Tips and Tricks #23: Implement Domain Events for Loose Coupling

Use domain events to decouple components and enable reactive architectures.

Code Snippet

// Domain Event
public record OrderPlacedEvent(
    string OrderId,
    string UserId,
    decimal TotalAmount,
    DateTime PlacedAt
);

// Event Publisher
public interface IEventPublisher
{
    Task PublishAsync(T @event) where T : class;
}

// In Order aggregate
public class Order
{
    private readonly List

Why This Helps

• Decouples bounded contexts
• Enables eventual consistency patterns
• Supports audit trails and event sourcing

How to Test

• Verify events are raised correctly
• Test handlers in isolation

When to Use

Microservices, complex domains, when actions trigger side effects in other modules.

Performance/Security Notes

Consider idempotency for event handlers. Use outbox pattern for reliable publishing.

References

• https://docs.microsoft.com/en-us/dotnet/architecture/microservices/microservice-ddd-cqrs-patterns/domain-events-design-implementation

Try this tip in your next project and share your results in the comments!