An Error Occurred Setting Your User Cookie using Webclient

public class CookieAwareWebClient : WebClient

   
{
        private CookieContainer m_container = new CookieContainer();

        protected override WebRequest GetWebRequest(Uri address)
        {
            WebRequest request = base.GetWebRequest(address);
            if (request is HttpWebRequest)
            {
                (request as HttpWebRequest).CookieContainer = m_container;
            }
            return request;
        }
    }

CookieAwareWebClient client = new CookieAwareWebClient();

 string  page  =client.DownloadString(hdnSelectedLink.Value);