using System;

public class Program

{

    public static void Main()

    {

        B obj = new B();

        string values = obj.sayHello();

        Console.WriteLine(values);

    }

}

​

public abstract class A {

    public string sayHi() { return "hi"; } // a method with code in it

    public abstract string sayHello();  // no implementation

}

​

public class B 

   : A

{

    // must implement, since it is not abstract

    public override string sayHello() { return "Hello from B"; }

}