title: Determine the relative complement of two IEnumerable<T> sets in .NET
body: <p>Is there an easy way to get the <a href="http://en.wikipedia.org/wiki/Complement_(set_theory)" rel="noreferrer">relative complement</a> of two sets?  Perhaps using LINQ?</p>
  
  <p>I have to find the relative compliment of a set A relative to B.  Both A and B are of type <code>HashSet&lt;T&gt;</code> but I think the algorithm could be made more general (<code>IEnumerable&lt;T&gt;</code> or even <code>ISet&lt;T&gt;</code>)?</p>
  
  <p>I could use a solution in either VB.NET or C#.</p>