static void Main(string[] args)
        {
            StructPixel sp;
            ClassPixel  cp;

            sp = new StructPixel(10, 20);
            cp = new ClassPixel(100, 200);
            movePixel(ref sp);
            movePixel(cp);
        }
 static void movePixel(ref StructPixel sp)
 {
     sp.x++;
     sp.y++;
 }