public CalendarEntryParticipantUninvited(TenantId tenantId, CalendarId calendarId, CalendarEntryId calendarEntryId, Participant participant)
        {
            this.TenantId = tenantId;
            this.CalendarId = calendarId;
            this.CalendarEntryId = calendarEntryId;
            this.Participant = participant;

            this.EventVersion = 1;
            this.OccurredOn = DateTime.Now;
        }
 public void Invite(Participant participant)
 {
     AssertionConcern.NotNull(participant, "The participant must be provided.");
     if(!this._invitees.Contains(participant)) {
         this.Apply(new CalendarEntryParticipantInvited(this._tenantId, this._calendarId, this._calendarEntryId,
             participant));
     }
 }