title: Handle task time in asp.net
body: <p>In an online examination system how could i handle exam elapsed and remaining time.<br>
  At the first i managed to solve this problem by using javascript to setup a client side timer in the exam web page at the moment the student come in the exam page and notify server by using ajax in every interval of that timer; so i could update exam duration of current student.<br>
  Everything seems OK but the problem becomes apparent when a curious student disables javascript in Browser during exam and re enable it before clicking submit button. hence timer stops and browser could not send ajax requests to the server.<br>
  What's the best way to handle this problem ?<br>
  Thanks in advance.</p>