AppMetrics.LogEvent.GetDataFilePath C# (CSharp) Method

        private static string GetDataFilePath(string applicationKey, string sessionId)
        {
            var basePath = SiteConfig.DataStoragePath;
            var dataRootPath = Path.Combine(basePath, applicationKey);
            if (!dataRootPath.StartsWith(basePath)) // block malicious application keys
                throw new ArgumentException(dataRootPath);

            if (!Directory.Exists(dataRootPath))
                Directory.CreateDirectory(dataRootPath);

            var filesMask = string.Format("*.{0}.txt", sessionId);
            var files = Directory.GetFiles(dataRootPath, filesMask);
            if (files.Length > 0)
            {
                if (files.Length != 1)
                    throw new ApplicationException(string.Format("Too much data files for session {0}", sessionId));
                return files[0];
            }
            else
            {
                var time = DateTime.UtcNow;
                var filePath = Const.FormatFilePath(dataRootPath, sessionId, time);
                return filePath;
            }
        }