AO中如何判斷polyline的類型

遇到這樣一個問題，如何判斷得到的polyline對象是否為圓弧，簡單思考後直接判斷polyline的gemetryType，但是這是錯誤的。
正確的方法是qi得到對應的ISegmentCollection介面，查詢segmentCollection中每個segment的gemetryType，可以判斷polyline的構造線型.
原因倒是很簡單，複雜的polyline可以看成是多個segment的集合，但是當前我的每個polyline對象都是由一個segment構成，所以可以按如下方式寫代碼:
  ipPolylineFeatureClass->Search(NULL,VARIANT_FALSE,&ipFeatureCursor);

                ipFeatureCursor->NextFeature(&ipFeature);
              
    IGeometryPtr ipGeometry;
                IPolylinePtr ipPolyline;
    long  lOID;
    esriGeometryType   enuGeomType;
       ipFeature->get_Shape(&ipGeometry);
                ipFeature->get_OID(&lOID);
              
   // ipGeometry->get_GeometryType(&enuGeomType);
                IGeometryCollectionPtr ipGeometryCollection;
                hr=ipGeometry->QueryInterface(IID_IPolyline,(void**)&ipPolyline);
                if(FAILED(hr))
       return ;
              
    hr=ipPolyline->QueryInterface(IID_IGeometryCollection,(void**)&ipGeometryCollection);
                if(FAILED(hr))
       return ;
    long lGeometryCount;
       hr= ipGeometryCollection->get_GeometryCount(&lGeometryCount);
                if(FAILED(hr))
       return ;
               
                ISegmentCollectionPtr ipSegmentCollection;
                ipSegmentCollection=ipGeometry;
                long lSegmentCount;
                ipSegmentCollection->get_SegmentCount(&lSegmentCount);
                if(FAILED(hr))
       return ;
    ISegmentPtr ipSegment;
                ipSegmentCollection->get_Segment(0,&ipSegment);
                if(FAILED(hr))
       return ;
    esriGeometryType   enuSegmentGeomType;
               hr= ipSegment->get_GeometryType(&enuSegmentGeomType);
                if(FAILED(hr))
       return ;