使用WebClient通过Login访问受保护的页面

Question

我正在尝试访问受登录表单保护的页面。我已经检查了SO中的主题，我发现了WebClient的这个扩展，它使用了cookie：

public class CookieAwareWebClient : WebClient
{
    public CookieAwareWebClient()
    {
        this.CookieContainer = new CookieContainer();
    }

    public CookieContainer CookieContainer { get; private set; }

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

在互联网的帮助下，我提出了一些代码：

using (var webClient = new CookieAwareWebClient())
        {
            try
            {
                NameValueCollection collection = new NameValueCollection
                {
                    {"UserName", userName},
                    {"Password", password}
                };

                webClient.UploadValues("https://judge.softuni.bg/Account/Login", "POST", collection);


                string result = webClient.DownloadString("https://judge.softuni.bg/Contests/Compete/Results/Simple/104");

            }
            catch (WebException webException)
            {
                MessageBox.Show(webException.Status.ToString());
            }
        }

最后在“结果”字符串中我有一个带有表单操作的登录页面，如果我登录，它会将我重定向到想要的页面。任何想法我做错了什么？