Xpandables.Results.Pipelines 10.0.2

System.Results.Pipelines

Pipeline decorator implementations for cross-cutting concerns in the mediator pipeline.

📖 Overview

System.Results.Pipelines (NuGet: Xpandables.Results.Pipelines) provides concrete IPipelineDecorator<TRequest> implementations for validation, exception handling, pre/post-processing, unit-of-work, and event sourcing concerns. Namespace: System.Results.Pipelines.

Built for .NET 10 and C# 14.

✨ Pipeline Decorators

⚙️ Dependency Injection

C# 14 extension members on IServiceCollection:

services.AddXPipelineValidationDecorator();
services.AddXPipelineExceptionDecorator();
services.AddXPipelinePreHanderDecorator();
services.AddXPipelinePostHanderDecorator();
services.AddXPipelineRequireEntityUnitOfWorkDecorator();
services.AddXPipelineRequireDataUnitOfWorkDecorator();
services.AddXPipelineCommitDomainEventDecorator();
services.AddXPipelinePublishDomainEventDecorator();
services.AddXPipelineEnqueueIntegrationEventDecorator();

📦 Installation

dotnet add package Xpandables.Results.Pipelines

Project References: Xpandables.Results, Xpandables.Validation, Xpandables.Data, Xpandables.Entities, Xpandables.Events

🚀 Quick Start

Validation Decorator

Automatically validates requests before they reach the handler. If validation fails, a FailureResult is returned immediately.

// 1. Mark a request for validation
public sealed record CreateProductRequest(string Name, decimal Price) : IRequest<Guid>;

// 2. Implement a validator (from System.Validation)
public sealed class CreateProductValidator : ICompositeValidator<CreateProductRequest>
{
    public ValueTask<Result> ValidateAsync(
        CreateProductRequest request, CancellationToken ct)
    {
        if (string.IsNullOrWhiteSpace(request.Name))
            return ValueTask.FromResult<Result>(
                Result.Failure("Name", "Product name is required"));

        if (request.Price <= 0)
            return ValueTask.FromResult<Result>(
                Result.Failure("Price", "Price must be positive"));

        return ValueTask.FromResult(Result.Success().Build() as Result);
    }
}

// 3. Register the decorator
services.AddXPipelineValidationDecorator();
// The decorator intercepts CreateProductRequest, runs CreateProductValidator,
// and short-circuits with 400 if validation fails.

Exception Decorator

Catches unhandled exceptions and delegates to IRequestExceptionHandler<TRequest>.

// Implement a global exception handler for a specific request type
public sealed class CreateProductExceptionHandler
    : IRequestExceptionHandler<CreateProductRequest>
{
    public Task<Result> HandleAsync(
        RequestContext<CreateProductRequest> context,
        Exception exception,
        CancellationToken ct)
    {
        // Log, transform, or return a failure result
        return Task.FromResult<Result>(
            Result.InternalServerError(
                "CreateProduct", "Failed to create product", exception));
    }
}

services.AddXPipelineExceptionDecorator();

Pre/Post Handler Decorators

// Pre-handler: runs before the main handler
public sealed class AuditPreHandler : IRequestPreHandler<CreateProductRequest>
{
    public Task<Result> HandleAsync(
        RequestContext<CreateProductRequest> context, CancellationToken ct)
    {
        Console.WriteLine($"Creating product: {context.Request.Name}");
        return Task.FromResult(Result.Success().Build() as Result);
    }
}

// Post-handler: runs after the main handler succeeds
public sealed class NotifyPostHandler : IRequestPostHandler<CreateProductRequest>
{
    public Task<Result> HandleAsync(
        RequestContext<CreateProductRequest> context, CancellationToken ct)
    {
        Console.WriteLine($"Product created successfully.");
        return Task.FromResult(Result.Success().Build() as Result);
    }
}

services.AddXPipelinePreHanderDecorator();
services.AddXPipelinePostHanderDecorator();

Entity Framework Unit-of-Work Decorator

Wraps the handler in a transaction when the request implements IEntityRequiresUnitOfWork.

// Mark the request as requiring a transaction
public sealed record TransferFundsRequest(Guid FromId, Guid ToId, decimal Amount)
    : IRequest, IEntityRequiresUnitOfWork;

// The handler runs inside SaveChangesAsync — automatic commit on success, rollback on failure
public sealed class TransferFundsHandler(AppDbContext db)
    : IRequestHandler<TransferFundsRequest>
{
    public async Task<Result> HandleAsync(
        TransferFundsRequest request, CancellationToken ct)
    {
        var from = await db.Accounts.FindAsync([request.FromId], ct);
        var to = await db.Accounts.FindAsync([request.ToId], ct);

        from!.Balance -= request.Amount;
        to!.Balance += request.Amount;

        // No need to call SaveChangesAsync — the decorator handles it
        return Result.Success();
    }
}

services.AddXPipelineRequireEntityUnitOfWorkDecorator();

ADO.NET Unit-of-Work Decorator

Wraps the handler in an ADO.NET transaction when the request implements IDataRequiresUnitOfWork.

public sealed record BulkInsertOrdersRequest(List<OrderData> Orders)
    : IRequest, IDataRequiresUnitOfWork;

services.AddXPipelineRequireDataUnitOfWorkDecorator();

Event Sourcing Decorators

For event-sourced systems, these decorators manage domain event commits, publishing, and integration event outbox enqueuing.

// Register all event sourcing decorators at once
services.AddXPipelinePublishDomainEventDecorator();
services.AddXPipelineEnqueueIntegrationEventDecorator();
services.AddXPipelineCommitDomainEventDecorator();

// Or register the full event sourcing pipeline via System.Results.Tasks:
// services.AddXMediatorWithEventSourcingPipelines();

Custom Pipeline Decorator

// Implement IPipelineDecorator<TRequest> for custom cross-cutting concerns
public sealed class TimingDecorator<TRequest> : IPipelineDecorator<TRequest>
    where TRequest : class, IRequest
{
    public async Task<Result> HandleAsync(
        RequestContext<TRequest> context,
        RequestHandler nextHandler,
        CancellationToken ct)
    {
        var sw = Stopwatch.StartNew();
        Result result = await nextHandler(ct);
        sw.Stop();

        Console.WriteLine(
            $"{typeof(TRequest).Name} completed in {sw.ElapsedMilliseconds}ms");

        return result;
    }
}

// Register
services.AddXPipelineDecorator(typeof(TimingDecorator<>));

Complete Registration Example

// Standard pipeline with custom timing
services.AddXRequestHandlers(typeof(Program).Assembly);
services.AddXMediator();
services.AddXPipelineDecorator(typeof(TimingDecorator<>));  // custom
services.AddXPipelinePreHanderDecorator();
services.AddXPipelinePostHanderDecorator();
services.AddXPipelineRequireEntityUnitOfWorkDecorator();
services.AddXPipelineValidationDecorator();
services.AddXPipelineExceptionDecorator();

// ⚠️ Order matters! Decorators execute from outermost to innermost.
// ExceptionDecorator should be last registered (wraps everything).

📄 License

Apache License 2.0 — Copyright © Kamersoft 2025