求教高手，ARCGIS一个画圆的问题

<P>public void circle2()<BR>  {esriCore.IPoint point1=new esriCore.PointClass();<BR>   point1.PutCoords(xc,yc);<BR>   esriCore.IConstructCircularArc circle1=new esriCore.CircularArcClass();<BR>   circle1.ConstructCircle(point1,5000,true);<BR>   esriCore.ISegmentCollection pPolygon=new esriCore.PolygonClass();<BR>   <FONT color=#bb44a3>pPolygon.AddSegment((esriCore.ISegment)circle1);<BR></FONT>   esriCore.ITopologicalOperator;<BR>   esriCore.ITopologicalOperator pTopoOp =(esriCore.ITopologicalOperator)pPolygon;<BR>   pTopoOp.Simplify();}<BR>在下用的是C#语言,问题出在红色部分,说那个方法需要有三个参数,方法的原形是:</P>
<P>AddSegment ( esriCore.ISegment inSegment , System.Object before , System.Object after ),但后面两个参数不知道该是什么,望高手指点.谢谢.<BR></P>