Domain-Driven Design in Modern .NET Applications

Domain-Driven Design (DDD) has become an essential approach for building complex .NET applications. In this article, I’ll explore how DDD principles can be effectively implemented in modern .NET 8 applications, particularly in cloud-native environments.

Understanding the Core of Domain-Driven Design

Domain-Driven Design is more than just a technical architecture—it’s a methodology for tackling complexity in the heart of software. The approach emphasizes:

  1. A focus on the core domain and domain logic
  2. Basing complex designs on a model of the domain
  3. Collaborating with domain experts to improve the application model
  4. Learning through continuous iteration

Strategic Design vs. Tactical Design

DDD comprises both strategic and tactical aspects:

Strategic Design helps us understand the big picture:

  • Bounded Contexts
  • Ubiquitous Language
  • Context Mapping

Tactical Design provides specific implementation patterns:

  • Entities
  • Value Objects
  • Aggregates
  • Domain Events
  • Repositories

Implementing DDD in .NET 8

.NET 8 offers several features that align well with DDD principles:

Rich Domain Models with Records and Pattern Matching

// Value Object using records
public record Money(decimal Amount, string Currency)
{
    public static Money Zero(string currency) => new(0, currency);
    
    public Money Add(Money other)
    {
        if (Currency != other.Currency)
            throw new InvalidOperationException("Cannot add different currencies");
            
        return this with { Amount = Amount + other.Amount };
    }
}

Immutability and Domain Events

public class Order
{
    private readonly List<OrderItem> _items = new();
    private readonly List<IDomainEvent> _events = new();
    
    public IReadOnlyCollection<OrderItem> Items => _items.AsReadOnly();
    public IReadOnlyCollection<IDomainEvent> Events => _events.AsReadOnly();
    
    public void AddItem(Product product, int quantity)
    {
        // Domain logic here
        _items.Add(new OrderItem(product.Id, product.Price, quantity));
        _events.Add(new OrderItemAddedEvent(Id, product.Id, quantity));
    }
}

Benefits in Cloud-Native Applications

When building cloud-native applications, DDD offers significant benefits:

  1. Clear boundaries for microservices - Bounded contexts provide natural service boundaries
  2. Resilience - Well-defined aggregates help manage consistency
  3. Scalability - Event-driven architecture enables loose coupling

Conclusion

Domain-Driven Design remains a powerful approach for managing complexity in modern .NET applications. By leveraging the latest features in .NET 8 and combining them with DDD principles, we can build more maintainable, flexible, and business-aligned systems.

In future articles, I’ll dive deeper into specific aspects of implementing DDD in cloud environments, particularly with Azure services.

What aspects of Domain-Driven Design would you like to learn more about? Let me know in the comments below!