c# - Webclient / HttpWebRequest with Basic Authentication returns 404 not found for valid URL

Question

Edit: I wanted to come back to note that the problem wasn't on my end at all, but rather with with code on the other company's side.

I'm trying to pull up a page using Basic Authentication. I keep getting a 404 Page not found error. I can copy and paste my url into the browser and it works fine (if I'm not logged into their site already it pops up a credential box, otherwise it opens what I want it to open). I must be getting to the right place and authenticating, because I get a 401 (not authenticated error) if I intentially put in a bad username/password and I get an internal server error 500 if I pass it a bad parameter in the query string. I've tried using Webclient and HttpWebRequest both leading to the same 404 not found error.

With Webclient:

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);

With 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);

Answer 1

//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);