using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var origArray = new[] {1,2,3,4,5,6};

        var segmentedArray1 = origArray

            .Select((item, index) => new { item, index })

            .GroupBy(x => x.index/3)

            .Select(@group => @group.Select(x=>x.item));

        var segmentedArray2 = Enumerable.Range(0, origArray.Count())

            .GroupBy(x => x/3)

            .Select(@group => @group.Select(index => origArray[index]));

        Console.WriteLine("Segmented Array 1");

        foreach(var array in segmentedArray1)

            Console.WriteLine("[{0}]", string.Join(", ", array));

        Console.WriteLine();

        Console.WriteLine("Segmented Array 2");

        foreach(var array in segmentedArray2)

            Console.WriteLine("[{0}]", string.Join(", ", array));

    }

}