The BeginUpdate and EndUpdate methods call SetUpdate state when an update operation first starts or finally stops. If the calls to BeginUpdate and EndUpdate are nested, SetUpdate is only called by the first BeginUpdate call and the last EndUpdate call. 

In TAbstractNamedVariants, SetUpdateState does nothing. Descendant classes can override this method to respond in some way (such as enabling or suppressing repaints of a control that displays the values in the list) when an update operation begins or ends. 

BeginUpdate 

EndUpdate