Serial key validation in C#

Question

serial key validation in C#.
I completed my project in C#.Net.
I Added the serial key in it.
at the time of installation it ask me for the key.
The key format is also given by me.
But i don't know how to validate that key.
please Give me some way that how to validate that key.
Now my key is validated by the visual studio or i don't know who and how the key's validation is done.
But i want to do the validation by my own way.so is it possible?and how? please help.
lot of Thanks.