source: binary-improvements/7dtd-server-fixes/src/PersistentData/Players.cs@ 327

using System;
using System.Collections.Generic;
using System.Text.RegularExpressions;

namespace AllocsFixes.PersistentData {
        [Serializable]
        public class Players {
                private readonly Dictionary<string, Player> players = new Dictionary<string, Player> (StringComparer.OrdinalIgnoreCase);

                public Player this [string steamId, bool create] {
                        get {
                                if (string.IsNullOrEmpty (steamId)) {
                                        return null;
                                }

                                if (players.ContainsKey (steamId)) {
                                        return players [steamId];
                                }

                                if (!create || steamId.Length != 17) {
                                        return null;
                                }

                                Log.Out ("Created new player entry for ID: " + steamId);
                                Player p = new Player (steamId);
                                players.Add (steamId, p);
                                return p;
                        }
                }

                public List<string> SteamIDs {
                        get { return new List<string> (players.Keys); }
                }

                public int Count {
                        get { return players.Count; }
                }

//              public Player GetPlayerByNameOrId (string _nameOrId, bool _ignoreColorCodes)
//              {
//                      string sid = GetSteamID (_nameOrId, _ignoreColorCodes);
//                      if (sid != null)
//                              return this [sid];
//                      else
//                              return null;
//              }

                public string GetSteamID (string _nameOrId, bool _ignoreColorCodes) {
                        if (_nameOrId == null || _nameOrId.Length == 0) {
                                return null;
                        }

                        long tempLong;
                        if (_nameOrId.Length == 17 && long.TryParse (_nameOrId, out tempLong)) {
                                return _nameOrId;
                        }

                        int entityId;
                        if (int.TryParse (_nameOrId, out entityId)) {
                                foreach (KeyValuePair<string, Player> kvp in players) {
                                        if (kvp.Value.IsOnline && kvp.Value.EntityID == entityId) {
                                                return kvp.Key;
                                        }
                                }
                        }

                        foreach (KeyValuePair<string, Player> kvp in players) {
                                string name = kvp.Value.Name;
                                if (_ignoreColorCodes) {
                                        name = Regex.Replace (name, "\\[[0-9a-fA-F]{6}\\]", "");
                                }

                                if (kvp.Value.IsOnline && name.EqualsCaseInsensitive (_nameOrId)) {
                                        return kvp.Key;
                                }
                        }

                        return null;
                }
        }
}