it varies. they may ask you about object orientation development, maybe some data access questions like SQL/OleDB
maybe asking you on how you pass variables, whats good practice/bad practice, how to improve good - being efficient such as using a StringBuilder class to create strings rather than using a standard string variable and appending to that.
they may also ask about properties (accessors) and why you should/shouldnt use them.
these maybe some of the questions.
How much experiance ie years, Projects - projects include schooling and such.
That other types of programming experiance do you have. JAVA, PHP, ASP, CGI, .......A good programmer or someone that has experiance with multiple languages. For me I was hired as VB programmer and did not have much VB experiance on 2005. But have lots of programming experiance in other languages. You have to think that if a person knows alot of other languages they might be able to pickup a language pretty quick. So multiple languages is a must - or a good indication that this person likes programming.
Hope that helps alittle more.