Full join, C# - rextester

Language: Layout:

using System;
using System.Collections.Generic;
using System.Linq;

namespace Rextester
{
    public class Program
    {
        class Korv
        {
            public string Name;
            public List<int> Items;
        }
        public static void Main(string[] args)
        {
            List<Korv> list1 = new List<Korv>
            {
                new Korv() { Name = "abc", Items = new List<int>{ 2, 6, 9 } },
                new Korv() { Name = "def", Items = new List<int>{ 1, 5, 8 } },
                new Korv() { Name = "ghf", Items = new List<int>{ 1, 5, 8 } },
            };
            List<Korv> list2 = new List<Korv>
            {
                new Korv() { Name = "abc", Items = new List<int>{ 4, 11, 14 } },
                new Korv() { Name = "def", Items = new List<int>{ 5, 12, 15 } },
                new Korv() { Name = "xyz", Items = new List<int>{ 16, 17, 18 } } 
            };
            HashSet<string> joinedNames = new HashSet<string>();
            var joined = list1.Join(list2, x => x.Name, x => x.Name, (a, b) => { 
                joinedNames.Add(a.Name); 
                return new Korv() { Name = a.Name, Items = a.Items.Concat(b.Items).ToList() }; 
            });
            var everything = joined.Union(list1.Where(x => joinedNames.Contains(x.Name) == false)).Union(list2.Where(x => joinedNames.Contains(x.Name) == false));
            Console.WriteLine(string.Join(Environment.NewLine, everything.Select(x => x.Name + " - " + string.Join(",", x.Items.Select(y => y.ToString())))));
        }
    }
}

Show compiler warnings [ + ] Show input
Compilation time: 0,17 sec, absolute running time: 0,13 sec, cpu time: 0,14 sec, average memory usage: 14 Mb, average nr of threads: 3