登录后Htmlagilitypack

我想解析一些像facebook这样的html网站，
例如(www.facebook.com/somePage)
如果我想将此链接粘贴到我的资源管理器，它会重定向我首先登录我的帐户。所以我不看那个页面。所以我不能使用Htmlagilitypack来获得响应。
那么我怎样才能首先登录网站programmaticaly（不使用webbrowser控件）然后调用该facebook页面并获得响应并使用Htmlagility包进行解析。我知道如何使用HtmlAgility包并且我知道使用Httprequest设置cookie我使用以下代码来设置cookie但是之后如何解析somePage

CookieCollection cookies = new CookieCollection();
        try
        {
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create("https://www.facebook.com");
            request.CookieContainer = new CookieContainer();
            request.CookieContainer.Add(cookies);
            //Get the response from the server and save the cookies from the first request..
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            cookies = response.Cookies;
            response.Close();
        }
        catch (WebException)
        {
            MessageBox.Show("error");
        }

        string getUrl = "https://www.facebook.com/login.php?login_attempt=1";
        string postData = String.Format("email={0}&pass={1}", "xxxx@hotmail.com", "xxxxx");
        HttpWebRequest getRequest = (HttpWebRequest)WebRequest.Create(getUrl);
        getRequest.CookieContainer = new CookieContainer();
        getRequest.CookieContainer.Add(cookies); //recover cookies First request
        getRequest.Method = WebRequestMethods.Http.Post;
        getRequest.UserAgent = "Mozilla/5.0 (Windows NT 6.1) AppleWebKit/535.2 (KHTML, like Gecko) Chrome/15.0.874.121 Safari/535.2";
        getRequest.AllowWriteStreamBuffering = true;
        getRequest.ProtocolVersion = HttpVersion.Version11;
        getRequest.AllowAutoRedirect = true;
        getRequest.ContentType = "application/x-www-form-urlencoded";

        byte[] byteArray = Encoding.ASCII.GetBytes(postData);
        getRequest.ContentLength = byteArray.Length;
        Stream newStream = getRequest.GetRequestStream(); //open connection
        newStream.Write(byteArray, 0, byteArray.Length); // Send the data.
        newStream.Close();
        //How I parse (www.facebook.com/somePage) here?
       HtmlAgilityPack.HtmlDocument doc = new HtmlAgilityPack.HtmlDocument();
       HttpWebResponse getResponse = (HttpWebResponse)getRequest.GetResponse();
       using (StreamReader sr = new StreamReader(getResponse.GetResponseStream(), Encoding.GetEncoding("windows-1251")))
        {

            doc.LoadHtml(sr.ReadToEnd());

        }

        foreach (HtmlNode link in doc.DocumentNode.SelectNodes("//a[@href]"))
        {
            listBox1.Items.Add(link.InnerHtml);
        }