using System;

using System.Collections.Generic;

​

class Program

{

    static void Main()

    {

        var list = new List<int>(){ 10, 5, 2, 100, 564, 879, 0 };

        //list.Sort();

        foreach (var item in list)

        {

            Console.WriteLine($"{item,3}: {list.BinarySearch(item),3}");

        }

        Console.WriteLine($"999: {list.BinarySearch(999),3}");

    }

}

​