public static double ComputeArea(object shape) => shape switch { Square s => s.Side * s.Side, Circle c => c.Radius * c.Radius * Math.PI,

public static double ComputeArea(object shape) => shape switch { Square s => s.Side * s.Side, Circle c => c.Radius * c.Radius * Math.PI, Rectangle r => r.Height * r.Length, _ => throw new ArgumentException( message: "shape is not recognized", paramName: nameof(shape)); }