C# Deadlock problem

static readonly object locker = new object();
 
        static List<string> EastGameList = new List<string>();
        static List<string> WestGameList = new List<string>();
        static List<string> EuropeGameList = new List<string>();
        static List<string> AsiaGameList = new List<string>();
 
        internal static string GetGameToJoin(List<SpamGame> gameList, Server realm)
        {
            //string[] GameList = gameList.ToArray();
            lock (locker)
            {
                IEnumerable<string> GameList;
                switch (realm)
                {
                    case Server.UsEast:
                        if (EastGameList.Count > 1000)
                            EastGameList.Clear();
                        GameList = from k in gameList orderby k.Players descending select k.GameName;
                        foreach (string game in GameList)
                        {
                            if (!EastGameList.Contains(game))
                            {
                                EastGameList.Add(game);
                                return game;
                            }
                        }
                        break;
                    case Server.UsWest:
                        if (WestGameList.Count > 1000)
                            WestGameList.Clear();
                        GameList = from k in gameList orderby k.Players descending select k.GameName;
                        foreach (string game in GameList)
                        {
                            if (!WestGameList.Contains(game))
                            {
                                WestGameList.Add(game);
                                return game;
                            }
                        }
                        break;
                    case Server.Europe:
                        if (EuropeGameList.Count > 1000)
                            EuropeGameList.Clear();
                        GameList = from k in gameList orderby k.Players descending select k.GameName;
                        foreach (string game in GameList)
                        {
                            if (!EuropeGameList.Contains(game))
                            {
                                EuropeGameList.Add(game);
                                return game;
                            }
                        }
                        break;
                    case Server.Asia:
                        if (AsiaGameList.Count > 1000)
                            AsiaGameList.Clear();
                        GameList = from k in gameList orderby k.Players descending select k.GameName;
                        foreach (string game in GameList)
                        {
                            if (!AsiaGameList.Contains(game))
                            {
                                AsiaGameList.Add(game);
                                return game;
                            }
                        }
                        break;
                }
            }
            return null;
        }

                                  

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