C# - IPv4 - Adresse ermitteln

private string GetPublicIPv4()
        {
            try
            {
                string url = "http://checkip.dyndns.org";
                System.Net.WebRequest req = System.Net.WebRequest.Create(url);
                System.Net.WebResponse resp = req.GetResponse();
                System.IO.StreamReader sr = new System.IO.StreamReader(resp.GetResponseStream());
                string response = sr.ReadToEnd().Trim();
                string[] a = response.Split(':');
                string a2 = a[1].Substring(1);
                string[] a3 = a2.Split('<');
                string a4 = a3[0];
                return a4;
            }
            catch (Exception)
            {
                return null;
            }
        }