using System;

public class Program

{

    public static void Main()

    {

        Square s = new Square(10);

        Console.WriteLine("Square Length {0}",s.SideLength);    

        Console.WriteLine("Square Sides {0}",s.NoOfSides);

        Console.WriteLine("Square Perimeter {0}",s.GetPerimeter());

        Console.WriteLine("Square Area {0}",s.GetArea());

    }

}

​

public class ConcreteClass

{

    //automatic property

    public int NoOfSides {get;set;}

    //full property

    private int len;

    public int SideLength 

    {

        get { return len; } 

        set {

            len =  value; 

            }

    }

    public ConcreteClass(int ns,int len)

    {

        NoOfSides = ns;

        SideLength = len;

    }

    public double GetPerimeter()

    {

        return NoOfSides * SideLength;

    }

    public virtual double GetArea()

    {

        throw new NotImplementedException();

        //return 500;

    }

}

​

public class Square : ConcreteClass

{

​

    public Square(int length): base(4,length)

    {

    }

    //use new keyword to hide base class iheritance, not having this method will call the getArea method of base class and throw exception(in this case)

    public override double GetArea()

    {

    return SideLength * SideLength;

    }

​

}

​