title: how to close a window from a different process
body: <p>I have a c# application which I want to instruct to shutdown nicely, from a different process.
  I also want to be able to ask it to open its main window.
  I have a reference to its main window handle.</p>
  
  <p>I know I can do it using elaborate schemes such as remoting or WCF.
  the question is can I do it using simpler mechanisms such as window messages, or the OnClose event handlers of the window in the c# application</p>