C# 7 pattern matching with the switch statement and type patterns with a filter

Program.cs

static string M1(Shape shape)
{
  switch (shape)
  {
    case Shape s when s.Size.height > 100:
      return $"large shape with size {s.Size} at position {s.Position}";
    case Ellipse e:
      return $"Ellipse with size {e.Size} at position {e.Position}";
    case Rectangle r:
      return $"Rectangle with size {r.Size} at position {r.Position}";
    default:
      return "another shape";                    
  }
}