/// <see cref="IPortableObject"/>
 void IPortableObject.WriteExternal(IPofWriter writer)
 {
     writer.WriteString(FIRST_NAME, m_firstName);
     writer.WriteString(LAST_NAME, m_lastName);
     writer.WriteObject(HOME_ADDRESS, m_addrHome);
     writer.WriteObject(WORK_ADDRESS, m_addrWork);
     writer.WriteDictionary(PHONE_NUMBERS, m_dictPhoneNumber,
                            typeof(string), typeof(PhoneNumber));
     writer.WriteDate(BIRTH_DATE, m_dtBirth);
 }