C# - Get Top Level Domain name from Url

#Url from Episerver:

  string siteUrl = (SiteDefinition.Current.SiteUrl).ToString().TrimEnd(new []{'/'});
                var topUrl = siteUrl.Substring((siteUrl.Length - 2), 2);
              

With Javascript:
function getTopDomain(h) {
            return h.substring(h.length,h.length-2);
        }