using System;

public class Program

{

    public static void Main()

    {

        var instance = new A();

        instance.Method1();

        var instance2 = new B();

        instance2.Method1();

    }

    public class A

    {

        public virtual void Method1()

            {

            Console.WriteLine("Hello Heaven");

            }

    }

​

    public class B : A

    {

        public override void Method1() // Generates CS0506.

            {

            Console.WriteLine("Hello Earth");

            }

    }

}

​