title: How enumerate all classes with custom class attribute?
body: <p>Question based on <a href="https://web.archive.org/web/20170228051218/https://msdn.microsoft.com/en-us/library/aa288454(VS.71).aspx" rel="noreferrer">MSDN example</a>.</p>
  
  <p>Let's say we have some C# classes with HelpAttribute in standalone desktop application. Is it possible to enumerate all classes with such attribute? Does it make sense to recognize classes this way? Custom attribute would be used to list possible menu options, selecting item will bring to screen instance of such class. Number of classes/items will grow slowly, but this way we can avoid enumerating them all elsewhere, I think.</p>