using System;
using System.Collections.Generic;
using System.Linq;
public class Program
{
public static void Main()
var xs = new int?[] { 1, null, 2 };
var ys = new int?[] { 1, null, 2 };
foreach (var x in xs.Join(ys, x => x, y => y, (x, y) => x))
Console.WriteLine("Yield x = " + x);
}