private Validation <Error, CreateEntityCommand> ValidateCreateEntityMsg(CreateEntityCommand msg)
 => from x in ValidateNonNull(msg)
 from y in (
 public Try <Validation <Error, EntityDto> > Execute(CreateEntityCommand msg)
 => ()
 => from x in ValidateCreateEntityMsg(msg)
 let y                 = x.ToEntity()
                 let z = _entityRepository.Create(y)
                         select z.ToEntityDto();