private void UpdateMeetings(List <Meeting> xx)
 {
     this.Meetings.Clear();
     foreach (var item in xx)
     {
         var meeting = new MeetingItemVM(item);
         this.Meetings.Add(meeting);
     }
 }
        private void NewMeeting()
        {
            var meeting = new CoreObjects.Meeting();

            meeting.TreeId  = this.TreeNodeSelected.Id;
            meeting.Subject = this.TreeNodeSelected.Name;
            var meetingvm = new MeetingItemVM(meeting);

            this.Meetings.Add(meetingvm);
            EditMeeting edit = new EditMeeting(meeting);

            edit.Show();
        }