development – Getting Links from an internal web page

I have an internal company’s web page and I need to extract a link from that page
what I tried is

using (var client = new System.Net.WebClient())
            {                    
                string pattern = @"(<a.*?>.*?</a>)";

                MatchCollection hreflist;

                string Url = client.DownloadString("https://collaborate.citi.net/docs/DOC-908807");                

                hreflist = Regex.Matches(Url, pattern);

                Console.WriteLine("Total number of links in Url: " + hreflist.Count + "nn");

But this code doesn’t seems to work here.