title: What is the proper way to send an HTTP 404 response from an ASP.NET MVC action?
body: <p>If given the route:</p>
  
  <p><strong>{FeedName}/{ItemPermalink}</strong></p>
  
  <p>ex: /Blog/Hello-World</p>
  
  <p>If the item doesn't exist, I want to return a 404. What is the right way to do this in ASP.NET MVC?</p>