public JsonResult Rename(string id, string value)
        {
            var command = new RenameParticipant
            {
                Id   = Guid.Parse(id),
                Name = value
            };

            Domain.Dispatcher.SendCommand(command);

            return(Json(command));
        }
        public IEnumerable Handle(Func <Guid, ParticipantAggregate> al, RenameParticipant command)
        {
            var agg = al(command.Id);

            if (agg.Name != command.Name)
            {
                yield return new ParticipantRenamed
                       {
                           Id   = command.Id,
                           Name = command.Name,
                       }
            }
            ;
        }