using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main(string[] args)

    {

        List<int> email = new List<int>() { 60, 50, 70, 30, 80, 65, 90, 75, 55 };

​

        Console.WriteLine("<Results>");

        foreach (var batch in email.Batch(3))

        {

            Console.WriteLine("<Result>");

            Console.WriteLine(String.Join("\n", batch.Select(x => "  <Mark>"+x+"</Mark>")));

            Console.WriteLine("  <Total>" + batch.Sum() + "</Total>");

            Console.WriteLine("</Result>");

        }

        Console.WriteLine("</Results>");

    }

}

​

public static class Extensions

{

    public static IEnumerable<IEnumerable<T>> Batch<T>(this IEnumerable<T> items,

                                                  int maxItems)

    {

        return items.Select((item, inx) => new { item, inx })

                    .GroupBy(x => x.inx / maxItems)

                    .Select(g => g.Select(x => x.item));

    }

}