using System;
using System.Collections.Generic;
using System.Linq;

public class Example1{
  
  public static void Main(){

    // A collection of all possible combination of female-male pairs

    IEnumerable<Person> males = Person.SomePersons
       .Where(p => p.Sex == Sex.Male);

    IEnumerable<Person> females = Person.SomePersons
       .Where(p => p.Sex == Sex.Female);

    var pairs = males     // SelectMany flattens the nested sequences
      .SelectMany(m => females
                    .Select(f => new{First=f, Second=m}));

    foreach(var pair in pairs)
          Console.WriteLine("{0} <-> {1}", pair.First, pair.Second);
  }
}