nilavpatel/todo.cqrs

CQRS and Event Sourcing sample application and architecture

CQRS + ES + DDD + .NET 5.0

CQRS stands for Command and Query Responsibility Segregation
ES stands for Event Sourcing
DDD stands for Domain Driven Design

Features

• Commands and handlers
• Domain models (Aggregates)
• Aggregate repository
• Event sourcing using EventStore
• Domain events and handlers (Projections)
• Integration events and handlers (Cross module projections)
• Read models
• Query controllers
• Unit of work, Read repository, Write repository
• Auto registration of commands, events and their handlers
• Unit of work for multiple aggregates
• Snapshots, Snapshot repository, Snapshot storage in eventstore db
• Checkpoint, Checkpoint repository, Checkpoint storage in eventstore db
• Class for sequential GUIDs
• Entity tracking for write repository and no tracking for read repository

Notes:

• Inherit domain model with AggregateRoot or SnapshotAggregateRoot<Snapshot>.
• Domain model must have a parameterless constructor with a private access modifier.
• Set all setters with private modifier to all properties in the domain model.
• Domain layer has no dependencies except Contracts layer.
• All business logic and validation should be written in domain models.
• Contracts contain Command and Event classes, no business logic should be written in Contracts.
• All database updates are done from EventHandler only.
• Use IReadRepository for query controllers.
• Use sequential Guids CombGuid.NewGuid() instead of Guid.NewGuid().
• Use IUnitOfWork to update data in event handlers.
• Start background processor before starting web app
• AggregateVersion start from 1, where in EventStore event version start from 0.

How to configure Eventstore?

Diagrams: