using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

          var theList = new List<string> { "4 tr", "plan 8", "", "12tr" };

            foreach (var item in theList

                    .OrderBy(x=> x.Length==0 )

                    .ThenBy(x => { return x.Length > 0 && x.Substring(0, 1).All(char.IsNumber); })

                    .ThenByDescending(x => int.Parse("0" +(new String(x.Where(Char.IsDigit).ToArray()))))

                    .ThenBy(x => x))

            {

                Console.WriteLine(item);

            };

    }

}