which is equivalent to the current BeforePopup event, for details and an example.