WebRequest req = WebRequest.Create(formUrl.Trim());

public void LoginToUrl(string url,string username, string password )
{
    formUrl = url;
    formParams = string.Format("username={0}&password={1}", username,password);

    WebRequest req = WebRequest.Create(formUrl.Trim());//
    req.ContentType = "application/x-www-form-urlencoded";
    req.Method = "POST";
      bytes = Encoding.ASCII.GetBytes(formParams);
    req.ContentLength = bytes.Length;
    using (Stream os = req.GetRequestStream())
    {
        os.Write(bytes, 0, bytes.Length);
    }
    WebResponse resp = req.GetResponse();
    cookieHeader = resp.Headers["Set-cookie"];
}

Host=internetlogin1.cu.edu.ng

User-Agent=Mozilla/5.0 (Windows NT 10.0; WOW64; rv:37.0) Gecko/20100101 Firefox/37.0

Accept=text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8

Accept-Language=en-US,en;q=0.5

Accept-Encoding=gzip, deflate

Connection=keep-alive

Content-Type=application/x-www-form-urlencoded

Content-Length=49
POSTDATA=dst=&popup=true&username=13ck015373&password=F3NB

Uri serverUri = new Uri("http://url.com/sub/somethingService");
var webRequest = (HttpWebRequest)WebRequest.Create(serverUri);

var webRequest = (HttpWebRequest)WebRequest.Create("http://url.com/sub/somethingService");