using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        List<Items> items = new List<Items>(){

            new Items(1, 10, 20, 30, 40, 50),

            new Items(2, 10, 19, 30, 40, 50),

            new Items(3, 9, 20, 40, 30, 50),

            new Items(4, 10, 20, 31, 40, 12),

            new Items(5, 9, 20, 30, 40, 50),

            new Items(6, 9, 20, 41, 40, 12)

        };

        // Group your values

        var groupedItems = items.GroupBy(i => new { i.ItemA, i.ItemB })

                                .ToList();

        for(var g = 0; g < groupedItems.Count(); g++)

        {

            Console.Write("List[{0}]: ",g);

            foreach(var innerGroup in groupedItems.ElementAt(g))

            {

                Console.Write("{{{0}}},",String.Join(",",innerGroup.ToArray()));    

            }

            Console.WriteLine();

        }

    }

    public class Items

    {

        public string Id { get; set;}

        public string ItemA { get; set;}

        public string ItemB { get; set;}

        public string ItemC { get; set;}

        public string ItemD { get; set;}

        public string ItemE { get; set;}

        public Items(int id, int a, int b, int c, int d, int e)

        {

            Id = id.ToString();

            ItemA = a.ToString();

            ItemB = b.ToString();

            ItemC = c.ToString();

            ItemD = d.ToString();

            ItemE = e.ToString();

        }

        public string[] ToArray()

        {

            return new string[]{ Id, ItemA, ItemB, ItemC, ItemD, ItemE };   

        }

    }

}

​

​