AcDbObjectId
    CTestCommands::AddToModelSpace(AcDbEntity* pEntity,AcDbDatabase* pDatabase,bool isAutoClose)
    {
        AcDbObjectId objId;  
        AcDbBlockTableRecordPointer spBlkRec(ACDB_MODEL_SPACE,pDatabase,AcDb::kForWrite);
        if(spBlkRec.openStatus() != Acad::eOk)
            return AcDbObjectId::kNull;
        spBlkRec->appendAcDbEntity(objId, pEntity);

        if(isAutoClose)
            pEntity->close();
        return objId;
    }

    // 绘制一个圆心为100,100,0.0，半径为20的半圆弧
    McGePoint3d cnePt(100,100,0.0);
    double radius   = 20.0; 
    double dSAng    = 0.0;
    double dEAng    = 3.14159265;
    McDbArc* pArc = new McDbArc(cnePt,,radius,dSAng,dEAng);
    return AddToModelSpace(pArc,pDatabase,true);