ITopologicalOperator接口

//拓扑接口cut方法（因为会出现两个不连接的图斑算一个要素的情况，所以复杂多边形或者多部分多边形要谨慎使用）
public List<IGeometry> Cut(List<IFeature> Polygon, List<IPolyline> pFishNetList)
        {
            List<IGeometry> NewPolygon = new List<IGeometry>();
            //每一条线依次切割所有多边形
            IGeometry leftGeom;
            IGeometry rightGeom;
            //把IFeature全部转成IGeometry
            for (int i = 0; i < Polygon.Count;i++ )
            {
                IGeometry pGeo = Polygon[i].Shape as IGeometry;
                NewPolygon.Add(pGeo);
            }
            for (int i = 0; i < pFishNetList.Count;i++ )
            {
                List<int> index = new List<int>();//存储被替换掉的原多边形
                for (int j = 0; j < NewPolygon.Count; j++)
                {
                    IGeometry pGeometry = NewPolygon[j];
                    ITopologicalOperator pTopoOpe = (ITopologicalOperator)pGeometry;
                    pTopoOpe.Simplify();
                    //pGeometry本身的SpatialReference是unknow，必须要设置成跟pFishNetList[i]一致，否则下面Crosses判断会报错
                    pGeometry.SpatialReference = pFishNetList[i].SpatialReference;
                    IRelationalOperator pRelOperator = pGeometry as IRelationalOperator;

                    IArea pArea = pGeometry as IArea;//判断面积是否是平均值的两倍
                    double area = pArea.Area;
                    if (pRelOperator.Crosses(pFishNetList[i] as IGeometry) && (area >= MeanArea))
                    {
                        pTopoOpe.Cut(pFishNetList[i], out leftGeom, out rightGeom);                       
                        index.Add(j);//记录要被替换的多边形的序号
                        NewPolygon.Add(leftGeom);
                        NewPolygon.Add(rightGeom);
                    }
                }
                for (int k = index.Count-1; k > -1; k--)
                {
                    NewPolygon.RemoveAt(index[k]);//删除掉那些多边形
                }
                index.Clear();//清空，下次再用
            }
            return NewPolygon;
        }

注：（上图中的overlap判断可能会有问题，有时候有重叠却也返回false，
所以下面Intersect方法的时候判断改成了多边形外环是否大于0，等于0即没有外环，是空的）

//为了避免Cut方法的缺陷，用ITopologicalOperator的Intersect方法（面切割面）

/////////////////////////////////////////////////////////////////////////////
public List<IGeometry> Intersect(List<IFeature> Polygon, List<IPolygon> pEnvelopeList)
        {
            List<IGeometry> pIntersectList = new List<IGeometry>();
            List<IGeometry> NewPolygonList = new List<IGeometry>();//存面积大于平均值的多边形（因为类型要转成IGeometry）
            List<IGeometry> OriPolygonList = new List<IGeometry>();//存面积xiaoyu平均值的多边形
            //把IFeature(Polygon)全部转成IGeometry
            for (int i = 0; i < Polygon.Count; i++)
            {
                IArea pArea = Polygon[i].Shape as IArea;//判断面积是否是平均值的两倍
                double area = pArea.Area;
                IGeometry pGeo = Polygon[i].Shape as IGeometry;
                if (area >= MeanArea)
                {                   
                    NewPolygonList.Add(pGeo);
                }
                else
                {
                    OriPolygonList.Add(pGeo);
                }
            }
            for (int i = 0; i < pEnvelopeList.Count; i++)
            {
                for (int j = 0; j < NewPolygonList.Count; j++)
                {
                    //拓扑切割方法intersect
                    ITopologicalOperator pTopoOpe = (ITopologicalOperator)NewPolygonList[j];
                    pTopoOpe.Simplify();
                    //pGeometry本身的SpatialReference是unknow，必须要设置成跟pFishNetList[i]一致，否则下面Crosses判断会报错
                    NewPolygonList[j].SpatialReference = pEnvelopeList[i].SpatialReference;
                    IRelationalOperator pRelOperator = NewPolygonList[j] as IRelationalOperator;

                    IPolygon resultPolygon = new PolygonClass();
                    resultPolygon = pTopoOpe.Intersect(pEnvelopeList[i].Envelope as IGeometry, esriGeometryDimension.esriGeometry2Dimension) as IPolygon;
                    
                    //判断面积是否大于平均值的一半，不到一半的不存
                    IArea pArea = resultPolygon as IArea;
                    double area = pArea.Area;
                    if (resultPolygon.ExteriorRingCount != 0 && (area>(MeanArea/2)))//这句前面一个判断是防止它把空的图形也存进来
                    {
                    pIntersectList.Add(resultPolygon as IGeometry);
                    }
                }
            }
            foreach(IGeometry geo in OriPolygonList)
            {
                pIntersectList.Add(geo);//把不用切割的小图形也存进来，不管大小，都作为一个图形存起来
            }
            return pIntersectList;
        }

//合并两个要素为一个用拓扑接口Union方法
public IGeometry Union(List<IPolyline> FishNetList)
        {
            IGeometry pUnion = null;
            IGeometry pGeometry = FishNetList[0] as IGeometry;
            for (int i = 1; i < FishNetList.Count;i++ )
            {                
                ITopologicalOperator pTopoOpe = (ITopologicalOperator)pGeometry;
                pTopoOpe.Simplify();
                (FishNetList[i] as ITopologicalOperator).Simplify();
                pUnion = pTopoOpe.Union(FishNetList[i] as IGeometry);
                pGeometry = pUnion;
            }
            return pUnion;
        }