title: What is Rhino.Mocks.Function
body: <p>Rhino Mocks adds two overloaded Stub methods to System.Object.  One is <code>Stub&lt;T&gt;(Action&lt;T&gt;)</code>  the other is <code>Stub&lt;T, R&gt;(Function&lt;T, R&gt;)</code></p>
  
  <p>What (if any) are the differences between <code>Rhino.Mocks.Function&lt;T, R&gt;</code> and <code>System.Func&lt;T, R&gt;</code>  They both behave the same, but I doubt Ayende would have gone through the trouble to make a new type that did the same thing as a built-in one that already existed.  </p>