title: Merge Lists and return only duplicates
body: <p>Say I've got two lists:</p>
  
  <pre><code>List&lt;string&gt;foo=new List&lt;string&gt;();
  List&lt;string&gt;bar=new List&lt;string&gt;();
  </code></pre>
  
  <p>I want to merge these two lists and return another list with only the duplicates in the both.
  <br/>So if I have:</p>
  
  <pre><code>//pseudocode
  foo={"baz","lemons","somethingelse"}
  bar={"what","another","baz","somethingelse","kitten"}
  </code></pre>
  
  <p>I want it to return a new List:</p>
  
  <pre><code>//pseudocode
  dupes={"baz","somethingelse"}
  </code></pre>
  
  <p>I think using LINQ will be the best shot. However, I haven't quite figured that since I have poor LINQ experience.<br/></p>