具有基本身份验证的 Webclient / HttpWebRequest 返回 404 未找到有效 URL

编辑：我想回来指出问题根本不在我这边，而是与另一家公司的代码有关。

我正在尝试使用基本身份验证来打开页面。我不断收到 404 页面未找到错误。我可以将我的网址复制并粘贴到浏览器中，它工作正常（如果我尚未登录他们的网站，它会弹出一个凭据框，否则它会打开我想要打开的内容）。我必须到达正确的位置并进行身份验证，因为如果我故意输入错误的用户名/密码，我会收到 401（未经身份验证的错误），如果我在查询字符串中传递错误的参数，我会收到内部服务器错误 500 。我尝试过使用 Webclient 和 HttpWebRequest 都会导致相同的 404 未找到错误。

使用网络客户端：

string url = "MyValidURLwithQueryString";
WebClient client = new WebClient();
String userName = "myusername";
String passWord = "mypassword";
string credentials = Convert.ToBase64String(Encoding.ASCII.GetBytes(userName + ":" + passWord));
client.Headers[HttpRequestHeader.Authorization] = "Basic " + credentials;
var result = client.DownloadString(url);
Response.Write(result);

使用 HttpWebRequest

HttpWebRequest request = (HttpWebRequest)WebRequest.Create("MyValidURL");
string authInfo = "username:password";
authInfo = Convert.ToBase64String(Encoding.Default.GetBytes(authInfo));
request.Headers.Add("Authorization", "Basic " + authInfo);
request.Credentials = new NetworkCredential("username", "password");
request.Method = WebRequestMethods.Http.Get;
request.AllowAutoRedirect = true;
request.Proxy = null;
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
Stream stream = response.GetResponseStream();
StreamReader streamreader = new StreamReader(stream);
string s = streamreader.ReadToEnd();
Response.Write(s);

//BEWARE
//This works ONLY if the server returns 401 first
//The client DOES NOT send credentials on first request
//ONLY after a 401
client.Credentials = new NetworkCredential(userName, passWord); //doesnt work

//So use THIS instead to send credentials RIGHT AWAY
string credentials = Convert.ToBase64String(
    Encoding.ASCII.GetBytes(userName + ":" + password));
client.Headers[HttpRequestHeader.Authorization] = string.Format(
    "Basic {0}", credentials);