i'm using asp.net with c# to create an online Exam ... one of the security stuff i wanna implement is that when the student is taking the exam he won't be able to switch to another window in his pc means the asp page has to be maximized and the student won't be able to resize it other important thing he can't use any of the keys on the keyboard to access the start menu or search his pc.

so how can i lock the screen on that page without letting it lose the focus until the student is done from his exam ..

please help me
thanks

You cannot make changes on envirioment of browser what is running your page ...

This is not possible.
You may develop something like timelimiting of an answer ...

Accessing client System is only through Scripting language ( ex : java script ) . Instead use timing .
For example give 30 second for each Question .If the time expires ( 30 sec over ) then it should go to next question , even though he hadn't answer to the last question . This mechanism is followed by many online test

answer fix timing is best answer, u cant fully control enviorment of client system even wih javascript

Dear friend, I think its very difficult task however i suggest you that one alternative:
implement SetFocus method to every page and then in javascript check that if this page is active if yes then nothing do and if not then do the session time out or redirect to any default error page says : your session has been expired.
Let me know if it is works.