Click here to Skip to main content
13,196,126 members (53,285 online)
Click here to Skip to main content
Add your own
alternative version


14 bookmarked
Posted 13 Mar 2008

Authenticating with a proxy in WPF

, 13 Mar 2008
Rate this:
Please Sign up or sign in to vote.
Resolution of a nasty problem with WPF HttpRequests via a proxy.


The basic story is that I had some code that went off to a timestamp server using HttpWebRequest and worked fine in .NET 2.0. Then, I had to use it with .NET 3.0, and got the error:

(407) Proxy Authentication Required.

Now, I already had all the code to add a proxy to the request, and the very same code worked in .NET 2.0, so it was a bit of a mystery. At the time of writing, WPF is still pretty new, and so there is not a lot of documentation. Hence, a week of wasted time began, and once I had the solution, I figured I should document it here to save others.

For the reference information that helped me tie down the problem, you can visit:

Using the code

It turns out that .NET 3.0 uses a custom CredentialPolicy for HttpWebRequest calls. This is apparently a security enhancement for XBAP applications to stop sending passwords to remote proxies. As a result, if .NET 3.0 feels that your proxy is not a local machine, then it will not send any authentication information. This piggy-backs on another annoying Microsoft issue in that it is really poor at deciding which machines are local and which aren't. Hence, it often refuses to pass the credentials even when the proxy is a local machine (as was the case for me).

The solution is to supply your own CredentialPolicy that allows the username/password information to be sent to the proxy. This is done by creating a class that implements the ICredentialPolicy interface and returns true to the ShouldSendCredential method. Then, using an instance of this class, set AuthenticationManager.CredentialPolicy. Some demonstration code is included below.

class ProxyCredentials : ICredentialPolicy {
    bool ICredentialPolicy.ShouldSendCredential(Uri challengeUri, WebRequest request, 
             NetworkCredential credential, IAuthenticationModule authenticationModule) {
        return true;
class DemoRequest {
    static DemoRequest() {
        AuthenticationManager.CredentialPolicy =  new ProxyCredentials();
    public DoRequest() {
        HttpWebRequest httprequest = 
        IWebProxy proxy = WebRequest.GetSystemWebProxy();
        proxy.Credentials = System.Net.CredentialCache.DefaultCredentials;
        httprequest.Proxy = proxy;
        httprequest.PreAuthenticate = true;


This article, along with any associated source code and files, is licensed under The BSD License


About the Author

Paul Coldrey
Architect Lumient Pty Ltd
Australia Australia
No Biography provided

You may also be interested in...

Comments and Discussions

QuestionSecurity Exception Pin
mhargreaves9-Feb-11 1:34
membermhargreaves9-Feb-11 1:34 

General General    News News    Suggestion Suggestion    Question Question    Bug Bug    Answer Answer    Joke Joke    Praise Praise    Rant Rant    Admin Admin   

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.

Permalink | Advertise | Privacy | Terms of Use | Mobile
Web03 | 2.8.171019.1 | Last Updated 13 Mar 2008
Article Copyright 2008 by Paul Coldrey
Everything else Copyright © CodeProject, 1999-2017
Layout: fixed | fluid