How to determine who is running my C# code

Question

My C#.NET application just needs to know who is running it. (That is, who has logged in to the w2k domain through the PC system on which my C# applicatoin is running.) I've seen a lot of articles on how to perform exotic work utilizing Active Directory. Can anyone offer a hint about how to do this simple thing? BIG THANK YOU to anyone who can offer a solution!!!