title: Conditional operator doesn't work with two types that inherit the same base type
body: <p>How come the conditional operator (<code>?:</code>) doesn't work when used with two types that inherit from a single base type?</p>
  
  <p>The example I have is:</p>
  
  <pre><code>ActionResult foo = (someCondition)? 
                        RedirectToAction("Foo","Bar") :
                        Redirect(someUrl);
  </code></pre>
  
  <p>Where the long form works fine:</p>
  
  <pre><code>ActionResult foo;
  
  if(someCondition)
  {
    foo = RedirectToAction("Foo","Bar");
  }
  else
  {
    foo = Redirect(someUrl);
  }
  </code></pre>
  
  <p>Both return types, <code>RedirectToRouteResult</code>  and <code>RedirectResult</code>, inherit from <code>ActionResult</code>.</p>