Many companies have a web proxy that allows employees to access the Internet, while at the same time preventing outsiders from accessing the company’s internal network. The problem is that to create an application that accesses the Internet from within your company, you must first connect to your proxy and then send information through it, rather than directly out to an Internet web server.
In order to
get a HttpWebRequest
successfully through a
specific proxy server, we need to set up a
WebProxy
object with the settings to validate our
specific request to a given proxy. Since this function is generic for
any request, we create the AddProxyInfoToRequest
method:
public static HttpWebRequest AddProxyInfoToRequest(HttpWebRequest httpRequest, string proxyUri, string proxyID, string proxyPwd, string proxyDomain) { if(httpRequest != null) { // create the proxy object WebProxy proxyInfo = new WebProxy( ); // add the address of the proxy server to use proxyInfo.Address = new Uri(proxyUri); // tell it to bypass the proxy server for local addresses proxyInfo.BypassProxyOnLocal = true; // add any credential information to present to the proxy server proxyInfo.Credentials = new NetworkCredential(proxyID, proxyPwd, proxyDomain); // assign the proxy information to the request httpRequest.Proxy = proxyInfo; } // return the request return httpRequest; }
If all requests are going to go through the same proxy, you can use
the static Select
method on the
GlobalProxySelection
class to set up the proxy
settings for all WebRequests
, like so:
Uri proxyURI = new Uri("http://webproxy:80"); GlobalProxySelection.Select = new WebProxy(proxyURI);
AddProxyInfoToRequest
takes the URI of the proxy
and creates a Uri
object, which is used to
construct the WebProxy
object. The
WebProxy
object is set to bypass the proxy for
local addresses and then the credential information is used to create
a
NetworkCredential
object. The NetworkCredential
object represents
the authentication information necessary for the request to succeed
at this proxy and is assigned to the
WebProxy.Credentials
property. Once the
WebProxy
object is completed, it is assigned to
the Proxy
property of the
HttpWebRequest
and the request is ready to be
submitted.