The following code shows me that cacheasbitmap is turning on and off like it is suppose to but, I never get to see it visually like I did in AS2. Is this a error or a change in actionscript?

package {
import flash.display.Sprite;
import flash.events.MouseEvent;

public class Bitmapascache extends Sprite
{
    private var isOn:Boolean=false;
    private var box:mainBox;
    public function Bitmapascache()
    {
            box  = new mainBox()
            box.addEventListener(MouseEvent.MOUSE_DOWN,click);

            this.addChild(box);
    }

    public function click(e:MouseEvent):void
    {
        trace("click :"+box.cacheAsBitmap);
        if(isOn){
            box.cacheAsBitmap = false;
            isOn = false;
        }
        else{
            box.cacheAsBitmap = true;   
            isOn = true;
        }
    }
}

}