title: Object reference not set to instance of an object
body: <p>I have a web form which works fine until you keep on working on it. But if you leave it for 20 mins, on submit button click it gives the following error</p>
  
  <p><img src="https://i.stack.imgur.com/ktGo4.jpg" alt="enter image description here">
  Error</p>
  
  <p>It seems to me the page request object gets NULL but exactly cant reach to the issue.
  I have tried to increase the session timeout at IIS but it did not help.</p>
  
  <p>Please help me to know the root cause for it.</p>
  
  <p>Thanks all</p>