title: query list with linq lambda expressions
body: <p>How would I get participants that are in a list of counties?  I get the counties in var counties, then I want to get all of the participants that have a CountyOfParticipationId that is in the list of counties.</p>
  
  <pre><code>if (collaborationId != null)
  {
      var counties = (from c in db.CountyCollaborations
                      where c.CollaborationId == collaborationId
                      select c).ToList();
      participants = participants.Where(p =&gt; p.CountyOfParticipationId in counties);
  
  
  }
  </code></pre>