using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        List<int> numbers = new List<int>();

        numbers.AddRange(new int?[]{1,"a"=="b"?2:null,3}.Where(x=>x!=null).Cast<int>());

        numbers.Dump();  // Dump() is an extension method provided by dotnetfiddle.net  }

}