Edition 0 Updated to asp. Net core 0
The custom Entity base class
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- Bu səhifədəki naviqasiya:
- Repository contracts (interfaces) in the domain model layer
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The custom Entity base class
The following code is an example of an Entity base class where you can place code that can be used the same way by any domain entity, such as the entity ID, equality operators , a domain event list per entity, etc. // COMPATIBLE WITH ENTITY FRAMEWORK CORE (1.1 and later) public abstract class Entity { int ? _requestedHashCode; int _Id; private List public virtual int Id { get { return _Id; } protected set { _Id = value; } } public List public void AddDomainEvent (INotification eventItem) { _domainEvents = _domainEvents ?? new List _domainEvents. Add (eventItem); } public void RemoveDomainEvent (INotification eventItem) { if (_domainEvents is null ) return ; _domainEvents. Remove (eventItem); } public bool IsTransient () { return this . Id == default (Int32); } public override bool Equals ( object obj) { if (obj == null || !(obj is Entity)) return false ; if (Object. ReferenceEquals ( this , obj)) return true ; if ( this . GetType () != obj. GetType ()) return false ; Entity item = (Entity)obj; if (item. IsTransient () || this . IsTransient ()) return false ; else return item. Id == this . Id ; } public override int GetHashCode () { if (! IsTransient ()) 212 CHAPTER 6 | Tackle Business Complexity in a Microservice with DDD and CQRS Patterns { if (!_requestedHashCode. HasValue ) _requestedHashCode = this . Id . GetHashCode () ^ 31 ; // XOR for random distribution. See: // https://learn.microsoft.com/archive/blogs/ericlippert/guidelines-and-rules- for-gethashcode return _requestedHashCode. Value ; } else return base . GetHashCode (); } public static bool operator ==(Entity left, Entity right) { if (Object. Equals (left, null )) return (Object. Equals (right, null )); else return left. Equals (right); } public static bool operator !=(Entity left, Entity right) { return !(left == right); } } The previous code using a domain event list per entity will be explained in the next sections when focusing on domain events. Repository contracts (interfaces) in the domain model layer Repository contracts are simply .NET interfaces that express the contract requirements of the repositories to be used for each aggregate. The repositories themselves, with EF Core code or any other infrastructure dependencies and code (Linq, SQL, etc.), must not be implemented within the domain model; the repositories should only implement the interfaces you define in the domain model. A pattern related to this practice (placing the repository interfaces in the domain model layer) is the Separated Interface pattern. As explained by Martin Fowler, “Use Separated Interface to define an interface in one package but implement it in another. This way a client that needs the dependency to the interface can be completely unaware of the implementation.” Following the Separated Interface pattern enables the application layer (in this case, the Web API project for the microservice) to have a dependency on the requirements defined in the domain model, but not a direct dependency to the infrastructure/persistence layer. In addition, you can use Dependency Injection to isolate the implementation, which is implemented in the infrastructure/ persistence layer using repositories. For example, the following example with the IOrderRepository interface defines what operations the OrderRepository class will need to implement at the infrastructure layer. In the current implementation of the application, the code just needs to add or update orders to the database, since queries are split following the simplified CQRS approach. // Defined at IOrderRepository.cs public interface IOrderRepository : IRepository { 213 CHAPTER 6 | Tackle Business Complexity in a Microservice with DDD and CQRS Patterns Order Add (Order order); void Update (Order order); Task GetAsync ( int orderId); } // Defined at IRepository.cs (Part of the Domain Seedwork) Yüklə 11,82 Mb. Dostları ilə paylaş:
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