问房间体积计算-奇怪的行为&获得房间实体最准确的方法是什么？

EN

private static Solid _FirstSolid (Element elem)
{
    Options op = new Options();
    Solid roomSolid = (elem.get_Geometry(op) as GeometryElement).FirstOrDefault() as Solid;
    return roomSolid;   
}

using (Transaction t = new Transaction(doc,"bake Room Geometry"))
{
    t.Start();
    DirectShape ds = DirectShape.CreateElement(doc,new ElementId(BuiltInCategory.OST_GenericModel));
    ds.SetShape((new List<GeometryObject> {transSolid as GeometryObject}));
    t.Commit();
    t.Dispose();
}