Sample Main method for pattern matching

Program.cs

static void Main()
{
  var r1 = new Rectangle(position: (200, 200), size: (200, 200));
  var e1 = new Ellipse(position: (80, 1400), size: (80, 140));
  var shapes = new Shape[]
  {
    r1,
    e1,
    new Circle((40, 60), 90),
    new CombinedShape(r1, e1)
  };

  foreach (var shape in shapes)
  {
    Console.WriteLine(M1(shape));
  }
}