Matthew Brindley, your code worked very good for some website I needed (with login), but I needed to change to HttpWebRequest and HttpWebResponse otherwise I get a 404 Bad Request from the remote server. Also I would like to share my workaround using your code, and is that I tried it to login to a website based on moodle, but it didn't work at your step "GETting the page behind the login form" because when successfully POSTing the login, the Header 'Set-Cookie' didn't return anything despite other websites does.
So I think this where we need to store cookies for next Requests, so I added this.
To the "POSTing to the login form" code block :
var cookies = new CookieContainer();
HttpWebRequest req = (HttpWebRequest)WebRequest.Create(formUrl);
req.CookieContainer = cookies;
And To the "GETting the page behind the login form" :
HttpWebRequest getRequest = (HttpWebRequest)WebRequest.Create(getUrl);
getRequest.CookieContainer = new CookieContainer();
getRequest.CookieContainer.Add(resp.Cookies);
getRequest.Headers.Add("Cookie", cookieHeader);
Doing this, lets me Log me in and get the source code of the "page behind login" (website based moodle) I know this is a vague use of the CookieContainer and HTTPCookies because we may ask first is there a previously set of cookies saved before sending the request to the server. This works without problem anyway, but here's a good info to read about WebRequest and WebResponse with sample projects and tutorial:
Retri
answered 2011-12-10T05:01:02.497