ITopologicalOperator接口使用方法

在空间分析中通常用到ITopologicalOperator接口，有众多的空间拓扑方法，在GIS系统中的缓冲区分析、裁剪分析、几何图形差分操作、几何图形合并操作等等。下面介绍ITopologicalOperator接口的主要方法：

http://www.cnblogs.com/alex-bn-lee/archive/2012/06/17/2552557.html#ITopologicalOperator5

但是这个接口出现问题的几率是非常大的，有时候既没有报错，但是有没有运行出结果，比如Union、merge方法，其实是在我们做拓扑之前的检查不够。导致出现这个问题。下面给出示例代码：

    ICursor pCursor;            featureSelect.SelectionSet.Search(null, false, out pCursor);                        IFeatureCursor pFeatureCursor = pCursor as IFeatureCursor;            IFeature pFeatureFirst = pFeatureCursor.NextFeature();                        // 开始一个编辑操作，以能够撤销            m_EditWorkspace.StartEditOperation();                        IGeometry pGeometryFirst = pFeatureFirst.Shape;            ITopologicalOperator2 topo_oper = (ITopologicalOperator2)pGeometryFirst;                        //ITopologicalOperator的操作是bug很多的，先强制的检查下面三个步骤，再进行操作  否则会出现标题所说的问题          topo_oper.IsKnownSimple_2 = false;        //处理之前不知道是否是简单多边形，不管是不是，第一步强制转换为非简单多边形          topo_oper.Simplify();                     //对多边形强制简单化          pGeometryFirst.SnapToSpatialReference();  //图形与坐标参考对应                       //这是准备合并的图斑使用的            ITopologicalOperator2 topo_oper2;            IGeometry pGeometryNext;            IFeature pFeatureNext = pFeatureCursor.NextFeature();                        while (pFeatureNext != null)            {              pGeometryNext = pFeatureNext.ShapeCopy;                          //与上面的同理              topo_oper2 = pGeometryNext as ITopologicalOperator2;              topo_oper2.IsKnownSimple_2 = false;              topo_oper2.Simplify();              pGeometryNext.SnapToSpatialReference();                          //这才是合并图斑的关键              pGeometryFirst = topo_oper.Union(pGeometryNext);              topo_oper = pGeometryFirst  as ITopologicalOperator2;              pFeatureNext.Delete();                          pFeatureNext = pFeatureCursor.NextFeature();            }            topo_oper.IsKnownSimple_2 = false;            topo_oper.Simplify();            pFeatureFirst.Shape = pGeometryFirst;            pFeatureFirst.Store();            m_EditWorkspace.StopEditOperation();