Emillio Yu-Gi-Oh! Game Deck Event crazy SQL table join blah... Version 2 optimized

var _joinedTables = from _dttFilter in _drFilter
                    join _dtDeck in _dsYgo.Tables["Deck"].AsEnumerable()
                    on int.Parse(_dttFilter["FK_Deck"].ToString())
                    equals int.Parse(_dtDeck["PK_Deck"].ToString())

                    join _dtEvent in _dtEventsTemp.AsEnumerable()
                    on (_dttFilter["FK_Event"].ToString() == "" ? -1 : int.Parse(_dttFilter["FK_Event"].ToString()))
                    equals int.Parse(_dtEvent["PK_Event"].ToString())

                    let latestDeckList = _dsYgo.Tables["DeckList"].AsEnumerable()
                        .Where(_drDeckList => _drDeckList["FK_Deck"].ToString() == _dtDeck["PK_Deck"].ToString() &&
                                              DateTime.Parse(_drDeckList["Datum"].ToString()) < DateTime.Parse(_dttFilter["Start"].ToString()))
                        .OrderByDescending(_drDeckList => DateTime.Parse(_drDeckList["Datum"].ToString()))
                        .FirstOrDefault()

                    select new
                    {
                        Start = _dttFilter["Start"],
                        End = _dttFilter["End"],
                        Deck = _dtDeck["Name"],
                        Event = _dtEvent["Name"],
                        CoinWin = _dttFilter["CoinWin"],
                        Win = _dttFilter["Win"],
                        FK_DeckList = latestDeckList != null ? latestDeckList["PK_Decklist"].ToString() : ""
                    };