EventSourcing

EventSourcing is a .NET library that implements basis for event sourcing pattern.

Documentation is currently W.I.P.

Installation

Install the package via .NET CLI:

dotnet add package Sl4vP0weR.EventSourcing

Usage

Defining Event Sources

Define type that can be a source for events.

public record User(string Name, string Surname, string PhoneNumber) : IEventSource

Defining Events

Define event representing state changes:

public record UserCreatedEvent(DateTime CreatedAt, User User) : IEvent;

Defining Event Handlers

Define event handler as a type to listen events:

// suitable for any type of event.
public class AuditEventHandler : IEventHandler<IEvent>
{
    public int Order => int.MaxValue; // should run after other handlers
    
    public void Handle(IEvent @event) => PerformAudit(@event);
    
    private void PerformAudit(IEvent @event) 
    {
         // save to the file/database, or send as a message to the message broker/web api, or whatever suits your needs.
        ...
    }
}

Handling events

Create a method event handler instance:

IEventHandler<IEvent> handler = DelegateEventHandler<IEvent>.From(PerformAudit);

or class event handler instance:

IEventHandler<IEvent> handler = new AuditEventHandler();

and listen to the incoming global events:

handler.Listen();

or to the specific source

IEventSource user = new User("Frederic", "Chopin", "123456789");

handler.Listen(user);

Raising events

Create an event:

User user = new User("Frederic", "Chopin", "123456789");

var @event = new UserCreatedEvent(DateTime.UtcNow, user);

Raise event:

@event.Raise();

or with specific sources (still raising global):

@event.Raise(user);

or asynchronous approach:

await @event.RaiseAsync(user);

License

This project is licensed under the MIT License.
See the LICENSE file for details.