Develop Domain Layer with Tactical Domain-Driven Design Patterns in .NET 8 Microservices

4 min readMar 26, 2024

We are going to develop Ordering.Domain Layer with Tactical Domain-Driven Design Patterns.

I have just published course — .NET 8 Microservices: C# 12, DDD, CQRS, Vertical/Clean Architecture.

🎯 Tactical DDD: The Building Blocks

Tactical DDD serves as our guide in the intricate dance of software modeling, ensuring each component accurately reflects the business domain. Let’s break down these patterns:

Entities: The unique identities within our system, like individual orders, each carrying a unique OrderId, ensuring distinguishability even amongst similar attributes.
Value Objects: These are the characteristics or attributes, such as an Address in an order, crucial for completeness but devoid of a unique identity.
Aggregates: A cohesion of Entities and Value Objects, treated as a single unit, like an Order encapsulating OrderItems and PaymentDetails, safeguarding data consistency within its boundaries.
Aggregate Roots: The gatekeepers of Aggregates, like the Order entity in the Order Aggregate, serving as the primary point of interaction and ensuring the enforcement of business invariants.
Domain Events: Key business events that are significant to domain experts, for instance, an OrderCreated event.
Domain Services: Operations that encapsulate domain logic not naturally fitting within an entity or value object.

🛠️ Implementation in Ordering.Domain Layer

Our journey through the domain layer of the Ordering microservices is akin to an architect meticulously designing the blueprint of a complex structure. Here, we weave together Entities and Value Objects to form the narrative of our business logic. Aggregates and Aggregate Roots then bind these narratives into cohesive, self-contained stories, each with its integrity and rules.

🌟 Domain Modeling in Ordering Microservices with Tactical DDD

We’ll have exploration of domain modeling within the Ordering microservices. We’re applying the tactical patterns of Domain-Driven Design (DDD) to craft a domain model that truly reflects the intricate workings of our business logic.

📈 Application Use Cases: Ordering in Action

Our Ordering microservices revolve around core operations like managing Orders and integrating with the Basket service for order fulfillment. The tactical DDD patterns guide us in modeling these use cases, ensuring our architecture is aligned with business goals.

🎨 Creating the Domain Model

Let’s illustrate how these elements come together in our Ordering microservices:

Order Aggregate: At the heart of our service, orchestrating the order process and encapsulating Order Items.
Order Items: Each representing a product within an order.
Customer and Product Entities: Key players in our domain, integral to each order placed.

📌 Example in Action:

Consider an Order entity, our Aggregate Root, which orchestrates the behavior and rules around its associated OrderItems. It's not just a collection of items but a representation of a business transaction with rules around pricing, availability, and more.

public class Order : Entity // Aggregate Root
{
    private List<OrderItem> _orderItems;
    public IReadOnlyCollection<OrderItem> OrderItems => _orderItems.AsReadOnly();
    // Business logic and methods here
}

🔄 The Role of Tactical DDD in Clean Architecture

Incorporating these DDD concepts into our Ordering.Domain layer does more than just structure our code; it aligns our software design with the business domain, making it intuitive and adaptable. It allows our architecture to not just respond to current requirements but to evolve gracefully with the business, ensuring longevity and relevance.

📚 Diving into Ordering Microservices with DDD & Clean Architecture

Our journey navigates through the core essence and periphery of the Ordering system, revealing the blueprint of a system designed for resilience, flexibility, and domain-centricity.

🌟 Conclusion: Crafting Software that Reflects the Business

As we embrace Tactical Domain-Driven Design in our Ordering microservices, we’re not just coding; we’re crafting a model that mirrors the complexities and nuances of our business domain. Let’s continue to navigate this journey, shaping our microservices to be true reflections of the business domains they embody.