如何交互生成面域对象

AcDbObjectId eId;
AcDbEntity * ent;
ads_name en;
int rc = acdbEntLast(en); //获取数据库中任意一个实体
if (rc != RTNORM)
{
acutPrintf("the database has nothing./n", rc);
}
if(!acedCommand(RTSTR,"-boundary",RTSTR,PAUSE,RTSTR,"",RTNONE))
return; //调用命令生成边界
for(;;) //边界可能是嵌套型的，也就是有孤岛，所以进行循环
{
int rc = acdbEntNext(en,en); //获取生成的边界
if (rc != RTNORM)
break; //已经没有边界实体，退出循环
acdbGetObjectId(eId, en);
acdbOpenObject(ent, eId,AcDb::kForRead);
ent->close();
if(ent->isKindOf(AcDbPolyline::desc())) //生成的应是AcDbPolyline实体
//..................
//create region object //这时就可以根据AcDbPolyline
}; //的点的信息生成面域对象