using System;

​

public abstract class ClassA

{

    public virtual void MyFunction()

    {

        DoSomething();

        _MyFunction();

    }

    protected abstract void _MyFunction();

    protected void DoSomething() {

        Console.WriteLine("Do Something");

    }

}

​

public class ClassB : ClassA

{

    protected override void _MyFunction()

    {

        DoSomethingElse();

    }

    protected void DoSomethingElse() {

        Console.WriteLine("Do Something Else");

    }

}

​

​

public class Program

{

    public static void Main()

    {

        var b = new ClassB();

        b.MyFunction();

    }

}