Usually the first thing they will do is sit you in front of a workstation and tell you to solve 10 problems using Visual Studio and Microsoft SQL Server Management Studio. The code is mostly in VB.NET and ASP.
This is a practical exam but don't sweat it - you'll have access to Google and all you really need to know are "Response.Write", "Response.Flush" and "Response.End" to debug the little puzzles (most of which are coding typos). You don't even have to finish all ten, they just want to make sure you can eventually reason your way out of a wet paper bag.
The truth is the company is pretty desperate for developers right now after churning and burning through the local community. Oh, and if a friend who works there is recommending you for the job, get them to front the down payment on your new car because the referral bonus is that insane.