using System;

using System.Collections.ObjectModel;

​

public class InventoryItem

{

    public string Name { get; set; }

}

​

public class SuperInventoryItem : InventoryItem { }

​

public abstract class InventoryItemAbstractFactory<T> where T : InventoryItem

{

    public abstract T Create();

}

​

public class InventoryItemFactory : InventoryItemAbstractFactory<InventoryItem>

{

    public override InventoryItem Create() => new InventoryItem();

}

​

public class SuperInventoryItemFactory : InventoryItemAbstractFactory<SuperInventoryItem>

{

    public override SuperInventoryItem Create() => new SuperInventoryItem();

}

​

public class Inventory<T> where T : InventoryItem

{

    private readonly ObservableCollection<T> _inventory = new ObservableCollection<T>();

    private readonly InventoryItemAbstractFactory<T> _factory;

    public Inventory(InventoryItemAbstractFactory<T> factory) => _factory = factory;

    public void Add() => _inventory.Add(_factory.Create());

    public int Count => _inventory.Count;

}

​

public class Program

{

    public static void Main()

    {

        var c1 = new Inventory<InventoryItem>(new InventoryItemFactory());

        c1.Add();

        c1.Add();

​

        var c2 = new Inventory<SuperInventoryItem>(new SuperInventoryItemFactory());

        c2.Add();

        c2.Add();

​

        Console.WriteLine(c1.Count);

        Console.WriteLine(c2.Count);

    }

}