using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        var a = new int[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

        Console.Write($"Batched list:\n\t");

        Console.WriteLine(a.Batch(3).Select(i => i.Join(",")).Join(";"));       

        Console.Write($"First from each batch:\n\t");

        Console.WriteLine(a.Batch(3).Select(i => i.First()).Join(","));

        Console.Write($"Second from each batch:\n\t");

        Console.WriteLine(a.Batch(3).Select(i => i.Skip(1).First()).Join(","));

        // This still fails!a

        // Console.WriteLine(a.Batch(3).ToList().Select(i => i.Join(",")).Join(";"));

        Console.Write($"Number of batches:\n\t");

        Console.WriteLine(a.Batch(3).Count());

        Console.Write($"Number of full batches:\n\t");

        Console.WriteLine(a.Batch(3).Where(i=>i.Count() == 3).Count());

    }

}

​

public static class BatchLinq

{

    public static IEnumerable<IEnumerable<T>> Batch<T>(this IEnumerable<T> source, int size)

    {

        if (size <= 0)

            throw new ArgumentOutOfRangeException("size", "Must be greater than zero.");

        using (var enumerator = source.GetEnumerator())

            while (enumerator.MoveNext())

            {

                var i = new BatchInner();

                var e = i.Batch(enumerator, size);

                yield return e;

                if (!i.done)

                    e.Count();

            }

    }

​

    private class BatchInner

    {

        public bool done = false;

        public IEnumerable<T> Batch<T>(IEnumerator<T> source, int size)

        {

            int i = 0;

            do yield return source.Current;

            while (++i < size && source.MoveNext());

            done = true;

        }

    }

​

    public static string Join<T>(this IEnumerable<T> s, string j)

    {

        return string.Join(j, s.ToArray());

    }

}