using System;

using System.Linq;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        List<int> values = new() { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

        var chunked = values.Chunk(3);

        foreach (var chunk in chunked)

            Console.WriteLine("First value of chunk: " + chunk.First());

    }

}

​

static class Ex

{

    public static IEnumerable<IEnumerable<TValue>> Chunk<TValue>(

                    // change this from IEnumerable to List and watch it break

                    this IEnumerable<TValue> values,  

                    int chunkSize)

    {

        using(var enumerator = values.GetEnumerator())

        {

            while(enumerator.MoveNext())

            {

                yield return GetChunk(enumerator, chunkSize).ToList();

            }

        }

    }

​

    private static IEnumerable<T> GetChunk<T>(

                     IEnumerator<T> enumerator,

                     int chunkSize)

    {

        do

        {

            yield return enumerator.Current;

        } while(--chunkSize > 0 && enumerator.MoveNext());

    }

}