If you want to kick the re-usability and overall sophistication of your LOB .NET app (including Windows Store) up a notch, consider the Enterprise Library from Microsoft's Patterns and Practices team. They recently launched an update that you can read about here: Enterprise Library.
I'll steal P&P's blurb about it:
The Microsoft Enterprise Library is a collection of reusable software components (application blocks) designed to assist software developers with common enterprise development cross-cutting concerns (such as logging, validation, data access, exception handling, and many others). Application blocks are a type of guidance; they are provided as source code, test cases, and documentation that can be used "as is," extended, or modified by developers to use on complex, enterprise-level line-of-business development projects.