親が同じ場合に子供をリストする方法

これは私がタスクを達成するために見つけた最良の方法です：

using System;
using System.Collections.Generic;
using System.Collections;
using System.Linq;
using System.Text;
using System.Xml;
using System.Xml.Linq;
using System.IO;
using System.Diagnostics;
using System.Data;
namespace ConsoleApplication45
{
    class Program
    {
        static void Main(string[] args)
        {
            List<Business> companies = new List<Business>() {
                new Business() { name = "CompanyA",items = new List<Item>(){ new Item() { name = "Item1"}, new Item() { name = "Item2"}}},
                new Business() { name = "CompanyB", items = new List<Item>() { new Item() { name = "Item3"}, new Item() { name = "Item4"}}},
                new Business() { name = "CompanyA",items = new List<Item>(){ new Item() { name = "Item5"}, new Item() { name = "Item6"}}},
            };

            var groups = companies.GroupBy(x => x.name).Select(x => new { business = x.FirstOrDefault(), items = x.SelectMany(y => y.items) });
            List<Business> newCompanies = new List<Business>();
            foreach (var group in groups)
            {
                Business company = group.business;
                company.items = group.items.ToList();
                newCompanies.Add(company);
            }
        }
    }
    public class Business
    {
        public string name { get; set; }
        public List<Item> items { get; set; }
        public decimal taxrate { get; set; }
        public string month { get; set; }
    }
    public class Item
    {
        public string name { get;set;}
        public decimal price { get;set;}
        public decimal total { get;set;}
    }
}