ArcEngine组合选中相邻图形

1、获取选中图形：ISelectionSet pSelSet = (pFeaLyr as IFeatureSelection).SelectionSet;

        pSelSet.Search(null, false, out pCursor);
                              IFeatureCursor pFeaCursor = pCursor as IFeatureCursor;

2、利用Union工具组合所有图形

            IGeometryBag pGeoBag = new GeometryBagClass();
            IGeometryCollection pGeoCol = pGeoBag as IGeometryCollection;

3、判断是否为外环图形：

                    IPolygon pGeoPolygon = pGeometry as IPolygon;
          &