title: Drag and Drop - How to get the DragSource on the DragStart event
body: <p>When I start a drag operation I would like to be able to highlight the possible valid Drop objects. For this I need to know when the drag operation starts and which items are being dragged. I am trying to do this using the dragStart, but the event.dragSource is null on this event.</p>
  
  <p>I have this list:</p>
  
  <pre><code>&lt;s:List
      width="100%"
      height="100%"
      id="productsListing" 
      dragEnabled="true"
      dataProvider="{products}"
      dragStart="dragStartHandler(event);"
      dragComplete="dragCompleteHandler(event);"
      itemRenderer="views.productListed" /&gt;
  </code></pre>
  
  <p>And I have the listener as:</p>
  
  <pre><code>public function dragStartHandler(event:DragEvent):void {
      var itemsVector:Vector.&lt;Object&gt; = event.dragSource.dataForFormat('itemsByIndex') as Vector.&lt;Object&gt;;
      //Verify Items
      //Highlight appropriated dropZones
  }
  </code></pre>
  
  <p>Anyone have a good sugestion how to overcome this?</p>