using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    static void Main()

    {

        var strings = new []

        {

            "AB1001_A",

            "AB1001_B",

            "AB1002_2",

            "AB1002_C",

            "AB1003_0",

            "AB1003_",

            "AB1003_B",

            "AB1003_A",

            "AB1001_0",

            "AB1001_1",

            "AB1001_2",

            "AB1001_C",

            "AB1002_B",

            "AB1002_A",

        };

​

        static int compare(string x, string y)

        {

            var xParts = x.Split('_', StringSplitOptions.RemoveEmptyEntries);

            var yParts = y.Split('_', StringSplitOptions.RemoveEmptyEntries);

​

            if (xParts.Length != yParts.Length)

                return yParts.Length - xParts.Length;

​

            if (xParts.Length == 0)

                return 0;

​

            int comp = string.Compare(xParts[0], yParts[0], StringComparison.Ordinal);

​

            if (comp != 0 || xParts.Length == 1)

                return comp;

​

            if (char.IsDigit(xParts[1][0]) && !char.IsDigit(yParts[1][0]))

                return -1; // Digits go before non-digit.

​

            if (!char.IsDigit(xParts[1][0]) && char.IsDigit(yParts[1][0]))

                return 1; // Digits go before non-digit.

​

            return string.Compare(yParts[1], xParts[1], StringComparison.Ordinal);

        }

​

        var stringList = strings.ToList();

        stringList.Sort(compare);

​

        Console.WriteLine("Sorted list:");

        Console.WriteLine(string.Join("\n", stringList));

​

        var stringArray = strings.ToArray();

        Array.Sort(stringArray, compare);

​

        Console.WriteLine("\nSorted array:");

        Console.WriteLine(string.Join("\n", stringArray));

​

        var sequence = strings.Select(element => element);

        var sortedSeq = sequence.OrderBy(element => element, Comparer<string>.Create(compare));

​

        Console.WriteLine("\nSorted sequence:");

        Console.WriteLine(string.Join("\n", sortedSeq));

    }

}