using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

           List<int> numbers = new List<int> { 1, 2, 3, 4, 5, 6, 7, 8 };

​

            var result = numbers.Select((v, i) => new { Value = v, Index = i / 3 })

                                .GroupBy(x => x.Index)

                                .Select(x => x.Select(z => z.Value).ToList());

​

​

​

            foreach (var item in result)

            {

                foreach (var item2 in item)

                {

                    Console.WriteLine(item2);

                }

                Console.WriteLine("------------------");

            }           

    }

}