Definitely use C#.Net. Don't even think about visual basic.
If you ever get stuck just google "msdn c# <term>" and you will get loads of hits.
For example, I googled -> msdn c# rand
and I got this on the first hit ->
http://msdn.microsoft.com/en-us/library/system.random.aspxGood luck! Once you know one language, transitioning to another should be pretty easy.