System.Net.WebClient fails weirdly

Question

I am trying to download some data from the reporting services instance on our TFS server.
Given that the code should run on a computer that is not domain-joined, I figured that I would set the credentials myself. No luck, got a HTTP 401 Unauthorized back. Ok, so I hooked up Fiddler to see what was happening.

But that's when I got Heisenberged - the call now went through without a hitch. So the authentication goes through with Fiddler connected, but fails without it. Is the Webclient broken or am I missing something profound here?

private void ThisWorksWhenDomainJoined()
    {
        WebClient wc = new WebClient();
        wc.Credentials = CredentialCache.DefaultNetworkCredentials;
        wc.DownloadString("http://teamfoundationserver/reports/........");  //Works
    }

    private void ThisDoesntWork()
    {
        WebClient wc = new WebClient();
        wc.Credentials = new NetworkCredential("username", "password", "domain");
        wc.DownloadString("http://teamfoundationserver/reports/........");  //blows up wih HTTP 401
    }

+1 for using the heisenberg uncertaintly principle as a verb, never heard that one before! — Robert Venables
– Robert Venables, Commented Apr 26, 2009 at 23:06

Robert Vuković · Accepted Answer · 2009-11-29 10:42:22Z

4

Take a look at this link:
HTTP Authorization and .NET WebRequest, WebClient Classes

I had the same problem as you. I have only added one line and it started to work. Try this

private void ThisDoesntWork()
    {
        WebClient wc = new WebClient();
        wc.Credentials = new NetworkCredential("username", "password", "domain");
        //After adding the headers it started to work !
        wc.Headers.Add(HttpRequestHeader.UserAgent, "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1)");
        wc.DownloadString("http://teamfoundationserver/reports/........");  //blows up wih HTTP 401
    }

answered Nov 29, 2009 at 10:42

Robert Vuković

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Comments

JP Alioto · Accepted Answer · 2009-06-16 16:15:49Z

2

Try this ...

var credCache = new CredentialCache();
credCache.Add(new Uri("http://teamfoundationserver/reports/........""),
                      "Basic", 
                      new NetworkCredential("username", "password", "DOMAIN"));
wc.Credentials = credCache;

If that does not work, try replacing "Basic" with "Negotiate".

answered Jun 16, 2009 at 16:15

JP Alioto

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travis · Accepted Answer · 2009-06-16 16:22:40Z

1

What happens when you use this?

wc.Credentials = CredentialCache.DefaultCredentials;

Also, are you sure you have the correct username, password and domain?

Also: I wonder if Fiddler is changing around some unicode characters when .net breaks them or something like that. If your user/pass/domain has unicode, try escaping it out like "\u2638" instead of "☺".

edited Jun 16, 2009 at 16:22

answered Jun 16, 2009 at 16:07

travis

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1 Comment

travis Over a year ago

When working through a similar issue with a coworker just now we determined that fiddler was accessing the web service with your local credentials, where as the code in an Asp.Net app would use the asp.net user's credentials, which most likely don't have permissions.

Guy Starbuck · Accepted Answer · 2011-12-08 19:19:50Z

1

I was able to get around this error by using a CredentialCache object, as follows:

WebClient wc = new WebClient();
CredentialCache credCache = new CredentialCache();
credCache.Add(new Uri("http://mydomain.com/"), "Basic",
new NetworkCredential("username", "password"));

wc.Credentials = credCache;

wc.DownloadString(queryString));

answered Dec 8, 2011 at 19:19

Guy Starbuck

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