错过饼干;了1/3.我以为这是自动处理的，为什么事情不正常工作

有一种cookie不出现的趋势。我完全复制小提琴手，它应该是一个简单的任务，因为它是自动处理的。为什么我没有得到正确的cookie检索?

public class HTTP : WebClient
{
    public HTTP()
        : this(new CookieContainer())
    { }
    public HTTP(CookieContainer c)
    {
        CookieContainer = c;
    }
    public CookieContainer CookieContainer { get; set; }
    protected override WebRequest GetWebRequest(Uri address)
    {
        WebRequest request = base.GetWebRequest(address);
        var castRequest = request as HttpWebRequest;
        if (castRequest != null)
        {
            castRequest.CookieContainer = CookieContainer;
            castRequest.Accept = "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8";
            castRequest.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.22 (KHTML, like Gecko) Chrome/25.0.1364.172 Safari/537.22";
        }
        return request;
    }
} 

public void checkUrl()
{
CookieContainer cookieJar = new CookieContainer();
HTTP client = new HTTP(cookieJar);
string responseData = client.DownloadString(url);
       responseData = client.UploadString(url, loginData);
rtb.Text = responseData;
}