Hi How could I loop through the container to get all the keys. Eg: For(int i=0;i< beambook.count();++i) Or Beambook:: iter1 = beambook.begin(), iter2 = beambook.end(); My requirement is to loop through the size and list compositeKey vs list of element Ids Thanks, UJ // define a multi_index_container with a composite key on typedef multi_index_container< Beam_entry, indexed_by< //non-unique as some might have more than ids ordered_non_unique< composite_key< Beam_entry, member<Beam_entry,unsigned int,&Beam_entry::pid>, member<Beam_entry,double,&Beam_entry::orientX>, member<Beam_entry,double,&Beam_entry::orientY>, member<Beam_entry,double,&Beam_entry::orientZ>, member<Beam_entry,double,&Beam_entry::OffsetA>, member<Beam_entry,double,&Beam_entry::OffsetB> > >, ordered_unique< member<Beam_entry,unsigned int,&Beam_entry::eid> > >
beambook;