设置应用程序的背景图片：

private void image1_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)        {            SetAppBackground("/ChangeBackground;component/Images/Lighthouse.png");        }        private static void SetAppBackground(string imageName)        {            var app = Application.Current as App;            if (app == null)                return;            var imageBrush = new ImageBrush            {                ImageSource = new BitmapImage(new Uri(imageName, UriKind.Relative))            };            app.RootFrame.Background = imageBrush;        }        private void image2_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)        {            SetAppBackground("/ChangeBackground;component/Images/Tulips.jpg");        }