NLog.Targets.FileTarget.ArchiveByDateAndSequence C# (CSharp) Method

        private void ArchiveByDateAndSequence(string fileName, string pattern, LogEventInfo logEvent)
        {
            string baseNamePattern = Path.GetFileName(pattern);

            if (string.IsNullOrEmpty(baseNamePattern))
            {
                return;
            }

            string dirName = Path.GetDirectoryName(Path.GetFullPath(pattern));
            if (string.IsNullOrEmpty(dirName))
            {
                return;
            }

            FileNameTemplate fileTemplate = new FileNameTemplate(baseNamePattern);
            string fileNameMask = fileTemplate.ReplacePattern("*");
            string dateFormat = GetArchiveDateFormatString(this.ArchiveDateFormat);

            int minSequenceLength = fileTemplate.EndAt - fileTemplate.BeginAt - 2;
            int nextSequenceNumber;
            DateTime archiveDate = GetArchiveDate(fileName, logEvent);
            List<string> archiveFileNames;
            if (Directory.Exists(dirName))
            {
                List<DateAndSequenceArchive> archives = FindDateAndSequenceArchives(dirName, fileName, fileNameMask, minSequenceLength, dateFormat, fileTemplate)
                    .ToList();

                // Find out the next sequence number among existing archives having the same date part as the current date.
                int? lastSequenceNumber = archives
                    .Where(a => a.HasSameFormattedDate(archiveDate))
                    .Max(a => (int?)a.Sequence);
                nextSequenceNumber = (int)(lastSequenceNumber != null ? lastSequenceNumber + 1 : 0);

                archiveFileNames = archives
                    .OrderBy(a => a.Date)
                    .ThenBy(a => a.Sequence)
                    .Select(a => a.FileName)
                    .ToList();
            }
            else
            {
                Directory.CreateDirectory(dirName);
                nextSequenceNumber = 0;
                archiveFileNames = new List<string>();
            }

            string paddedSequence = nextSequenceNumber.ToString().PadLeft(minSequenceLength, '0');
            string archiveFileNameWithoutPath = fileNameMask.Replace("*",
                string.Format("{0}.{1}", archiveDate.ToString(dateFormat), paddedSequence));
            string archiveFileName = Path.Combine(dirName, archiveFileNameWithoutPath);

            ArchiveFile(fileName, archiveFileName);
            archiveFileNames.Add(archiveFileName);
            EnsureArchiveCount(archiveFileNames);
        }