A simple NH mapping that is not working. Seems to be a cascade/delete issue.

Attendee.cs

namespace CRIneta.Web.Core.Domain
{
public class Attendee
{
    protected readonly string email;
    protected readonly Meeting meeting;
    protected readonly int attendeeId;

    protected Attendee()
    {
        // no args constructor used for NHibernate. So much for persistence ignorance!
    }

    public Attendee(string email, Meeting meeting)
    {
        this.email = email;
        this.meeting = meeting;
    }

    public virtual string Email
    {
        get { return email; }
    }

    public virtual Meeting Meeting
    {
        get { return meeting; }
    }

    public override bool Equals(object obj)
    {
        var other = obj as Attendee;
        if(other == default(Attendee))
            return false;

        return (email == other.email);
    }
}
}

Mappings.xml

<class name="Meeting" table="Meetings">
    <id name="MeetingId" column="Id" type="Int32" unsaved-value="0">
        <generator class="native" />
    </id>
    <property name="Title" column="Title" length="255" not-null="true" />
    <property name="StartTime" column="StartsAt" type="DateTime" not-null="true" />
    <property name="EndTime" column="EndsAt" type="DateTime" not-null="true" />
    <property name="Description" column="Description" type="StringClob" not-null="true" />
    <property name="Presenter" column="Presenter" length="255" not-null="true" />

    <many-to-one name="Facility" column="FacilityId" not-null="true" lazy="false" class="Facility" foreign-key="FK_Meetings_Facilities" />

  <bag name="Attendees" access="nosetter.camelcase" cascade="all-delete-orphan" lazy="false" inverse="true">
    <key column="MeetingId" />
    <one-to-many class="Attendee" />
  </bag>

</class>

<class name="Attendee" table="Attendees">
  <id name="attendeeId" column="Id" type="Int32" unsaved-value="0" access="field">
    <generator class="native" />
  </id>
  <many-to-one name="Meeting" column="MeetingId" class="Meeting" not-null="true" access="nosetter.camelcase" />
  <property name="email" column="Email" length="100" not-null="true" access="field" />
</class>

Meeting.cs

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

namespace CRIneta.Web.Core.Domain
{
public class Meeting
{
    private readonly IList<Attendee> attendees;

    public Meeting()
    {
        attendees = new List<Attendee>();
    }

    public virtual int AttendeeCount
    {
        get { return attendees.Count(); }
    }

    protected virtual IEnumerable<Attendee> Attendees
    {
        get { return attendees; }
    }

    public virtual int MeetingId { get; set; }
    public virtual string Title { get; set; }
    public virtual DateTime StartTime { get; set; }
    public virtual DateTime EndTime { get; set; }
    public virtual string Description { get; set; }
    public virtual string Presenter { get; set; }
    public virtual Facility Facility { get; set; }

    public virtual void AddAttendee(Attendee attendee)
    {
        if (!AlreadyAttending(attendee))
            attendees.Add(attendee);
    }

    /// <summary>
    /// Returns whether the attendee is already attending.
    /// </summary>
    /// <param name="attendee">The attendee.</param>
    /// <returns></returns>
    private bool AlreadyAttending(Attendee attendee)
    {
        return attendees.Contains(attendee);
    }
}
}