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Vali-Mediator

Vali-Mediator is a lightweight .NET library that implements the Mediator pattern with full CQRS support. It provides a clean separation between request senders and request handlers, a powerful pipeline for cross-cutting concerns, and a rich ecosystem of extension packages.

Why Vali-Mediator?​

  • Zero external dependencies in the core package (only Microsoft.Extensions.DependencyInjection.Abstractions)
  • Targets .NET 7, 8, and 9 — multi-target from one package
  • Result pattern built-in — no exceptions for business logic failures
  • Extensible pipeline — add behaviors, pre/post processors without touching business code
  • Complete ecosystem — resilience, caching, observability, and idempotency as optional packages

Dispatch Flow​

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Package Ecosystem​

PackageNuGetDescription
Vali-MediatorNuGetCore: mediator, pipeline, result pattern
Vali-Mediator.AspNetCoreNuGetMaps Result<T> to HTTP responses
Vali-Mediator.ResilienceNuGetRetry, Circuit Breaker, Timeout, Bulkhead, Hedge, Rate Limiter, Chaos, Fallback
Vali-Mediator.CachingNuGetDeclarative pipeline caching
Vali-Mediator.ObservabilityNuGetOpenTelemetry tracing, metrics, observers
Vali-Mediator.IdempotencyNuGetIdempotent request deduplication

Key Features​

Requests & CQRS​

  • IRequest<TResponse> + IRequestHandler<TRequest, TResponse>
  • Void shorthand: IRequest → IRequest<Unit>
  • SendOrDefault — returns default when no handler registered
  • SendAll — parallel execution via Task.WhenAll

Notifications​

  • Fan-out to N handlers via INotification
  • Priority-ordered execution
  • PublishStrategy: Sequential, Parallel, or ResilientParallel
  • INotificationFilter<T> — conditionally skip handlers

Pipeline​

  • IPipelineBehavior<TRequest, TResponse> for requests
  • IPipelineBehavior<TDispatch> for notifications/fire-and-forget
  • Auto-discovered pre/post processors
  • Declarative timeout via IHasTimeout
  • Dead letter queue for failed notifications

Result Pattern​

  • Result<T> and Result (void) — readonly structs
  • ErrorType enum maps to HTTP status codes
  • Functional operations: Map, Bind, Tap, Match, OnFailure

Streaming​

  • IStreamRequest<T> + CreateStream() → IAsyncEnumerable<T>

Version​

Current stable version: 2.0.0