dotnet-ddd

.NET Core DDD + Hexagonal/Clean Architecture

This skill guides building .NET Core applications following Domain-Driven Design with Hexagonal (Ports & Adapters) and Clean Architecture principles.

When NOT to Use This Skill

• Simple CRUD operations without complex business rules
• Basic EF Core or Dapper query optimization (use sqlserver-expert)
• Generic C# coding tasks unrelated to domain architecture
• Frontend or API design without domain modeling aspects

Skill Interactions

• For SQL query optimization inside QueryHandlers, defer to sqlserver-expert skill
• This skill defines the QueryHandler structure; sqlserver-expert optimizes the SQL within

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Architecture Overview

Dependency Flow (Inward)

Presentation (APIs / Workers)
       │
       ▼
   Application (UseCases, Queries, DTOs)
       │
       ▼
     Domain (Entities, Value Objects, Domain Events, Interfaces)
       │
       ▲
 Infrastructure (Repos, External Services, Adapters)
       │
       ▼
     Core (Shared kernel, Base abstractions)

The dependency rule: Dependencies always point inward. Domain has ZERO dependencies on Infrastructure or Application. Infrastructure implements Domain interfaces (Ports & Adapters).

Modular Solution Structure

Each bounded context is a module with three projects:

src/Modules/{ModuleName}/
├── {Namespace}.Application/       # Use Cases, Queries, DTOs, Handlers
│   ├── UseCases/                  # Command-side (write operations)
│   │   └── {Name}UseCase.cs
│   ├── UseCaseHandlers/           # UseCase implementations
│   │   └── {Name}UseCaseHandler.cs
│   ├── Queries/                   # Query-side (read operations)
│   │   └── Get{Name}Query.cs
│   ├── QueryHandlers/             # Query implementations (Dapper)
│   │   └── Get{Name}QueryHandler.cs
│   ├── DTOs/                      # Data Transfer Objects
│   ├── Interfaces/                # Application-level service interfaces
│   └── Helpers/                   # Application utilities
│
├── {Namespace}.Domain/            # Pure domain model
│   ├── Entities/                  # Aggregates and Entities
│   ├── ValueObjects/              # Value Objects
│   ├── Enums/                     # Domain enumerations
│   ├── Events/                    # Domain Events
│   ├── Interfaces/                # Repository interfaces (Ports)
│   └── Exceptions/                # Domain-specific exceptions
│
└── {Namespace}.Infrastructure/    # Adapters
    ├── Repositories/              # Repository implementations (EF Core)
    ├── Services/                  # External service adapters
    └── Persistence/               # DB configurations, migrations