public IHttpActionResult Put(int key, Employee employee)
        {
            if (key != employee.ID)
            {
                return BadRequest("The ID of customer is not matched with the key");
            }

            Employee originalEmployee = _employees.FirstOrDefault(c => c.ID == key);
            _employees.Remove(originalEmployee);
            _employees.Add(employee);
            return Ok(employee);
        }
        public IHttpActionResult Post(Employee employee)
        {
            employee.ID = _employees.Count + 1;
            _employees.Add(employee);

            return Created(employee);
        }