title: Test if the Ctrl key is down using C#
body: <p>I have a form that the user can double click on with the mouse and it will do something. Now I want to be able to know if the user is also holding the <kbd>Ctrl</kbd> key down as the user double click on the form.</p>
  
  <p>How can I tell if the user is holding the <kbd>Ctrl</kbd> key down?</p>