Today the BCL Team Blog addressed the issue of code reuse: Porting existing .NET code to Metro style apps
"One of the things we know people want to do is reuse existing .NET code but due to the constraints on Metro style apps it is not possible to directly reuse existing .NET class libraries nor is it always possible to simply recompile existing code. We realize this is going to be a pain point for many current .NET developers so we are working on a guide at the .NET for Metro style apps overview page which will assist developers in translating their existing .NET skill set into the Metro style apps world.”
Bringing existing managed code into Metro style apps" by Daniel Plaisted is a recommended resource.
Daniel ports a windows phone app to a Metro app. Most of presentation is mainly about porting the UI.
Some slides from the presentation:
Getting the pictures from a local folder.
There is no database access.