Windows Phone

WebAuthenticationBroker for Windows Phone Silverlight 8.x

In Windows Phone 8.1 both the Silverlight and Windows App programming models introduce the WebAuthenticationBroker class. This is inherited from “big” windows but with a change to reflect differences in the app model. Rather than operate as an asynchronous method within the context of your app there is instead an AuthenticateAndContinue method. This closes your app and launches the authentication window in a separate process, returning to your app upon completion. You will find that AuthenticateAsync will throw an exception even though the method is in intellisense and not marked as obsolete. You then need to hook the ContractActivated event of your application instance to determine the result when your application is relaunched. This flow is used not just by the WebAuthenticationBroker but also file pickers and other contract operations.

In Windows Phone 8.0 projects I built my own WebAuthenticationBroker to match the desktop API and with the release of Windows Phone 8.1 I tweaked the look slightly to match and released it as part of the Charming Apps for Windows Phone project. You’ll find this in NuGet here. You can then add OAuth with a couple of lines of code e.g.:-

WebAuthenticationResult result = await WebAuthenticationBroker.AuthenticateAsync(WebAuthenticationOptions.None, requestUri, callbackUri);
if (result.ResponseStatus == WebAuthenticationStatus.Success)
   // parse the token here (implementation specific)

The dialog displays the app name and uses as much space as possible for the web content:-


Some caveats – I’ve only used it with a couple of OAuth providers so I can’t guarantee it will support every variation. As with the Microsoft implementations you still have to do some manual parsing of the returned data to get your token. It doesn’t support WebAuthenticationOptions (other than None) and doesn’t read the HTML meta-tags Microsoft introduced to display a logo or background colour. It will however use the app logo and title as the built-in component does on 8.1.

While this does support 8.1 I would suggest that if you are starting a new project you use the built in component and ContractActivated event, if you want to target both 8.0 and 8.1 then you can use this component and the user experience is consistent with the built-in experience.


By Peter Foot

Microsoft Windows Development MVP