ArcEngine 将圆形、矩形转换为多边形 ；ICircularArc、IEnvelope转化为IPolygon

1、将ICircularArc转化为IPolygon

   1: ICircularArc pCircularArc = null;   2: IRubberBand pRubberBand = new RubberCircleClass();   3: pCircularArc = pRubberBand.TrackNew(axMapControl_Main.ActiveView.ScreenDisplay, null) as ICircularArc;   4: if (pCircularArc == null)   5:     return;   6: object missing = Type.Missing;   7: ISegmentCollection pSegmentColl = new RingClass();   8: pSegmentColl.AddSegment((ISegment)pCircularArc, ref missing, ref missing);   9: IRing pRing = (IRing)pSegmentColl;  10: pRing.Close(); //得到闭合的环  11: IGeometryCollection pGeometryCollection = new PolygonClass();  12: pGeometryCollection.AddGeometry(pRing, ref missing, ref missing); //环转面  13: IPolygon pPolygon = (IPolygon)pGeometryCollection;

2、将IEnvelope转化为IPolygon

   1: IEnvelope pEnvelope = null;   2: IRubberBand pRubberBand = new RubberEnvelopeClass();   3: pEnvelope = pRubberBand.TrackNew(axMapControl_Main.ActiveView.ScreenDisplay, null) as IEnvelope;   4: if (pEnvelope == null)   5:     return;              6: IPoint p1 = new PointClass();   7: IPoint p2 = new PointClass();   8: IPoint p3 = new PointClass();   9: IPoint p4 = new PointClass();  10: p1 = pEnvelope.UpperLeft;  11: p2 = pEnvelope.LowerLeft;  12: p3 = pEnvelope.LowerRight;  13: p4 = pEnvelope.UpperRight;  14: IPointCollection pPointCollection = new PolygonClass();  15: object missing = Type.Missing;  16: pPointCollection.AddPoint(p1, ref missing, ref missing);  17: pPointCollection.AddPoint(p2, ref missing, ref missing);  18: pPointCollection.AddPoint(p3, ref missing, ref missing);  19: pPointCollection.AddPoint(p4, ref missing, ref missing);  20: IPolygon pPolygon = (IPolygon)pPointCollection;

完成以后记得使用ITopologicalOperator.Simplify()进行处理，可以处理面自动闭合等问题

注意：在给IPointCollection添加点的时候要按照一定的顺序添加（按照顺时针或者逆时针的顺序选取起点进行添加，否则会使得图形发生变化）