Thắc mắc giữa Rich Class và POCO Class

[trantran02 (AnonymousLearner)]

Mọi người cho em hỏi là class sau đây là Rich class hay POCO class ạ? Em có đọc qua tài liệu của 2 định nghĩa này thì theo em hiểu nó là Rich class do bản thân nó có chứa behaviors và business logic, ví dụ như method AddOrderItem. Nhưng trong cuốn ebook NET-Microservices-Architecture-for-Containerized-NET-Applications lại ghi là “It is important to note that this is a domain entity implemented as a POCO class. It does not have any direct dependency on Entity Framework Core or any other infrastructure framework. This implementation is as it should be in DDD, just C# code implementing a domain model.”
Có vẻ như em hiểu vấn đề chưa đúng lắm. Mn giúp em với, em cảm ơn nhiều.
Code:

using Microsoft.eShopOnContainers.Services.Ordering.Domain.Seedwork;
using Ordering.Domain.Events;
using Ordering.Domain.Exceptions;
using System;
using System.Collections.Generic;
using System.Linq;

namespace Microsoft.eShopOnContainers.Services.Ordering.Domain.AggregatesModel.OrderAggregate
{
    public class Order
        : Entity, IAggregateRoot
    {
        // DDD Patterns comment
        // Using private fields, allowed since EF Core 1.1, is a much better encapsulation
        // aligned with DDD Aggregates and Domain Entities (Instead of properties and property collections)
        private DateTime _orderDate;

        // Address is a Value Object pattern example persisted as EF Core 2.0 owned entity
        public Address Address { get; private set; }

        public int? GetBuyerId => _buyerId;
        private int? _buyerId;

        public OrderStatus OrderStatus { get; private set; }
        private int _orderStatusId;

        private string _description;



        // Draft orders have this set to true. Currently we don't check anywhere the draft status of an Order, but we could do it if needed
        private bool _isDraft;

        // DDD Patterns comment
        // Using a private collection field, better for DDD Aggregate's encapsulation
        // so OrderItems cannot be added from "outside the AggregateRoot" directly to the collection,
        // but only through the method OrderAggrergateRoot.AddOrderItem() which includes behaviour.
        private readonly List<OrderItem> _orderItems;
        public IReadOnlyCollection<OrderItem> OrderItems => _orderItems;

        private int? _paymentMethodId;

        public static Order NewDraft()
        {
            var order = new Order();
            order._isDraft = true;
            return order;
        }

        protected Order()
        {
            _orderItems = new List<OrderItem>();
            _isDraft = false;
        }

        public Order(string userId, string userName, Address address, int cardTypeId, string cardNumber, string cardSecurityNumber,
                string cardHolderName, DateTime cardExpiration, int? buyerId = null, int? paymentMethodId = null) : this()
        {
            _buyerId = buyerId;
            _paymentMethodId = paymentMethodId;
            _orderStatusId = OrderStatus.Submitted.Id;
            _orderDate = DateTime.UtcNow;
            Address = address;

            // Add the OrderStarterDomainEvent to the domain events collection 
            // to be raised/dispatched when comitting changes into the Database [ After DbContext.SaveChanges() ]
            AddOrderStartedDomainEvent(userId, userName, cardTypeId, cardNumber,
                                       cardSecurityNumber, cardHolderName, cardExpiration);
        }

        // DDD Patterns comment
        // This Order AggregateRoot's method "AddOrderitem()" should be the only way to add Items to the Order,
        // so any behavior (discounts, etc.) and validations are controlled by the AggregateRoot 
        // in order to maintain consistency between the whole Aggregate. 
        public void AddOrderItem(int productId, string productName, decimal unitPrice, decimal discount, string pictureUrl, int units = 1)
        {
            var existingOrderForProduct = _orderItems.Where(o => o.ProductId == productId)
                .SingleOrDefault();

            if (existingOrderForProduct != null)
            {
                //if previous line exist modify it with higher discount  and units..

                if (discount > existingOrderForProduct.GetCurrentDiscount())
                {
                    existingOrderForProduct.SetNewDiscount(discount);
                }

                existingOrderForProduct.AddUnits(units);
            }
            else
            {
                //add validated new order item

                var orderItem = new OrderItem(productId, productName, unitPrice, discount, pictureUrl, units);
                _orderItems.Add(orderItem);
            }
        }

        public void SetPaymentId(int id)
        {
            _paymentMethodId = id;
        }

        public void SetBuyerId(int id)
        {
            _buyerId = id;
        }

        public void SetAwaitingValidationStatus()
        {
            if (_orderStatusId == OrderStatus.Submitted.Id)
            {
                AddDomainEvent(new OrderStatusChangedToAwaitingValidationDomainEvent(Id, _orderItems));
                _orderStatusId = OrderStatus.AwaitingValidation.Id;
            }
        }

        public void SetStockConfirmedStatus()
        {
            if (_orderStatusId == OrderStatus.AwaitingValidation.Id)
            {
                AddDomainEvent(new OrderStatusChangedToStockConfirmedDomainEvent(Id));

                _orderStatusId = OrderStatus.StockConfirmed.Id;
                _description = "All the items were confirmed with available stock.";
            }
        }

        public void SetPaidStatus()
        {
            if (_orderStatusId == OrderStatus.StockConfirmed.Id)
            {
                AddDomainEvent(new OrderStatusChangedToPaidDomainEvent(Id, OrderItems));

                _orderStatusId = OrderStatus.Paid.Id;
                _description = "The payment was performed at a simulated \"American Bank checking bank account ending on XX35071\"";
            }
        }

        public void SetShippedStatus()
        {
            if (_orderStatusId != OrderStatus.Paid.Id)
            {
                StatusChangeException(OrderStatus.Shipped);
            }

            _orderStatusId = OrderStatus.Shipped.Id;
            _description = "The order was shipped.";
            AddDomainEvent(new OrderShippedDomainEvent(this));
        }

        public void SetCancelledStatus()
        {
            if (_orderStatusId == OrderStatus.Paid.Id ||
                _orderStatusId == OrderStatus.Shipped.Id)
            {
                StatusChangeException(OrderStatus.Cancelled);
            }

            _orderStatusId = OrderStatus.Cancelled.Id;
            _description = $"The order was cancelled.";
            AddDomainEvent(new OrderCancelledDomainEvent(this));
        }

        public void SetCancelledStatusWhenStockIsRejected(IEnumerable<int> orderStockRejectedItems)
        {
            if (_orderStatusId == OrderStatus.AwaitingValidation.Id)
            {
                _orderStatusId = OrderStatus.Cancelled.Id;

                var itemsStockRejectedProductNames = OrderItems
                    .Where(c => orderStockRejectedItems.Contains(c.ProductId))
                    .Select(c => c.GetOrderItemProductName());

                var itemsStockRejectedDescription = string.Join(", ", itemsStockRejectedProductNames);
                _description = $"The product items don't have stock: ({itemsStockRejectedDescription}).";
            }
        }

        private void AddOrderStartedDomainEvent(string userId, string userName, int cardTypeId, string cardNumber,
                string cardSecurityNumber, string cardHolderName, DateTime cardExpiration)
        {
            var orderStartedDomainEvent = new OrderStartedDomainEvent(this, userId, userName, cardTypeId,
                                                                      cardNumber, cardSecurityNumber,
                                                                      cardHolderName, cardExpiration);

            this.AddDomainEvent(orderStartedDomainEvent);
        }

        private void StatusChangeException(OrderStatus orderStatusToChange)
        {
            throw new OrderingDomainException($"Is not possible to change the order status from {OrderStatus.Name} to {orderStatusToChange.Name}.");
        }

        public decimal GetTotal()
        {
            return _orderItems.Sum(o => o.GetUnits() * o.GetUnitPrice());
        }
    }
}