获取windows8的屏幕大小和改变事件

CoreWindow cw = CoreWindow.GetForCurrentThread();
_pagesize = new Size(cw.Bounds.Width, cw.Bounds.Height);
 cw.SizeChanged += cw_SizeChanged;

        async void cw_SizeChanged(CoreWindow sender, WindowSizeChangedEventArgs args)
        {

           //

        }