using System;

using System.IO;

​

public abstract class Figure

{

    public double Height;

    public double Width;

    public abstract double Area();

    public virtual void Save()

    {

        //save the object to a file

        using (Stream stream = File.Open("saveFile.bin", FileMode.OpenOrCreate))

        {

        //BinaryFormatter formatter = new BinaryFormatter();

        //formatter.Serialize(stream, this);

        }

    }

}

​

public class Rect : Figure

{

    public Rect(double Height, double Width)

    {

        base.Height = Height;

        base.Width = Width;

    }

​

    public override double Area()

    {

        return (Height * Width);

    }

}

​

public class Square : Figure

{

    public Square(double dim)

    {

        base.Height = dim;

        base.Width = 0;

    }

​

    public override double Area()

    {

        return (Height * Height);

    }

}

​

public class Circle : Figure

{

    public Circle(double radius)

    {

        base.Height = radius;

        base.Width = 0;

    }

​

    public override double Area()

    {

        return (Height * Height * Math.PI);

    }

​

    public override void Save()

    {

    //throw new Exception("Circle cannot be saved!");

    }

}

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        Figure[] figs = new Figure[]{new Rect(2, 10), new Square(2), new Circle(5)};

        foreach (Figure f in figs)

        {

            Console.WriteLine(f.Area());

            f.Save();

        }

    }

}