public void Invite(Participant participant)
 {
     AssertionConcern.AssertArgumentNotNull(participant, "The participant must be provided.");
     if (!this.invitees.Contains(participant))
     {
         Apply(new CalendarEntryParticipantInvited(this.tenant, this.calendarId, this.calendarEntryId, participant));
     }
 }
 public CalendarEntryParticipantUninvited(
     Tenant tenant,
     CalendarId calendarId,
     CalendarEntryId calendarEntryId,
     Participant participant)
 {
     this.Tenant = tenant;
     this.CalendarId = calendarId;
     this.CalendarEntryId = calendarEntryId;
     this.Participant = participant;
 }