主要根据IPolygon4的get_InteriorRingBag方法。
IGeometry geo = null;
IRing exring = null;
(geo as IPolygon2).QueryExteriorRings(ref exring);
IGeometryBag geobag = (geo as IPolygon4).get_InteriorRingBag(exring);
for (int i = 0; i < (geobag as IGeometryCollection).GeometryCount; i++)
{
IGeometry geotmp = (geobag as IGeometryCollection).get_Geometry(i);
geotmp.....
}