Get the root domain of the current domain name

1 /// <summary> 2 /// obtain the root domain of the current domain name 3 /// </Summary> 4 /// <Param name = "url"> domain name address </param> 5 // <returns> </returns> 6 public static string rootdomain (string URL) 7 {8 If (! URL. startswith ("http ://")&&! URL. startswith ("https: //") 9 {10 url = "http: //" + URL; 11} 12 13 var uri = new uri (URL ); 14 string rootdomain; 15 switch (URI. hostnametype) 16 {17 case urihostnametype. DNS: 18 {19 if (URI. isloopback) 20 {21 rootdomain = Uri. host; 22} 23 else24 {25 string host = Uri. host; 26 var hosts = host. split ('. '); 27 rootdomain = hosts. length = 2? HOST: string. format ("{0 }. {1} ", hosts [1], hosts [2]); 28} 29} 30 break; 31 default: 32 rootdomain = Uri. host; 33 break; 34} 35 return rootdomain; 36}

When searching for such problems on the internet, regular expressions are generally used, and several domain name suffixes are fixed, for example. CN ,. com ,. net, so I wrote this method according to my work needs.
For reference.

Get the root domain of the current domain name