title: how to fetch an item from an observable collection by index
body: <p>Why does this not work?  It throws an index out of range exception.  The item doesn't have on object in the third index, but I'm trying to check for that.  How else do I check for an empty index?</p>
  
  <pre><code>if (MyBusinessObject.MyObservableCollection[2] != null)
  {
      doSomething();
  }
  </code></pre>