using System;

using System.Linq;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        string baIds = "1,x,2";

        List<long ? > result = null;

        if (!string.IsNullOrEmpty(baIds))

        {

            long temp;

            result = baIds.Split(',').Select(e => long.TryParse(e, out temp) ? temp : (long ? )null).ToList();

        }

​

        foreach (long ? item in result)

        {

            Console.WriteLine(item.HasValue ? item.ToString() : "null");

        }

    }

}