NLog.Targets.FileTarget.DynamicFileArchive.ExtractArchiveNumberFromFileName C# (CSharp) Method

            private static int ExtractArchiveNumberFromFileName(string archiveFileName)
            {
                archiveFileName = Path.GetFileName(archiveFileName);
                int lastDotIdx = archiveFileName.LastIndexOf('.');
                if (lastDotIdx == -1)
                    return 0;

                int previousToLastDotIdx = archiveFileName.LastIndexOf('.', lastDotIdx - 1);
                string numberPart = previousToLastDotIdx == -1 ? archiveFileName.Substring(lastDotIdx + 1) : archiveFileName.Substring(previousToLastDotIdx + 1, lastDotIdx - previousToLastDotIdx - 1);

                int archiveNumber;
                return Int32.TryParse(numberPart, out archiveNumber) ? archiveNumber : 0;
            }
        }