protected function citylist_itemClickHandler(event:ListEvent):void
    {
        var data:City = citylist.selectedItem as City;
        navigateToURL(new URLRequest(data.url));

    }

<mx:List includeIn="data" x="28" y="10" width="312" height="255" id="citylist" dataProvider="{getCitysResult.lastResult}" labelField="city" itemClick="citylist_itemClickHandler(event)">
    </mx:List>