As of WP 7.1 Mango "release", if one may call it, please see the WebBrowser Control Overview for Windows Phone. It has been recently updated a little bit, and it turns out that they actually have added some support for cookie-retrieval from the WebBrowser. On the bottom of the page you will find a tiny link GetCookies(WebBrowser) pointing to description of a new class: WebBrowserExtensions with this very handy method. Yes, this class has only that one single member. It's an extension method, I suppose no explanations needed on that.
I have not played with this method much, but it seems that this will allow you to access the very same thing as the JS trick: the cookieset for the current URL. It probably will not allow to set anything, nor to peek cookies for other URLs. Maybe if you play hard with the CookieContainer you will receive, but I doubt.
On the 7.0 release, I've been struggling quite hard to achieve "cookie transparency" for my App. Long story short, my app was doing some background HTTP requests, and also had a WebBrowser to show some online content -- and "it would be great" if both sources of connections would emit the same cookies to the server.. And guess what, my application had to make the first request, then let the browser navigate. With such requirements, there was virtually is no way to achieve consistency of the cookies - bah, even with the current new and glorious GetCookie method, I suppose it would be damn hard. So, to the point - it was possible, but needed to use some hidden API, that is present publicitly on the Phone, but is hidden in the SDK. The API is available the (public) class System.Net.Browser.WebRequestCreator, freely available. The quirk is: in the SDK this class has a single public static property "IWebRequestCreate ClientHttp" with a method "Create" that you can use to "factory" your "raw http" connections - in case you dont want to use the WebClient for some reason. On the phone, and on the emulator, there is a second public static property called "IWebRequestCreate BrowserHttp", easily returned by Reflection:
PropertyInfo brwhttp = typeof(System.Net.Browser.WebRequestCreator)
.GetProperty("BrowserHttp")
with this property, you will be able to obtain a "special" internal instance of IWebRequestCreate that is used internally by the WebBrowser. By opening your background HTTP requests with this class, you will get your cookies automatically set as if they were created/sent by the WebBrowser control, but in turn - you will NOT be able to modify http headers, userprovide http user authentication and neither do a few lowlevel things - because all that settings will be synced with the WebBrowser's data stored for current 'system user instance', if I'm allowed to call it as such on the single-user Phone device heh. The interoperation between connections and the WebBrowser works both ways - if your HTTP connection (created with use of the 'hidden property') receives any settings/cookies/etc -- then the WebBrowser will instantly notice them and update its own cache. No cookie/session loss on neither of the sides!
If you need to passively get cookies for your subsequent connections after some first WebBrowser navigation - please use the GetCookie or the JS way.
But if you need your code to be first, and then pass authz to the WebBrowser -- you will probably have to dig deeper and use the above.. It's been hidden, so please resort to the other means first!
..and don't ask me how did I found it or how much time it took :P
have a nice fun with it
//edit: I've just found out, that the BrowserHttp property is a normal Silverlight's way to access the Browser's connection factory, please see BrowserHttp. It seems that it is only has been hidden in the 'miniSilverlight' written for the WP7 platform!
