How to sort a string array by numeric style?

Question

I have a filenames array, I want to sort it by numeric style, please give to me a solution.

Example1:

Original array: [name99.txt, name98.txt, name100.txt]
Sorted array: [name98.txt, name99.txt, name100.txt]
(Using string sorting, result of sorting is [name100.txt, name98.txt, name99.txt])

Example2:

Original array: [a99.txt, b98.txt, b100.txt]
Sorted array: [a99.txt, b98.txt, b100.txt]
(Using string sorting, result of sorting is [a99.txt, b100.txt, b99.txt])

Answer 1

string[] ar = new string[] { "name99.txt", "name98.txt", "name100.txt" };
Array.Sort(ar, (a, b) => int.Parse(Regex.Replace(a, "[^0-9]", "")) - int.Parse(Regex.Replace(b, "[^0-9]", "")));

foreach (var a in ar)
    Console.WriteLine(a);

The above assumed that your files are allways called name###.txt. For the real numeric sorting use the following more complicated version:

public static void NumericalSort(string[] ar)
{
    Regex rgx = new Regex("([^0-9]*)([0-9]+)");
    Array.Sort(ar, (a, b) =>
    {
        var ma = rgx.Matches(a);
        var mb = rgx.Matches(b);
        for (int i = 0; i < ma.Count; ++i)
        {
            int ret = ma[i].Groups[1].Value.CompareTo(mb[i].Groups[1].Value);
            if (ret != 0)
                return ret;

            ret = int.Parse(ma[i].Groups[2].Value) - int.Parse(mb[i].Groups[2].Value);
            if (ret != 0)
                return ret;
        }

        return 0;
    });
}

static void Main(string[] args)
{
    string[] ar = new string[] { "a99.txt", "b98.txt", "b100.txt" };

    NumericalSort(ar);

    foreach (var a in ar)
        Console.WriteLine(a);
}