title: Convert List of objects to List of interfaces
body: <p>if i have objectA that implements ISomeInterface</p>
  
  <p>why can't i do this:</p>
  
  <pre><code>List&lt;objectA&gt; list = (some list of objectAs . . .)
  
  List&lt;ISomeInterface&gt; interfaceList = new List&lt;ISomeInterface&gt;(list);
  </code></pre>
  
  <p>why can't i stick in list into the interfaceList constructor ?  Is there any workaround?</p>