捕捉Silverlight程序全屏显示时候按ESC退出全屏显示

App.Current.Host.Content.FullScreenChanged+= new xxxxx

例子：

App.Current.Host.Content.FullScreenChanged += FullScreenChanged;

private void FullScreenChanged(object sender, EventArgs handler)
{
if (Application.Current.Host.Content.IsFullScreen)
{
TextBlock tb = LayoutRoot.FindName("txt_fullscreen") as TextBlock;
tb.Text = "退出全屏";
}
else
{
TextBlock tb = LayoutRoot.FindName("txt_fullscreen") as TextBlock;
tb.Text = "全屏";
}
}