I have already created an application that implement and then manages the database access, validation, auth, authorization and repository pattern, while the unit testing(I can't use the integrated unit testing of visual studio because I have the express visual studio and then I should use Nunit) TDD and mobile support (What do you mean by the mobile support? What should I study to implement this?)

Also, for create an application that implements all this, would be fine an application that manages a library? or whatelse would be better for implement all this?

Very Thanks