using System;

using System.Linq;

using System.Collections.Generic;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        List<string> mylist = new List<string>(new string[] { "x8.11", "x8.22", "x8.2" });

        mylist = mylist.OrderByAlphaNumeric(x=>x).ToList();

        mylist.ForEach(Console.WriteLine);

    }

​

}

​

    public static class IEnumerableSortingExtensions

    {

        /// Code from http://stackoverflow.com/a/11720793

​

​

        public static IEnumerable<T> OrderByAlphaNumeric<T>(this IEnumerable<T> source, Func<T, string> selector)

        {

            int max = source

                .SelectMany(i => Regex.Matches(selector(i), @"\d+").Cast<Match>().Select(m => (int?)m.Value.Length))

                .Max() ?? 0;

​

            return source.OrderBy(i => Regex.Replace(selector(i), @"\d+", m => m.Value.PadLeft(max, '0')));

        }

    }