title: ListBox.SelectedItem is null notification
body: <p>I need to track current selected item in ListBox to turn off some other controls on the form when selected item become null. I try to use SelectedIndexChanged event, but it not raise when selected item is null.</p>
  
  <p>Can you please advise something?</p>
  
  <p>UPDATE: Selected item becomes null because i set new DataSource value with empty collection. May be it's a reason of my problem?</p>
  
  <p>I need to explain. ListBox represent collection of items from database. When user add/edit/delete some item, I refresh listbox by calling this method: </p>
  
  <pre><code>private void RefreshList()
  {
       lbParts.DataSource = this.database.Fetch&lt;part&gt;(string.Empty);
  }
  </code></pre>
  
  <p>It fetched all items from database, convert it to <code>List&lt;part&gt;</code> collection and set as ListBox DataSource.</p>