title: where t : multiple classes
body: <pre><code>List&lt;T&gt; Foo&lt;T&gt;(Ilist list) 
  where T : ??
  </code></pre>
  
  <p>is there any way to enforce T to be<br>
  one of few classes ?</p>
  
  <p>eventually i want to do a switch on T..</p>
  
  <p>thanks.</p>