InvoiceList Class

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Indexers
{
    public class InvoiceList
    {
        private List<Invoice> invoices;

        public InvoiceList()
        {
            invoices = new List<Invoice>();
        }

        public void Add(Invoice invoice)
        {
            invoices.Add(invoice);
        }

        public void Add(string number, string description, int quantity, decimal price)
        {
            Invoice i = new Invoice(number, description, quantity, price);
            invoices.Add(i);
        }

        public void Remove(Invoice invoice)
        {
            invoices.Remove(invoice);
        }

        public void Remove(int i)
        {
           invoices.RemoveAt(i);
        }
        public Invoice this[int i]
        {

            get
            {
                if (i < 0 || i > invoices.Count)
                {
                    throw new ArgumentException("Invalid index");
                }
                return invoices[i];
            }

            set { invoices[i] = value; }
        }

        public Invoice this[string desc]
        {
            get
            {
                foreach (Invoice invoice in invoices)
                {
                    if (invoice.Description.Equals(desc))
                    {
                        return invoice;
                    }
                }

                return null;

            }


        }


    }




}