例如：http://www.google.co.uk，应该返回google.co.uk，http://www.test.googlepages.com,应该返回googlepages.com

我的程序如下，拿出来讨论下，写的比较弱智，必须预先知道所有的域名后缀。
请大家告诉我好的方法：

private string GetDomain(string url)
        {
            string host;
            Uri uri;
            try
            {

                uri = new Uri(url);
                host = uri.Host + " ";
            }
            catch
            {
                return "";
            }

            string[] BeReplacedStrs = new string[] { ".com.cn", ".edu.cn", ".net.cn", ".org.cn", ".co.jp", ".gov.cn", ".co.uk", "ac.cn", ".edu", ".tv", ".info", ".com", ".ac", ".ag", ".am", ".at", ".be", ".biz", ".bz", ".cc", ".cn", ".com", ".de", ".es", ".eu", ".fm", ".gs", ".hk", ".in", ".info", ".io", ".it", ".jp", ".la", ".md", ".ms", ".name", ".net", ".nl", ".nu", ".org", ".pl", ".ru", ".sc", ".se", ".sg", ".sh", ".tc", ".tk", ".tv", ".tw", ".us", ".co", ".uk", ".vc", ".vg", ".ws", ".il", ".li", ".nz" };

            foreach (string oneBeReplacedStr in BeReplacedStrs)
            {
                string BeReplacedStr = oneBeReplacedStr + " ";
                if (host.IndexOf(BeReplacedStr) != -1)
                {
                    host = host.Replace(BeReplacedStr, string.Empty);
                    break;
                }
            }

            int dotIndex = host.LastIndexOf(".");

           host = uri.Host.Substring(dotIndex + 1);
            return host;
        }
谢谢了！