using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;

namespace reactive_test
{
    class Program
    {
        public static void Main()
        {

            List<string> val1 = new List<string> {
    		  "File_1.txt","File_2.txt","File_1_Over.txt","File_2_Item.txt","File_1_Over.bat",
				"File_1_Over_test.bat","File_2_Standard.bat","File_2_Item_Standard.bat"
			};

            //val1.Sort(( x, y ) => string.Compare( Path.GetExtension(y), Path.GetExtension(x) ));
            var val = val1
                .GroupBy(f => Path.GetFileNameWithoutExtension(f))
                .OrderBy(group => group.Key);

            foreach (var group in val)
            {
                var q = group.OrderByDescending(f => Path.GetExtension(f));
                foreach (var f in q)
                {
                    Console.WriteLine(f);
                }
            }

        }
    }
}