using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main(string[] args)

    {

        var invoice = new Invoice

        {

            InvoiceID = 1,

            tInvoicePayments = new List<InvoicePayment>

            {

                new InvoicePayment

                {

                    InvoiceID = 1,

                    Active = true,

                    tPayment = new tPayment

                    {

                        PaymentID =1,

                        tInvoicePayments = new List<InvoicePayment>

                        {

                            new InvoicePayment { InvoiceID = 1, Active = true },

                            new InvoicePayment { InvoiceID = 2, Active = true },

                            new InvoicePayment { InvoiceID = 3, Active = true },

                            new InvoicePayment { InvoiceID = 3, Active = false }

                        }

                    }

                },

                new InvoicePayment

                {

                    InvoiceID = 1,

                    Active = true,

                    tPayment = new tPayment

                    {

                        PaymentID = 2,

                        tInvoicePayments = new List<InvoicePayment>

                        {

                            new InvoicePayment { InvoiceID = 1, Active = true },

                            new InvoicePayment { InvoiceID = 1, Active = true },

                        }

                    }

                }

            }

        };

​

        var payments = invoice.tInvoicePayments.Select(x => x.tPayment);

        var paymentsToDelete = payments

            .Where(x => x.tInvoicePayments.All(y => y.Active && y.InvoiceID == invoice.InvoiceID))

            .ToList();

​

        foreach (var tPayment in paymentsToDelete)

        {

            Console.WriteLine(tPayment.PaymentID);

        }

​

        var newPaymentsToDelete = invoice.tInvoicePayments.Any(x => !x.Active)

            ? null

            : invoice.tInvoicePayments.Select(x => x.tPayment);

​

        foreach (var tPayment in paymentsToDelete)

        {

            Console.WriteLine(tPayment.PaymentID);

        }

​

​

        Console.ReadLine();

    }

​

}

​

class Invoice

{

    public int InvoiceID { get; set; }

​

    public List<InvoicePayment> tInvoicePayments { get; set; }

}

​

class InvoicePayment

{

    public int InvoiceID { get; set; }

​

    public tPayment tPayment { get; set; }

​

    public bool Active { get; set; }

}

​

class tPayment

{

    public int PaymentID { get; set; }

    public List<InvoicePayment> tInvoicePayments { get; set; }

}