System.Net.HttpListener.AddChallenge C# (CSharp) Method

        private static void AddChallenge(ref ArrayList challenges, string challenge)
        {
            if (challenge != null)
            {
                challenge = challenge.Trim();
                if (challenge.Length > 0)
                {
                    if (NetEventSource.IsEnabled) NetEventSource.Info(null, "challenge:" + challenge);
                    if (challenges == null)
                    {
                        challenges = new ArrayList(4);
                    }
                    challenges.Add(challenge);
                }
            }
        }