ArcEngine合并线状要素的有关问题

ArcEngine合并线状要素的问题
要编码实现合并线状要素，在网上找了好多资料，大概都类似下面的代码，但是执行了之后都没什么效果，并没有合并，不知道为什么哦，请大神们给点意见吧！
//             Polyline pPolyline = null;
            ITopologicalOperator pTopologicalOperator;
            IFeature pFeatureTemp = pTypeArray[0] as IFeature;
            IGeometry pGeometry = pFeatureTemp.Shape;
            int jj = 1;
            while (jj < nFeatureCount)
            {
                pTopologicalOperator = pGeometry as ITopologicalOperator;
                pGeometry = ((IFeature)pTypeArray[jj]).Shape;
                pGeometry = pTopologicalOperator.Union(pGeometry as IGeometry);
                jj++;
            }
//             pPolyline = pGeometry as IPolyline; ArcEngine 线状要素合并 错误 Union ArcEngine编辑
[解决办法]
以前做的项目，整个合并的函数如下

     
private void MergeFeatures(List<int> OneFeatureArr
{
            IFeatureLayer tFeatureLayer = tSelectLayer as IFeatureLayer;
            IFeatureClass pFeatureClass = tFeatureLayer.FeatureClass;
            var pDataset = pFeatureClass as IDataset; 
 
            IWorkspace pWorkspace = pDataset.Workspace;       
            IFeatureWorkspace pFWs = pWorkspace as IFeatureWorkspace;
            pCommonFeaureWorkspace = pFWs;

            IWorkspaceEdit pWorkspaceEdit = (IWorkspaceEdit)pCommonFeaureWorkspace;
            pWorkspaceEdit.StartEditing(true);
            pWorkspaceEdit.StartEditOperation();

            IFeatureLayer pFeatureLayer = tSelectLayer as IFeatureLayer;
            IFeatureCursor pEF = pFeatureLayer.Search(null, false);
            IFeature pFeatureFirst = pEF.NextFeature();
            while (pFeatureFirst != null)
            {//找到在数组里的第一个要素
                if (pFeatureFirst.OID == OneFeatureArr[0])
                {
                    //OneFeatureArr.RemoveAt(0);//除掉第一个要素
                    break;
                }
                else
                    pFeatureFirst = pEF.NextFeature();
            }
            pEF = pFeatureLayer.Search(null, false);

            IGeometry pGeometryFirst = pFeatureFirst.Shape;
            ITopologicalOperator2 pTopOperatorFirst = (ITopologicalOperator2)pGeometryFirst;
            IRelationalOperator pRelOperatorFirst = (IRelationalOperator)pGeometryFirst; 
 
            pTopOperatorFirst.IsKnownSimple_2 = false;
            pTopOperatorFirst.Simplify();
            pGeometryFirst.SnapToSpatialReference();

            IGeometry pGeometrySecond=null;
            IFeature pFeatureSecond = pEF.NextFeature();

            IGeometryCollection Geometrybag = new GeometryBagClass();//装geometry的袋子
            object oMissing = Type.Missing;
            while (pFeatureSecond != null)
            {
                if (OneFeatureArr.IndexOf(pFeatureSecond.OID) == -1)
                {
                    pFeatureSecond = pEF.NextFeature();
                    continue;
                }
                pGeometrySecond = pFeatureSecond.ShapeCopy;
                Geometrybag.AddGeometry(pGeometrySecond, ref oMissing, ref oMissing);//将geometry装进袋子
                pFeatureSecond = pEF.NextFeature();
            }
            IEnumGeometry tEnumGeometry =(IEnumGeometry) Geometrybag;
            pTopOperatorFirst.ConstructUnion(tEnumGeometry);

            pTopOperatorFirst.IsKnownSimple_2 = false;
            pTopOperatorFirst.Simplify();
            pFeatureFirst.Shape = pGeometryFirst;
            pFeatureFirst.Store(); 
 

            pWorkspaceEdit.StopEditOperation();
            pWorkspaceEdit.StopEditing(true);
}