If the aplication is inactive 2 or 3 minutes it must automatically logout.(may be using timer control)

Question

The application is built using wpf and C# in (.net 3.5), in this  the application should automatically logout if it is inactive for few minutes.  i think one way is to use timer control and no ideas about other ways to do this task , if you know the concept and code for this using timercontrol or any other way, please guide me.