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;

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）