Webclient ：：凭据未经授权

Question

                using (System.Net.WebClient webClient = new System.Net.WebClient())
            {
                try
                {
                    string USER = "123";
                    string PASS = "123";
                    var client = new WebClient();
                    client.Credentials = new NetworkCredential(USER, PASS);
                    htmlString = webClient.DownloadString(url);
                }

我的凭据有问题，我将其用于装载程序，但这始终表示401。