using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var tickets = new List<Tix>();

        var ordered = new List<Tix>();

        ordered.AddRange(tickets.Where(t=>string.IsNullOrEmpty(t.LevelUp)));

        Console.WriteLine("Hello World");

    }

}

​

public class Tix {

    public string Component {get;set;}

    public string Parent { get; set;}

    public string LevelUp { get; set; }

    public Tix(string c,string p,string lu){

        Component=c;

        Parent=p;

        LevelUp=lu;

    }

}