A little test of using a binary search algorithm to find indexes of values in a sorted list. Also just a little comparison between binary and linear/sequential searching.

BinarySearch.cs

using System;
using System.Collections.Generic;

namespace BinarySearch
{
    class Program
    {
        static void Main(string[] args)
        {
            List<int> list = new List<int>() { 5, 8, 900, 1, 22, 52, 567, 666, 123, 256, 765, 0, 500 }; // example list
            int search = 666; // the value to find the index of
            list.Sort(); // sorts list
            int low = 0, high = list.Count, mid = 0, prevmid = 0, counter = 0; // declare low, high, middle, previousmiddle, and counter variables
            while (search != list[mid]) // binary searching algorithm
            {
                mid = (low + high) / 2; // middle point (average)
                if (mid == prevmid) { Console.WriteLine("Impossible to find."); Console.Read(); return; } // if prevmid and mid are equal (meaning the calculation was exact same as last time), we don't want to stay in this infinite loop that we can't get a result from, so break/return
                prevmid = mid; // assign mid to prevmid
                if (list[mid] > search) high = mid; // cut out everything from mid and above
                else low = mid; // cut out everything from mid and below
                counter++; // increment number of steps taken
            }
            // output results
            Console.WriteLine("list = {" + String.Join(",", list.ConvertAll<string>(i => { return i.ToString(); })) + "}");
            Console.WriteLine("list[" + mid + "] = " + list[mid]);
            Console.WriteLine("Using a binary search algorithm, " + counter + " steps are taken to solve this calculation.");
            Console.WriteLine("Using a linear/sequential search algorithm, " + mid + " steps are taken to solve this calculation.");
            Console.Read();
        }
    }
}

How long does it take to sort the list?

I don't know how Microsoft does it, but I'd assume maybe something like this: http://pastie.org/6006391