Engine中如何调整DataFrame大小使其与Page一样大？

IEnvelope envelope = _pPageLayoutControl.Page.PrintableBounds; 

IGraphicsContainer GC = _pPageLayoutControl.ActiveView as IGraphicsContainer; 

GC.Reset(); 

IElement element = GC.Next(); 

if (element is IMapFrame) 

{ 

element.Geometry = envelope as IGeometry; 

GC.UpdateElement(element); 

}