using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var imageUrls = new List<string>() { "DSC_1.jpg", "DSC_10.jpg", "DSC_2.jpg" };

​

        var comparer = new NumericCompare();

        imageUrls.Sort(comparer);

        Console.WriteLine(String.Join("\n",imageUrls));

    }

    public class NumericCompare : IComparer<string>

    {

       public int Compare(string x, string y)

       {

            int input1,input2;

            input1=int.Parse(x.Substring(x.IndexOf('_')+1).Split('.')[0]); 

            input2= int.Parse(y.Substring(y.IndexOf('_')+1).Split('.')[0]);

            return Comparer<int>.Default.Compare(input1,input2);

       }

   }

}