using System;

using System.Collections;

using System.Collections.Generic;

​

public interface IHasParts

{

    ICollection Parts { get; }

}

​

public abstract class HasParts<TCollectionType, TPartType> : IHasParts where TCollectionType : ICollection

{

    public TCollectionType Parts;

    ICollection IHasParts.Parts { get { return this.Parts; } }

}

​

public class CarPart

{

    //...

}

​

public class Car : HasParts<List<CarPart>, CarPart>

{

    protected void AddParts()

    {

        this.Parts.Add(new CarPart());

    }

}

​

public class Program

{

    public static void Main()

    {

        Car c = new Car() {

            Parts = new List<CarPart>() {new CarPart()

            }

        };

​

        object o = (object)c;

​

        int partsCount = ((IHasParts)o).Parts.Count;

        Console.WriteLine(partsCount);

    }

}