Questions every good NET developer should be able to answer

Question

Developers for.NET will soon be hired by my business. We deal with ASP.NET, Compact Framework, Windowsforms, and Web Services, among other.NET platforms. To gauge the applicants' level of experience, I'd like to build a list or library of excellent questions. I thus ask:

Which queries, in your opinion, should a competent.NET programmer be able to address?

I would also use it as a self-assessment tool to determine where my own deficiencies are (there are many...).

*UPDATE: We want to be clear that we're not just testing for.NET expertise and that general programming skills and problem-solving aptitudes are even more crucial to us.