关于获取线型ID的问题

panpancat

AcDbLinetypeTable *pLinetypeTable;

AcDbObjectId CenterLId;

acdbHostApplicationServices()->workingDatabase()->getLinetypeTable(pLinetypeTable, AcDb::kForRead);

pLayerTableRecord->setLinetypeObjectId(CenterLId);

pLinetypeTable->close();

刚刚开始学习ARX，程序没办法获得中心线的ID啊，线宽设的是1mm，画出来是实线……请教各位高手，是怎么回事啊？