autocad2008利用objectarx二次開發，從畫出的圓中得到它的圓心坐標和半徑，怎樣編程實現

{

ads_name ent;

ads_point p1;

while(acedEntSel(_T("\n選擇圓:"),ent,p1)==RTNORM){

AcDbObjectId id;

if(Acad::eOk != acdbGetObjectId(id,ent)) continue;

AcDbEntity* pEnt;

if (Acad::eOk != acdbOpenAcDbEntity( pEnt, id, AcDb::kForRead, Adesk::kFalse )) continue;

if(pEnt->isKindOf(AcDbCircle::desc())){

AcDbCircle *pCircle = (AcDbCircle *)pEnt;

double radius = pCircle->radius();

AcGePoint3d pCen = pCircle->center();

CString msg;

msg.Format(_T("圓心：(%.f,%.f), 半徑：%.f"),pCen.x,pCen.y,radius);

AfxMessageBox(msg);

}

else

{

AfxMessageBox(_T("不是圓弧！"));

}

pEnt->close();

}

return;

}