CQRS & MediatR

Principle

RIVORA Framework separates read operations (Queries) from write operations (Commands) via MediatR.

Commands

Commands modify system state:

public record CreateOrderCommand(string CustomerId, List<OrderItemDto> Items)
    : IRequest<OrderDto>;

Queries

Queries read without modifying:

[Cached(Duration = 300)]
public record GetProductsQuery : IRequest<List<ProductDto>>;

Pipeline Behaviors

The MediatR pipeline executes in order:

1. LoggingBehavior: traces all requests
2. ValidationBehavior: automatic FluentValidation
3. AuthorizationBehavior: permission checks
4. CachingBehavior: caches queries (via [Cached] attribute)
5. TransactionBehavior: wraps commands in a transaction
6. PerformanceBehavior: logs slow requests (> 500ms)

Domain Events

Domain events are dispatched after SaveChanges:

public class OrderCreatedHandler : INotificationHandler<OrderCreatedEvent>
{
    public async Task Handle(OrderCreatedEvent evt, CancellationToken ct)
    {
        // Send email, webhook, notification...
    }
}