using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var table1 = Enumerable.Range(1, 10);

        var table2 = Enumerable.Range(1, 10).Where(n => (n & 1) == 0).OfType<int?>();

        var table3 = Enumerable.Range(1, 10).OfType<int?>();

        var query = from t1 in table1

                    join t2 in table2 on t1 equals t2 into j

                    from t2 in j.DefaultIfEmpty()

                    join t3 in table3 on t2 equals t3 into j2

                    from t3 in j2.DefaultIfEmpty()

                    select (t1, t2, t3);

        query.ToList().Dump();

    }

}