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

        private void ArchiveBySequence(string fileName, string pattern)
        {
            FileNameTemplate fileTemplate = new FileNameTemplate(Path.GetFileName(pattern));
            int trailerLength = fileTemplate.Template.Length - fileTemplate.EndAt;
            string fileNameMask = fileTemplate.ReplacePattern("*");

            string dirName = Path.GetDirectoryName(Path.GetFullPath(pattern));
            int nextNumber = -1;
            int minNumber = -1;

            var number2Name = new Dictionary<int, string>();

            try
            {
#if SILVERLIGHT && !WINDOWS_PHONE
                foreach (string s in Directory.EnumerateFiles(dirName, fileNameMask))
#else
                foreach (string s in Directory.GetFiles(dirName, fileNameMask))
#endif
                {
                    string baseName = Path.GetFileName(s);
                    string number = baseName.Substring(fileTemplate.BeginAt, baseName.Length - trailerLength - fileTemplate.BeginAt);
                    int num;

                    try
                    {
                        num = Convert.ToInt32(number, CultureInfo.InvariantCulture);
                    }
                    catch (FormatException)
                    {
                        continue;
                    }

                    nextNumber = Math.Max(nextNumber, num);
                    minNumber = minNumber != -1 ? Math.Min(minNumber, num) : num;

                    number2Name[num] = s;
                }

                nextNumber++;
            }
            catch (DirectoryNotFoundException)
            {
                Directory.CreateDirectory(dirName);
                nextNumber = 0;
            }

            if (minNumber != -1 && ShouldDeleteOldArchives())
            {
                int minNumberToKeep = nextNumber - this.MaxArchiveFiles + 1;
                for (int i = minNumber; i < minNumberToKeep; ++i)
                {
                    string s;

                    if (number2Name.TryGetValue(i, out s))
                    {
                        if (!DeleteOldArchiveFile(s))
                            break;
                    }
                }
            }

            string newFileName = ReplaceNumberPattern(pattern, nextNumber);
            ArchiveFile(fileName, newFileName);
        }