title: How to know user has clicked "X" or the "Close" button?
body: <p>In MSDN I found <code>CloseReason.UserClosing</code> to know that the user had decided to close the form
  but I guess it is the same for both clicking the X button or clicking the close button.
  So how can I differentiate between these two in my code?</p>
  
  <p>Thanks all.</p>