title: Confirmation when closing WPF window with 'X' button or ESC-key
body: <p>How can I request confirmation when closing WPF window in desktop application with click 'X' button or by pressing ESC-key?<br/>
  I would like to make it with a minimum of code.<br/>
  Similar issue is <a href="https://stackoverflow.com/questions/14395301/confirmation-when-closing-window-with-x-button-with-mvvm-light">here</a> but on MVVM Light and there is too much code.</p>