title: enumerable group field using Linq?
body: <p>I've written a Linq sentence like this:</p>
  
  <pre><code>var fs = list
      .GroupBy(i =&gt;
          new { 
              X = i.X,
              Ps = i.Properties.Where(p =&gt; p.Key.Equals("m"))  &lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;
          }
      )
      .Select(g =&gt; g.Key });
  </code></pre>
  
  <p>Am I able to group by <code>IEnumerable.Where(...)</code> fields?</p>