How to logout of after logging in with facebook login in ASP.Net

Hello,

I read the article http://www.aspsnippets.com/Articles/Login-with-FaceBook-account-in-ASPNet-Website.aspx. It works well for me. But I want to know how to logout. This article has been written by 

Mudassar Ahmed Khan. I wish him to  answer. Please answer as it is urgent.