如何调用ITopologicalOperator.Union方法进行地merge polygon

<DIV class=postText>ITopologicalOperator的方法是bug非常多的，在90%的情况下能够按照你预想的工作，但是在10%的情况下，既不报错也不工作。</DIV>
<DIV class=postText>      ICursor pCursor;<BR>      featureSelect.SelectionSet.Search(null, false, out pCursor);</DIV>
<DIV class=postText>      IFeatureCursor pFeatureCursor = pCursor as IFeatureCursor;<BR>      IFeature pFeatureFirst = pFeatureCursor.NextFeature();</DIV>
<DIV class=postText>      // 开始一个编辑操作，以能够撤销<BR>      m_EditWorkspace.StartEditOperation();</DIV>
<DIV class=postText>      IGeometry pGeometryFirst = pFeatureFirst.Shape;<BR>      ITopologicalOperator2 topo_oper = (ITopologicalOperator2)pGeometryFirst;</DIV>
<DIV class=postText>      //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<BR>      //成功的可能性大一些<BR>      topo_oper.IsKnownSimple_2 = false;<BR>      topo_oper.Simplify();<BR>      pGeometryFirst.SnapToSpatialReference();</DIV>
<DIV class=postText>      //这是准备合并的图斑使用的<BR>      ITopologicalOperator2 topo_oper2;<BR>      IGeometry pGeometryNext;<BR>      IFeature pFeatureNext = pFeatureCursor.NextFeature();</DIV>
<DIV class=postText>      while (pFeatureNext != null)<BR>      {<BR>        pGeometryNext = pFeatureNext.ShapeCopy;</DIV>
<DIV class=postText>        //与上面的同理<BR>        topo_oper2 = pGeometryNext as ITopologicalOperator2;<BR>        topo_oper2.IsKnownSimple_2 = false;<BR>        topo_oper2.Simplify();<BR>        pGeometryNext.SnapToSpatialReference();</DIV>
<DIV class=postText>        //这才是合并图斑的关键<BR>        pGeometryFirst = topo_oper.Union(pGeometryNext);<BR>        pFeatureNext.Delete();</DIV>
<DIV class=postText>        pFeatureNext = pFeatureCursor.NextFeature();<BR>      }<BR>      topo_oper.IsKnownSimple_2 = false;<BR>      topo_oper.Simplify();<BR>      pFeatureFirst.Shape = pGeometryFirst;<BR>      pFeatureFirst.Store();<BR>      m_EditWorkspace.StopEditOperation();<BR></DIV>