how to detect zoom change in Microsoft Bing Maps

Question

Try the following:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
   <head>
      <title>Event view change start</title>
      <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
      <script type="text/javascript" src="http://ecn.dev.virtualearth.net/mapcontrol/mapcontrol.ashx?v=7.0"></script>

      <script type="text/javascript">
      var map, lastZoomLevel = 0;

      function getMap()
      {
        map = new Microsoft.Maps.Map(document.getElementById('myMap'), {credentials: 'Your Bing Maps Key'});

        lastZoomLevel = map.getZoom();
        Microsoft.Maps.Events.addHandler(map, 'viewchangeend', viewChanged);
      }

      function viewChanged(e)
      {
         if(lastZoomLevel != map.getZoom()){
            lastZoomLevel = map.getZoom();
            alert("Map Zoomed");
         }
      }
      </script>
   </head>
   <body onload="getMap();">
      <div id='myMap' style="; width:400px; height:400px;"></div>
   </body>
</html>