title: What's the Comparer<T> class for?
body: <p>What purpose does the <code>Comparer&lt;T&gt;</code> class serve if the type that you specify already implements <code>IComparable</code>?  </p>
  
  <p>If I specify Comparer.Default, and Customer already implements IComparable, then why would I use the Comparer class?</p>