using System;

public class Program

{

    public static void Main()

    {

        var rect = new Rectangle { Height = 10, Length = 5 };

        var area = CalculateAreaSwitchStatement(rect);

        Console.WriteLine($"Area = {area}");

    }

    static double CalculateAreaSwitchStatement(object obj)

    {

        switch (obj)

        {

            case null:

                throw new ArgumentNullException(nameof(obj));

​

            case Square { Side: 0 }:

            case Circle { Radius: 0 }:

            case Rectangle { Length: 0 }:

            case Rectangle { Height: 0 }:

            case Triangle { Base: 0 }:

            case Triangle { Height: 0 }:

                return 0;

​

            case Square { Side: var s }:

                return s * s;

​

            case Circle { Radius: var r }:

                return r * r * Math.PI;

​

            case Rectangle { Length: var l, Height: var h }:

                return l * h;

​

            case Triangle { Base: var b, Height: var h}:

                return b * h / 2;

​

            default:

                throw new NotSupportedException();

        }

    }

​

}

​

# region Classes

​

public class Square

{

    public double Side { get; set; }

}

​

public class Circle

{

    public double Radius { get; set; }

}

​

public class Rectangle

{

    public double Length { get; set; }

    public double Height { get; set; }

}

​

public class Triangle

{

    public double Base { get; set; }

    public double Height { get; set; }

}

​

#endregion