Passing NetworkCredential to HttpWebRequest in C# from ASP.Net Page

The NetworkCredentials are either extremely non-intuitive, or flaky, or both. Regardless, you can solve the issue by bypassing NetworkCredentials altogether and use this method (which I found, courtesy of mark.michaelis.net)

/* http://mark.michaelis.net/Blog/CallingWebServicesUsingBasicAuthentication.aspx */
byte[] credentialBuffer = new UTF8Encoding().GetBytes(username + ":" +password);
req.Headers["Authorization"] ="Basic " + Convert.ToBase64String(credentialBuffer);

So what you're doing is manually creating a header for your HttpWebRequest and inserting the content as it would appear in a Basic Authentication header. Works like a charm.

Microsoft Premier Support finally helped me solve this problem by using the CredentialCache class to add the Credentials and the "Basic" authorization:

NetworkCredential nc =
    new NetworkCredential(GetSetting("username"), GetSetting("password"));
CredentialCache cache = new CredentialCache();

cache.Add(requestUri, "Basic", nc);

HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(requestUri);