title: How to enumerate all the registered sources for an EventLog
body: <p>If I select to filter the "Application" log in the EventLog viewer, I can see a lot of Sources registered with the "Application" log. How could I programmatically enumerate all these sources via C#? And it seems I cannot register my own evento source with "Application" and "System" log, why?</p>
  
  <p>BTW: The concept of "event source" is really confusing...</p>