PGS.DDD

Base libraries to start with CQRS and Event Sourcing

About

The solution consists of a number of projects, each published as a NuGet package on myget (https://www.myget.org/F/pgs-ddd/api/v2).

It should be ready to build out-of-the box. To work with the dependencies Paket is used. It is best handled from the command line. There is a handy VS plugin too.

PGS.DDD.Domain

This library should be referenced by the business domain. This is there Aggregate Roots, Entities and Domain Events live.

To create an event-sourced AR, just inherit the AggregateRoot<TId> class.

public class BusinessPerson : AggregateRoot<PersonId>
{ 
  private CompanyId _employer;

  public BusinessPerson(PersonId id) : base(id) { }

  public void StartWorkAt(CompanyId company)
  {
    // maybe some buisiness checks here to ensure consistent state?
  
    // push event
    Handle(StartedWorkingAt(company));
  }
  
  // each event is handled in a OnX method
  // it should be private or protected
  private void OnStartedWorkingAt(StartedWorkingAt ev)
  {
    _employer = ev.CompanyId;
  }
  
  // keeping event classes nested in their respective Aggregate Root
  // helps prevent name clashes
  public class StartedWorkingAt : DomainEvent
  {
    public StartedWorkingAt(CompanyId company)
    {
    }
  }
}

PGS.DDD.Application

This one should be referenced by Application services layer and contains base interfaces for their implementation:

• IEventPublisher, IEventHandler - for working with domain events
• IServiceBus - combines both above
• IIdConverter<TId> - to convert domain ids into event stream identifiers

PGS.DDD.Data.EventSourced

Implementation of an in-memory event store and a repository backed by events persisted to hard storage

PGS.DDD.Data.NEventStore

An implementation of event store using NEventStore.

PGS.DDD.ServiceBus

Basic, in-memory implementation of IServiceBus.