Engine中如何根据道路中心线获取其两侧道路？

IConstructCurve pCurve1 = new PolylineClass(); 

pCurve1.ConstructOffset(pLline1， pBufferDis， ref o， ref o); 

IPolyline pline1 = pCurve1 as IPolyline; 

IConstructCurve pCurve2 = new PolylineClass(); 

pCurve2.ConstructOffset(pLline1， -1 * pBufferDis， ref o， ref o); 

IPolyline pline2 = pCurve2 as IPolyline;