public Employee(string employeeNo, Period period, string firstName, string lastName)
{
if (period == null)
{
throw new ArgumentNullException("period");
}
period.CheckCreatingEmployee();
if (string.IsNullOrWhiteSpace(employeeNo))
{
throw new EmployeeArgumentException("Employee", "employeeNo");
}
id = new EmployeeId(employeeNo, period.Id);
this.firstName = firstName;
if (string.IsNullOrWhiteSpace(lastName))
{
throw new EmployeeArgumentException("Employee", "lastName");
}
this.lastName = lastName;
employeePointState = EmployeePointState.UnCalculated;
}