static void UsePoints()
{
try
{
var point = new Point(10, 20);
// point.move(new Point(40, 60));
point.move(null);
Console.WriteLine("pint is at ({0}, {1})", point.x, point.y);
point.move(100, 200);
Console.WriteLine("pint is at ({0}, {1})", point.x, point.y);
}
catch (Exception)
{
// throw;
Console.WriteLine("unexpecte error");
}
}