That said, if I was writing a GUI+database thing, which doesn't do a lot of substantial processing (more just Add/Edit/Delete buttons), I'd definately use C# over Haskell. Haskell can do this, but you are walking a relatively new path. On the other hand C# developers do this day in, day out, and the language is optimised towards it.
I agree with Neil here. I've been working with Haskell for a while and I wouldn't have the foggiest idea of how to start a GUI / Database project. After working with C# for about a week, I had a substantial GUI / Database program going for a company I interned with last summer. Haskell is good for a lot of things, and I'm sure somebody someday will show me that Haskell is even great for GUI/Database, but you should always use the right tool for the job, and for your job, I'd say C# is the right tool. Bryan Burgers