C# windows app and ASP.NET Web app sharing database

Question

I'm creating a library system project. I want it to be half web-base and half windows application. The web-base is for library users to register, search and reserve books online, and the windows application is for librarian to generate reports and other basic library works. Im almost done creating windows application but my problem is how can I share my database between two application? do you have any suggestion how can I implement this?