c# - SqlCommand for Ior filling values to ComboBox from multiple columns -

hello friends have column cena1, cena2, cena3 , need display it's values in combobox, there way that? tried this:

 spojeni.open();  var cb4 = new sqlcommand("select cena1,cena2,cena3 zajezd akce="+zakce.text,spojeni);              sqldatareader dr4 = cb4.executereader();             while (dr4.read())             {                 combobox4.items.add(dr4["cena1,cena2,cena3"]);               }             dr4.close();             dr4.dispose(); 

but program falls. please me ?

            spojeni.close(); 

spojeni.open(); var cb4 = new sqlcommand("select cena1,cena2,cena3 zajezd akce="+zakce.text,spojeni);          sqldatareader dr4 = cb4.executereader();         while (dr4.read())         {             combobox4.items.add(dr4["cena1"].tostring() + dr4["cena2"].tostring() + dr4["cena3"].tostring());           }         dr4.close();         dr4.dispose();