Does a Windows 8 Modern-UI app need a main page?
I'd like to implement a File Picker Contract provider so that other applications can open files from my web service. Other than providing the UI in response to File Open, there's no need for the app to have its own interface - no need for its own main page that shows when launched from the Start screen. In fact, it'd probably be best if the app didn't even show itself on the Start screen.
Is this possible and are there samples or documentation I can follow for this? Thanks, I'm having a hard time finding the answer through the doc pages I've seen so far.
I don't think your app will pass certification if you create something that doesn't have an interface. In fact, as far as I know, you need to show a UI within a certain amount of time for the app to not be suspended/shut-down by the OS / runtime.
In other words - yes an app needs a main page / UI.
Are you sure you really need a Metro / Modern UI app at all in your situation? Perhaps a desktop app with appropriate file associations set up should do?