title: Why isn't there a Guid.IsNullOrEmpty() method
body: <p>This keeps me wondering why Guid in .NET does not have <code>IsNullOrEmpty()</code> method (where empty means all zeros)</p>
  
  <p>I need this at several places in my ASP.NET MVC code when writing the REST API.</p>
  
  <p>Or am I missing something because nobody on the Internet has asked for the same?</p>