C#でのニコ動ログイン(動く)

gistfile1.cs

public bool DeepLogin()
{
    bool login = false;//ログイン成否

    HttpWebRequest req = WebRequest.CreateHttp(new Uri(deepLoginUrl, UriKind.Absolute));
    req.Method = "POST";
    req.ContentType = "application/x-www-form-urlencoded";
    req.CookieContainer = App.ViewModel.UserSetting.cc;
    using (StreamWriter sw = new StreamWriter(req.GetRequestStreamAsync().GetAwaiter().GetResult()))
    {
        sw.WriteAsync(string.Format("mail={0}&password={1}", App.ViewModel.UserSetting.UserID, App.ViewModel.UserSetting.UserPass)).GetAwaiter().GetResult();
        sw.FlushAsync().GetAwaiter().GetResult();
        sw.Dispose();
    }

    HttpWebResponse res = req.GetResponseAsync().GetAwaiter().GetResult() as HttpWebResponse;
    if (res != null && res.StatusCode == HttpStatusCode.OK)
    {
        if (res.ResponseUri.Host != "secure.nicovideo.jp")
            login = true;
    }

    return login;
}