title: LINQ Determine if a property on an object in a collection exists in a different collection
body: <p>Say I have a collection of Person objects - </p>
  
  <pre><code>public class Person
  {
    public string Firstname { get; set; }
    public string Surname { get; set; }
  }
  </code></pre>
  
  <p>Now let's say I have a different collection, holding the surnames of the families I've invited to my party - </p>
  
  <pre><code>var guestlist = new List&lt;string&gt; {"Stark", "Wayne"};
  </code></pre>
  
  <p>How can I use linq (preferrably lamba based, but this doesn't matter too much) to only pull out members of the Stark or Wayne family? ie. I want to end up with another (third) collection, not just an indication that my first collection contains a Wayne or Stark family member.</p>