gistfile1.cs

class Program
    {
        static void Main(string[] args)
        {
            var store = new EmbeddableDocumentStore
            {
                DataDirectory = "Data"
            };

            store.Initialize();

            using (var session = store.OpenSession())
            {
                var event1 = new Event();
                var event2 = new Event();

                session.Store(event1);
                session.Store(event2);

                session.SaveChanges();

                var user1 = new User() { Fullname = "test2" };
                var user2 = new User() { Fullname = "test3" };

                session.Store(user1);
                session.Store(user2);

                session.SaveChanges();

                event1.Attendees = new List<Attendee>()
                                   {
                                       new Attendee() {UserId = user1.Id, Subscribed = DateTime.Now,},
                                       new Attendee() {UserId = user2.Id, Subscribed = DateTime.Now}
                                   };

                event2.Attendees = new List<Attendee>()
                                   {
                                       new Attendee() {UserId = user2.Id, Subscribed = DateTime.Now}
                                   };

                session.Store(event1);
                session.Store(event2);

                session.SaveChanges();


                var events = session.Query<Event>().ToList();
            }
           


        }
    }

    public class Event
    {
        public string Id { get;set;}
      public IEnumerable<Attendee> Attendees { get;set;}
    }

    public class Attendee
    {
	    public DateTime Subscribed { get;set;}
	    public string UserId { get;set;}
    }

    public class User
    {
	    public string Id { get;set;}
	    public string Fullname { get;set;}
    }