source: binary-improvements/CoppisAdditions/src/Commands/ListPlayersFriends.cs@ 285

using System;
using System.Collections.Generic;
using System.Reflection;

namespace CoppisAdditions.CustomCommands
{
        public class ListPlayersFriends : ConsoleCmdAbstract
        {
                public override string GetDescription ()
                {
                        return "list friends of a single player or all players";
                }

                public override string GetHelp ()
                {
                        return "Usage:\n" +
                        "  1. lpf <steam id / player name / entity id>" +
                        "  2. lpf (to list all players friends)";
                }

                public override string[] GetCommands ()
                {
                        return new string[] { "listplayerfriends", "lpf" };
                }

                public override void Execute (List<string> _params, CommandSenderInfo _senderInfo)
                {
                        try {
                                if (_params.Count > 1) {
                                        SdtdConsole.Instance.Output ("Usage: listplayerfriends <entityid|playername|steamid> or listplayerfriends");
                                } else {
                                        if (_params.Count == 0) {
                                                foreach (string steamid in GameManager.Instance.persistentPlayers.Players.Keys) {
                                                        PrintFriendsOfPlayer (steamid);
                                                }
                                        } else {
                                                string steamid = null;

                                                ClientInfo ci = ConsoleHelper.ParseParamIdOrName (_params [0]);
                                                if (ci != null) {
                                                        steamid = ci.playerId;
                                                }

                                                if (steamid == null) {
                                                        if (ConsoleHelper.ParseParamSteamIdValid (_params [0])) {
                                                                steamid = _params [0];
                                                        }
                                                }

                                                if (steamid == null) {
                                                        SdtdConsole.Instance.Output ("Playername or entity/steamid id not found.");
                                                        return;
                                                }

                                                PrintFriendsOfPlayer (steamid);
                                        }
                                }
                        } catch (Exception e) {
                                Log.Out ("Error in ListPlayersFriends.Run: " + e);
                        }
                }

                private void PrintFriendsOfPlayer (string _steamid) {
                        PersistentPlayerData data = GameManager.Instance.persistentPlayers.GetPlayerData (_steamid);
                        string friends = "";
                        if (data != null && data.ACL != null) {
                                foreach (string friend in data.ACL) {
                                        if (!string.IsNullOrEmpty (friend)) {
                                                if (!friends.Equals ("")) {
                                                        friends += ",";
                                                }
                                                friends += friend;
                                        }
                                }
                        }
                        SdtdConsole.Instance.Output ("FriendsOf id=" + _steamid + ", friends=" + friends);
                }

        }
}