delphi 怎么能以逗号为准把字符串拆分？

var
List: TStringList;
begin
List := TStringList.Create;
List.Delimiter := ',';
List.DelimitedText := 'aaa,bbb,ccc,ddd';

ShowMessage(IntToStr(List.Count)); //4
ShowMessage(List[0]); //aaa
List.Free;
end;