How Can i put Positions of a user into a String?

Hi everybody please answer me about putting user's positions into a string? for example a user have 2 positions :CEO and Member of board. so i need a string similar below: "CEO, Member of board" syntax of my source code is OK, but logically didn't work: thanks for(i=0; i<Me.Case.WorkingCredential.Positions.Count ;i++) { userPositions+=Me.Case.WorkingCredential.Positions+", "; }