C#.NET appl licensing

Question

I'm developing a C#.NET bussiness applicationand I'm starting to think about how I would handle licensing the fetures  prospective purchasers. By licensing, I mean the mechanics of trying to prevent my appl from being used by those who haven't purchased it, not the software license (i.e., Apache, Gnu, etc), provide demo version (ex. for 30 Days). Just some mechanism that gives me decent protection without making the customer jump through hoops or gnash their teeth.

Do you have any experience  with appl licensing?