using System;

using System.Collections.Generic;

using System.Linq;

​

namespace ConsoleApplication1

{

    public class Program

    {

        public static void Main()

        {

            var getOnlyFirst = false;

​

            var collection = Enumerable

                .Range(1, 100)

                .Select(x => new Item(x));

​

            var condition = new Func<Item, bool>(x => x.Prop%15 == 0);

​

            var result = getOnlyFirst

                ? new List<Item> {collection.First(condition)}

                : collection

                    .Where(condition)

                    .ToList();

​

            foreach (var item in result)

            {

                Console.WriteLine(item.Prop);

            }

        }

    }

​

    class Item

    {

        public int Prop { get; set; }

        public Item(int prop)

        {

            Prop = prop;

        }

    }

}

​