title: Is it possible to use ref types in C# built-in Action<> delegate?
body: <p>C# has built-in delegates <code>Action&lt;&gt;</code> and <code>Func&lt;&gt;</code>. Is it possible to use 'ref' type parameters for this delegates? For example, this code:</p>
  
  <pre><code>public delegate void DTest( ref Guid a );
  public event DTest ETest;
  </code></pre>
  
  <p>Will compile. But if I use <code>Action&lt;&gt;</code>, it will not compile:</p>
  
  <pre><code>public event Action&lt; ref Guid &gt; ETest;
  </code></pre>
  
  <p>Any hints?</p>