Aviant Library

A collection of .NET libraries for building clean, scalable applications using DDD, CQRS, and Event Sourcing.

Source-only: Aviant is currently consumed by adding it as a git submodule. NuGet packages are planned. See CleanDDDArchitecture for full usage examples.

Module Overview

src/
├── Kernel/          # Core abstractions, behaviours, pipeline
│   ├── Core/        # Entities, Value Objects, Specifications, Timing
│   ├── Application/ # MediatR pipeline behaviours, Commands, Queries
│   └── Infrastructure/ # Cross-cutting DI helpers
├── DDD/             # Domain-Driven Design building blocks
├── EventSourcing/   # Event-sourced aggregates and persistence
├── Identity/        # User identity and JWT authentication
├── Persistence/     # CQRS repositories and Unit of Work
├── Email/           # SMTP email service
└── Jobs/            # Hangfire background job runner

Quick Usage Examples

Add as a Git Submodule

git submodule add https://github.com/panosru/Aviant.git Library/Aviant
git submodule update --init --recursive

Register a Domain with the Kernel

// In your CrossCutting project
public static IServiceCollection AddMyDomain(this IServiceCollection services)
{
    services.AddDbContext<MyDbContext>(...);
    services.AddScoped<IMyRepository, MyRepository>();
    return services;
}

CQRS — Command + Handler

// Command
public sealed record CreateWeatherCommand(string City, double Temperature)
    : IRequest<WeatherDto>;

// Handler
public sealed class CreateWeatherCommandHandler
    : IRequestHandler<CreateWeatherCommand, WeatherDto>
{
    public async Task<WeatherDto> Handle(
        CreateWeatherCommand request,
        CancellationToken cancellationToken)
    {
        // ... domain logic
    }
}

Event Sourcing — Aggregate

public sealed class AccountAggregate : AggregateRoot<AccountAggregate, AccountId>
{
    public string Email { get; private set; } = string.Empty;

    public void Register(string email)
    {
        Apply(new AccountRegisteredEvent(Id, email));
    }

    protected override void When(IDomainEvent @event)
    {
        if (@event is AccountRegisteredEvent e)
            Email = e.Email;
    }
}

MediatR Pipeline Behaviours

Aviant registers these behaviours automatically (in order):

1. PerformanceBehaviour — logs slow requests (>500ms)
2. ValidationBehaviour — runs FluentValidation validators
3. UnhandledExceptionBehaviour — logs unhandled exceptions
4. RetryRequestProcessor — wraps handlers with Polly retry

Identity — JWT Authentication

// AccountService issues JWTs
services.AddAccountDomain();  // includes Identity + JWT issuance

// Other services validate JWTs
services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
    .AddJwtBearer(options => {
        options.TokenValidationParameters = new TokenValidationParameters
        {
            ValidateIssuerSigningKey = true,
            IssuerSigningKey = new SymmetricSecurityKey(key512),
            TokenDecryptionKey = new SymmetricSecurityKey(key256),
        };
    });

Module Dependency Graph

Kernel/Core
    └── Kernel/Application  (adds MediatR)
            └── Kernel/Infrastructure  (adds DI helpers)
DDD/Core
    └── DDD/Application      (extends Kernel/Application)
            └── DDD/Infrastructure
EventSourcing/Core
    └── EventSourcing/Application
            └── EventSourcing/Infrastructure
Identity/Core
    └── Identity/Application
            └── Identity/Infrastructure  (uses Kernel + DDD)
Persistence/Core
    └── Persistence/Application
            └── Persistence/Infrastructure
Email/Application
    └── Email/Infrastructure  (MailKit/MimeKit)
Jobs/Application
    └── Jobs/Infrastructure   (Hangfire)

Adding Aviant to a New Project

1. Add as a git submodule (see above)
2. Add Library/Aviant/Aviant.sln or individual .csproj references to your solution
3. Reference the modules you need from your domain projects
4. Register via the Add* extension methods in your Program.cs or DI registration class

Contribution

Pull requests and issue reports are welcome at github.com/panosru/Aviant.