Inheritance in C#

using System;

namespace Inheritance

{

    interface I1

    {

        void Fun();

    }

    public abstract class A

    {

        // Implemented function can also be marked as virtual

        public virtual void Fun()

        {

            Console.WriteLine("I1::Fun()");

        }

        public abstract void Fun1();

        public virtual void Fun2()

        {

            Console.WriteLine("C1::Fun()");

        }

    }

    public class C1 : A

    {

        // Overriding abstract function of class A

        public override void Fun1()

        {

            Console.WriteLine("C1::Fun1()");

        }

        // Overriding virtual function of class A

        public override void Fun2()

        {

            Console.WriteLine("C1::Fun2()");

        }

    }

    public class C2 : C1

    {

        // Overriding virtual function of class A

        public override void Fun()

        {

            Console.WriteLine("C2::Fun()");

        }

        // Overriding abstract function of class A

        public override void Fun1()

        {

            Console.WriteLine("C2::Fun1()");

        }

        // Overriding virtual function of class A

        public override void Fun2()

        {

            Console.WriteLine("C2::Fun2()");

        }

    }

    class Program

    {

        static void Main(string[] args)

        {

            Console.ReadKey();

        }

    }

}