using System;

​

namespace Example

{

    abstract class PrivateFoo

    {

        private int _directionX = -1;

​

        protected int DirectionX

        {

          get

          {

            return _directionX;

          }

​

          set

          {

            _directionX = value;

​

            ExtraWork();

          }

        }

​

        protected abstract void ExtraWork();

​

        protected abstract void Start();

    }

​

    class Foo : PrivateFoo

    {

​

        protected override void ExtraWork()

        {

        }

​

        protected override void Start()

        {

            this.DirectionX = 0;     //Compiles

            _directionX = 0;         //Does not compile

        }

    }

​

}

public class Program

{

    public static void Main()

    {

    }

}