using System;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        var c = new Container();

        Console.WriteLine(c.AAs.Count);

        Console.WriteLine(c.BBs[0].Invoices.GetType());

        Console.WriteLine(c.CCs[0].Invoices.GetType().GenericTypeArguments[0].Name);

    }

}

​

public class XXInvoice { }

public class XX<TInvoice> where TInvoice : XXInvoice

{

    public List<TInvoice> Invoices;

}

​

public class AAInvoice : XXInvoice {}

public class AA : XX<AAInvoice> { }

​

public class BBInvoice : XXInvoice {}

public class BB : XX<BBInvoice> { }

​

public class CCInvoice : XXInvoice {}

public class CC : XX<CCInvoice> { }

​

public class Container

{

    public List<AA> AAs = InitializeInvoice<AA, AAInvoice>();

    public List<BB> BBs = InitializeInvoice<BB, BBInvoice>();

    public List<CC> CCs = InitializeInvoice<CC, CCInvoice>();

​

    private static List<T> InitializeInvoice<T, TInvoice>()

        where T: XX<TInvoice>, new()

        where TInvoice : XXInvoice

    {

        return new List<T>

        {

            new T

            {

                Invoices = new List<TInvoice>()

            }

        };

    }

}