public void DeleteByID(int ID)
{
StaffMember member = staff.Find(x => x.ID == ID);
if (member == null)
{
throw new ValidationException("No record found for id");
}
if ((member.GetType().Name == "Manager") && (((Manager)member).AssignedEmployees.Count != 0))
{
throw new IntegrityViolationException("There are employees assigned to this manager", ((Manager)member).AssignedEmployees);
}
staff.Remove(member);
}
