Uri baseUri = new Uri(url); //main URL
                    Uri myUri = new Uri(baseUri, strRef); //strRef is new found link
                    //domain = baseUri.Host;
                    domain = baseUri.Host.Replace("www.", string.Empty).Replace("http://", string.Empty).Replace("https://", string.Empty).Trim();

                    string domain2=myUri.Host.Replace("www.", string.Empty).Replace("http://", string.Empty).Replace("https://", string.Empty).Trim();

                    strRef = myUri.ToString();
                    if (domain2==(domain) )
                    { //DO STUFF }

string url = "http://www.xxx.co.uk";
            string strRef = "http://www.news.xxx.co.uk";

            Uri baseUri = new Uri(url); //main URL
            Uri myUri = new Uri(baseUri, strRef); //strRef is new found link
            var domain = baseUri.Host;
            domain = baseUri.Host.Replace("www.", string.Empty).Replace("http://", string.Empty).Replace("https://", string.Empty).Trim();

            //hrere is solution

            string domain2 = GetDomainName(strRef);

            strRef = myUri.ToString();
            if (domain2 == (domain))
            { //DO STUFF

            }



   private static string GetDomainName(string url)
        {
            string domain = new Uri(url).DnsSafeHost.ToLower();
            var tokens = domain.Split('.');
            if (tokens.Length > 2)
            {
                //Add only second level exceptions to the < 3 rule here
                string[] exceptions = { "info", "firm", "name", "com", "biz", "gen", "ltd", "web", "net", "pro", "org" };
                var validTokens = 2 + ((tokens[tokens.Length - 2].Length < 3 || exceptions.Contains(tokens[tokens.Length - 2])) ? 1 : 0);
                domain = string.Join(".", tokens, tokens.Length - validTokens, validTokens);
            }
            return domain;
        }