关于融合同层中两条polyline要素的问题，请大侠们为小弟指点！

<P>各位大虾，我是信任。我想在同层中，融合两条polyline要素，参考了帮助文档中的一些代码，写了如下代码。但一点效果都没有，请大虾们</P>

<P>请大虾们帮小弟看看！多谢了！</P>
<P>代码：</P>
<P>Private Sub Command2_Click()<BR>    <BR>    Dim pGeoBag As IGeometryBag<BR>    Dim pEnumGeometry As IEnumGeometry<BR>    Dim pGeo As IGeometry, i As Long<BR>    Dim pPolyLineU As IPolyline<BR>    Dim pTopoOp As ITopologicalOperator2<BR>    Set pGeoBag = CreateGeometryBag<BR>    Set pEnumGeometry = pGeoBag<BR>    'Reset the enumratorpEnumGeometry.Reset<BR>    'Print the number of geometries<BR>    Debug.Print "Number of geometries : " ; pEnumGeometry.Count<BR>    'Loop over the enumerator and print the geometrytype of each geometry<BR>    Set pGeo = pEnumGeometry.Next<BR>    While Not pGeo Is Nothing<BR>        Debug.Print "Geometry: " ; i ; " Geometry type: " ; pGeo.GeometryType<BR>        i = i + 1<BR>        Set pGeo = pEnumGeometry.Next<BR>    Wend<BR>    <BR>    Set pPolyLineU = New Polyline<BR>    Set pTopoOp = pPolyLineU<BR>    pTopoOp.ConstructUnion pEnumGeometry</P>
<P>End Sub</P>

<P>Private Function CreateGeometryBag() As IGeometryBag</P>
<P>    Dim pGeoColl As IGeometryCollection, pPointColl0 As IPointCollection</P>
<P>    Dim pPointColl1 As IPointCollection<BR>    <BR>    Dim pMap As IMap<BR>    Dim pEnumFeature As IEnumFeature<BR>    Dim pEnumFeatureSetup As IEnumFeatureSetup<BR>    Dim pFeature As IFeature<BR>    Dim pRowSubtypes As IRowSubtypes<BR>    Dim pFC As IFeatureClass</P>
<P>    <BR>    Set pGeoColl = New GeometryBag<BR>    <BR>    Set pMap = MapControl1.Map<BR>    Set pEnumFeature = pMap.FeatureSelection<BR>    Set pEnumFeatureSetup = pEnumFeature 'QI<BR>        pEnumFeatureSetup.AllFields = True<BR>'    pEnumFeature.Reset<BR>    Set pFeature = pEnumFeature.Next<BR>    'Get the ObjectClassID and Subtype of the first feature in the Enum. Check all of there features against<BR>    'this one in the Do..Loop that follows.<BR>    Set pFC = pFeature.Class</P>
<P>    <BR>    Do While (Not pFeature Is Nothing)<BR>      Set pPointColl0 = pFeature.ShapeCopy<BR>      pGeoColl.AddGeometry pPointColl0<BR>      Set pFeature = pEnumFeature.Next<BR>    Loop<BR>    Set CreateGeometryBag = pGeoColl<BR>    <BR>End Function</P>