using System;

using System.Collections.Generic;

using System.Linq;

​

namespace ConsoleApplication1

{

    public class Program

    {

        public static void Main()

        {

            var rnd = new Random();

            var collection = Enumerable

                .Range(1, 100)

                .Select(_ => new Item(rnd.Next(30)))

                .ToList();

​

            var filteredCollection = collection.MaxByRange(x => x.Prop);

​

            foreach (var item in filteredCollection)

            {

                Console.WriteLine(item.Prop);

            }

​

        }

    }

​

    public class Item

    {

        public int Prop { get; set; }

        public Item(int prop)

        {

            Prop = prop;

        }

    }

​

    public static class EnumerableExtensions

    {

        public static List<T> MaxByRange<T, TR>(this IEnumerable<T> source, Func<T, TR> selector) where TR : IComparable<TR>

        {

            var max = default(TR);

            var result = new List<T>();

​

            foreach (var item in source)

            {

                if (selector(item).CompareTo(max) > 0)

                {

                    max = selector(item);

​

                    result.Clear();

                    result.Add(item);

                }

​

                else if (selector(item).CompareTo(max) == 0)

                {

                    result.Add(item);

                }

            }

​

            return result;

        } 

    }

}

​