请问ArcEngine 里如何移除整个组图层，包括这个组一起移除？

知道怎么移除了:
IGroupLayer groupLayer = mapControl.CustomProperty as IGroupLayer;
IMap map = _mapControl.Map;
IActiveView activeView = map as IActiveView;
if (map == null || groupLayer == null) return;
  map.DeleteLayer(groupLayer);
  activeView.PartialRefresh(esriViewDrawPhase.esriViewGeography, null, activeView.Extent);