WebClient generates (401) Unauthorized error

Question

I have the following code running in a windows service:

WebClient webClient = new WebClient();
webClient.Credentials = new NetworkCredential("me", "12345", "evilcorp.com");
webClient.DownloadFile(downloadUrl, filePath);

Each time, I get the following exception

{"The remote server returned an error: (401) Unauthorized."}

With the following inner exception:

{"The function requested is not supported"}

I know for sure the credentials are valid, in fact, if I go to downloadUrl in my web browser and put in my credentials as evilcorp.com\me with password 12345, it downloads fine.

What is weird though is that if I specify my credentials as [email protected] with 12345, it appears to fail.

Is there a way to format credentials?

Answer 1

Apparently the OS you are running on matters, as the default encryption has changed between OSes. This blog has more details: http://ferozedaud.blogspot.com/2009/10/ntlm-auth-fails-with.html

This has apparently also been discussed on stackoverflow here: http://stackoverflow.com/questions/1443617/407-authentication-required-no-challenge-sent/1482442#1482442

I would suggest read the blog first as the distilled knowledge is there.

Answer 2

According to the msdn docs the exception could be because the method has been called simultaneously on multiple threads. The DownloadFile method also requires a completely qualified URL such as http://evilcorp.com/.