ae开发union合并异常来自 HRESULT:0x80040218

Question

                        pMap = axMapControl1.Map;
                        pActiveView = pMap as IActiveView;
                        pEnv = axMapControl1.TrackRectangle();
                        enumelement = pGraphicsContainer.LocateElementsByEnvelope(pEnv);
                        IElement ele1 = enumelement.Next();
                        IElement ele2 = enumelement.Next();
                        ITopologicalOperator topologicalOperator = (ITopologicalOperator)ele1.Geometry;
                        topologicalOperator.Simplify();
                        (ele2.Geometry as ITopologicalOperator).Simplify();
                        IGeometry unionGeometry =  topologicalOperator.Union(ele2.Geometry);
                        
                        IElement unionElement = new PolygonElementClass { Geometry = unionGeometry };
                        axMapControl1.ActiveView.GraphicsContainer.AddElement(unionElement, 0);
                        axMapControl1.ActiveView.PartialRefresh(esriViewDrawPhase.esriViewGraphics, null, null);

在地图控件中自己添加了两个多边形，在使用union方法合并时报错，在网上看到说是图形未简化处理，但在用Simplify方法简化后还是报错。