using System;

using System.Collections.Generic;

using System.Linq;

public class Bar<T>

{

    private readonly T _value;

    public T Value() {

        return _value;

    }

    public Bar(T value) {

        _value = value;

    }

}

​

public abstract class Car

{

    public Ferrari Parent { get; set; }

}

​

public class Ferrari : Car

{

}

​

public class Lambo : Car

{

}

public class Program

{

    public static void Main(string[] args)

    {

        Car p1 = new Ferrari();

        Car p2 = new Lambo();

        Car p3 = new Lambo();

        p2.Parent = new Ferrari();

        List<Car> items = new List<Car>();

        items.Add(p1);

        items.Add(p2);

        items.Add(p3);

        Bar<Car> b = new Bar<Car>(null);

        List<Car> list2 = items.Where(item => item.Parent == b.Value()).ToList();

        bool z = null == b.Value();

        Console.WriteLine(list2.Count);

    }

}