How to read mac address of system

Question

Hi!!!!!
I have made a exe file of my C# project.....
can anyone tell me how can my application read the mac address of target{user} system.........Also how can It be valid only for 1 year i.e. how to add the code of subscription in my application that as user install my software then it should be valid for 1 yr only and no other person could install it on his system.......