How to know value of common table field

We want to write generic class with generic table and we don't know how to do :
This is one of solution:

Public void deleteLine(Common _JournalTrans)
{
    InventDimId    InventDimId;
    ;

    InventDimId = _JournalTrans.(fieldname2id(_JournalTrans.tableId,"InventDimId"));
}