title: Bind command to X-button of window title bar
body: <p>My WPF maintenance window have a toolbar with a button "Exit"; a CommandExit is bind with this button. The CommandExit perform some checks before exit.</p>
  
  <p>Now, if I click to close button of the window (x-button of title bar), this checks are ignored.</p>
  
  <p>How can I do to bind CommandExit to window x-button?</p>