How to AutoDetect/Use IE proxy settings in .net HttpWebRequest

HttpWebRequest will actually use the IE proxy settings by default.

If you don't want to use them, you have to specifically override the .Proxy proprty to either null (no proxy), or the proxy settings of you choice.

 HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://news.bbc.co.uk");
 //request.Proxy = null; // uncomment this to bypass the default (IE) proxy settings
 HttpWebResponse response = (HttpWebResponse)request.GetResponse();

 Console.WriteLine("Done - press return");
 Console.ReadLine();

I was getting a very similar situation where the HttpWebRequest wasn't picking up the correct proxy details by default and setting the UseDefaultCredentials didn't work either. Forcing the settings in code however worked a treat:

IWebProxy proxy = myWebRequest.Proxy;
if (proxy != null) {
    string proxyuri = proxy.GetProxy(myWebRequest.RequestUri).ToString();
    myWebRequest.UseDefaultCredentials = true;
    myWebRequest.Proxy = new WebProxy(proxyuri, false);
    myWebRequest.Proxy.Credentials = System.Net.CredentialCache.DefaultCredentials;
}

and because this uses the default credentials it should not ask the user for their details.

Note that this is a duplicate of my answer posted here for a very similar problem: Proxy Basic Authentication in C#: HTTP 407 error

For people having problems with getting this to play nice with ISA server, you might try to set up proxy in the following manner:

IWebProxy webProxy = WebRequest.DefaultWebProxy;
webProxy.Credentials = CredentialCache.DefaultNetworkCredentials;
myRequest.Proxy = webProxy;