static void Main(string[] args)
        {
            Employee emp = new Employee("Ivan","Ivanov","IT",2000);
            EmployeeRepository empRep = new EmployeeRepository();
            empRep.employees.Add(emp);

            Message msg = new Message(new AvgSalary(2, 2000), empRep);

            BinaryWorker bw = new BinaryWorker();
            byte[] bytes = bw.messageToBytes(msg);

            Message fromBytes = bw.bytesToMessage(bytes);
        }
 public void Add(Employee emp)
 {
     if (emp == null) return;
     employees.Add(emp);
 }