There are a few but take a look at similar problem solved in VB, translation in C# is trivial.
http://forums.esri.com/thread.asp?c=93&f=992&t=92592
and also SDK is our Bible regarding ArcOjects.
http://resources.esri.com/help/9.3/ArcGISDesktop/dotnet/7467a056-cf74-4f86-bb14-33502d0e1033.htm
regards