using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    class Entry

    {

        public Entry(string year, double service, double earnings)

        {

            this.Year = year;

            this.Service = service;

            this.Earnings = earnings;

        }

        public override string ToString()

        {

            return String.Format("{0} {1} {2}", this.Year, this.Service, this.Earnings);

        }

        public string Year;

        public double Service;

        public double Earnings;

    }

    public static void Main()

    {

        var list = new List<Entry>(){

            new Entry("20002001", 1 , 100.00),

            new Entry("20012002", .5  , 100.00),

            new Entry("20022003", 1.0 , 100.00),

            new Entry("20042005", 1.0 , 50.00),

            new Entry("20052006", 1.0 , 50.00)};

        var result = list.GroupAdjacentBy((x, y) => x.Service == 1 && y.Service == 1).

            Select(g => new Entry(

                g.First().Year.Substring(0,4) + g.Last().Year.Substring(4,4),

                g.Sum(e => e.Service),

                g.Sum(e => e.Earnings)));

​

        Console.WriteLine(result.ElementAt(2));

    }

}

​

public static class LinqExtensions

{

    public static IEnumerable<IEnumerable<T>> GroupAdjacentBy<T>(

        this IEnumerable<T> source, Func<T, T, bool> predicate)

    {

        using (var e = source.GetEnumerator())

        {

            if (e.MoveNext())

            {

                var list = new List<T> { e.Current };

                var pred = e.Current;

                while (e.MoveNext())

                {

                    if (predicate(pred, e.Current))

                    {

                        list.Add(e.Current);

                    }

                    else

                    {

                        yield return list;

                        list = new List<T> { e.Current };

                    }

                    pred = e.Current;

                }

                yield return list;

            }

        }

    }

}