title: Revit API How to make a external command run asynchrously?
body: <p>I have an External Command to create about 40 (or even more) Generic model
   in Revit. I want to make Revit run the command asynchronously to speed up the process according to this flow:</p>
  
  <p>load command -> run command -> load families -> <strong>generate family instances asynchronously</strong> -> end command.</p>
  
  <p>I 've read some ideas a bout make a modeless dialog to work around but it is not what I need. How can I do this?</p>