using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var fhList = new List<FileHierarchy>() {

                new FileHierarchy(1,null,true),

            new FileHierarchy(2,1,null),

            new FileHierarchy(3,1,null),

            new FileHierarchy(4,2,null),

            new FileHierarchy(5,null,false),

            new FileHierarchy(6,5,null),

            new FileHierarchy(7,6,null),

            new FileHierarchy(8,null,true),

            new FileHierarchy(9,8,null)

        };

        var result = fhList.Where(fh => fh.NeedsShowing.HasValue && 

                      fh.NeedsShowing == false

                      && fh.ParentID.HasValue == false).ToList();

        foreach(var r in result) {

            Console.WriteLine(r.ID); 

        }

    }

}

​

public class FileHierarchy

{

    public FileHierarchy(int id, int? pid, bool? ns) {

        ID = id;

        ParentID = pid;

        NeedsShowing = ns;

    }

  public int ID { get; set; }

  public int? ParentID { get; set; }

  public bool? NeedsShowing { get; set; }

}