MissionPlanner.srtm.getListing C# (CSharp) Method

        static List<string> getListing(string url)
        {
            string name = new Uri(url).AbsolutePath;

            name = Path.GetFileName(name.TrimEnd('/'));

            List<string> list = new List<string>();

            if (File.Exists(datadirectory + Path.DirectorySeparatorChar + name))
            {
                var fi = new FileInfo(datadirectory + Path.DirectorySeparatorChar + name);
                if (fi.Length > 0 && fi.LastWriteTime.AddDays(7) > DateTime.Now)
                {
                    using (StreamReader sr = new StreamReader(datadirectory + Path.DirectorySeparatorChar + name))
                    {
                        while (!sr.EndOfStream)
                        {
                            list.Add(sr.ReadLine());
                        }

                        sr.Close();
                    }
                    return list;
                }
            }

            try
            {
                log.Info("srtm req " + url);

                WebRequest req = HttpWebRequest.Create(url);

                using (WebResponse res = req.GetResponse())
                using (StreamReader resstream = new StreamReader(res.GetResponseStream()))
                {

                    string data = resstream.ReadToEnd();

                    Regex regex = new Regex("href=\"([^\"]+)\"", RegexOptions.IgnoreCase);
                    if (regex.IsMatch(data))
                    {
                        MatchCollection matchs = regex.Matches(data);
                        for (int i = 0; i < matchs.Count; i++)
                        {
                            if (matchs[i].Groups[1].Value.ToString().Contains(".."))
                                continue;
                            if (matchs[i].Groups[1].Value.ToString().Contains("http"))
                                continue;
                            if (matchs[i].Groups[1].Value.ToString().EndsWith("/srtm/version2_1/"))
                                continue;

                            list.Add(url.TrimEnd(new char[] {'/', '\\'}) + "/" + matchs[i].Groups[1].Value.ToString());
                        }
                    }
                }

                using (StreamWriter sw = new StreamWriter(datadirectory + Path.DirectorySeparatorChar + name))
                {
                    list.ForEach(x =>
                    {
                        sw.WriteLine((string) x);
                    });

                    if (name.Equals("README.txt") || name.Equals("Region_definition.jpg"))
                        sw.Write(" ");

                    sw.Close();
                }
            }
            catch (WebException ex)
            {
                log.Error(ex);
                throw;
            }

            return list;
        }