Border of Image

void currentImage_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            try
            {
                    currentImage=(Image)sender;
                    Border brdr = new Border();
                    brdr.BorderThickness = new Thickness(1);
                    brdr.BorderBrush = new SolidColorBrush(Colors.Gray);
                    brdr.Background = new SolidColorBrush(Colors.Red);
                    brdr.CornerRadius = new CornerRadius(5);
                    brdr.Child = currentImage;
                    currentImage.????????????????????????????????????????????
             }
            catch (Exception ex)
            {
                ;
            }
        }
 how can I Give border of the currentImage when Image is selected