public static IEnumerable <EmployeeDTO> ListEmployeesDTOs()
        {
            var listEmployee = LoadEmployees();
            var listDTO      = from emp in listEmployee
                               select ContractFactory.BuildContract(emp).GenerateDTO();

            return(listDTO);
        }
        public static IEnumerable <EmployeeDTO> SearchEmployeesDTOs(List <ParamEmployeeId> paramEmployeeIds)
        {
            var listEmployee = LoadEmployees();
            var listDTO      = from emp in listEmployee
                               where EmployeeUtils.BelongsToIds(emp, paramEmployeeIds)
                               select ContractFactory.BuildContract(emp).GenerateDTO();

            return(listDTO);
        }
        public static EmployeeDTO GetEmployeeDTOById(int id)
        {
            var listEmployee = LoadEmployees();
            var listDTO      = from emp in listEmployee
                               where emp.Id == id
                               select ContractFactory.BuildContract(emp).GenerateDTO();

            if (listDTO.Any())
            {
                var dto = listDTO.First();
                return(dto);
            }
            else
            {
                return(null);
            }
        }