title: wpf - have dll callback notify mainwindow
body: <p>I have a 3rd party dll that I am including in a C# WPF project with Dllimport directives.
  I have a static c# function that they call as a callback when a certain hardware event occurs.</p>
  
  <p>I would like to accomplish what an old school PostMessage would accomplish. Just notify my mainwindow that the callback occurred. I know I could just get my window and cast and call the mainwindow's function directly but that seems a little flaky. I like the old async PostMessage pattern. Perhaps my question is more about loosely coupling a couple of components in the app.</p>
  
  <p>Should I just invoke a command? </p>