using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var arr = new []

            {

                "a1a",

                "5ac",

                "1",

                "12",

                "2",

                "11",

                "5aa",

                "3",

                "5ab",

                "1aa",

                "a2b",

                "abb11ca",

                "1b",

                "aba11ca"

            };

​

            var ordered = arr.Select(str => {

                        string[] parts = SplitIntoPrefixNumberSuffix(str);

                        int number = int.Parse(parts[1]);

                        return new { str, parts, number };

                    })

                    .OrderBy(x => x.number).ThenBy(x => x.parts[2]).ThenBy(x => x.parts[0])

                    .Select(x => x.str);

​

            Console.WriteLine("sorted array: ");

            foreach (var s in ordered)

            {

                Console.WriteLine("{0}", s);

            }

        }

​

​

        public static string[] SplitIntoPrefixNumberSuffix(string str)

        {

            char[] numChar = new char[] { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };

            var numLoc = str.IndexOfAny(numChar);

            var nums = "";

            foreach (var c in str)

            {

                if (Char.IsDigit(c))

                    nums = nums + c;

            }

            var prefix = str.Substring(0, numLoc);

            var suffix = str.Substring(numLoc + nums.Count());

            return new string[] { prefix, nums, suffix };

        }

    }

​