using System;

public class Program

{

    public static void Main()

    {

        var test = new BaseClass();

        // Expect false

        Console.WriteLine(test.Abool);

        var test2 = new DerivedClass();

        // Expect false

        Console.WriteLine(test2.Abool);

        test2.Abool = true;

        // Expect true

        Console.WriteLine(test2.Abool);

        // Expect false

        OutputValue(test);

        // Expect true

        OutputValue(test2);

    }

    private static void OutputValue(BaseClass obj)

    {

        Console.WriteLine(obj.Abool);

    }

}

public class BaseClass

{

    private bool? _aBool;

    public bool Abool {

        get {

            if (_aBool.HasValue) {

                return _aBool.Value;

            }

            _aBool = false;

            return _aBool.Value;

        }

    }

}

​

public class DerivedClass : BaseClass

{

    private bool _derivedBool = false;

    public new bool Abool

    {

        get

        {

            return _derivedBool;

        }

        set

        {

            _derivedBool = value;

        }

    }

}

​