UsecatR 0.0.2

UsecatR

UsecatR is a lightweight Use Case (Interactor) execution pipeline for .NET, designed to fit naturally into Clean Architecture applications.

It provides a simple and explicit way to execute Use Cases, with support for pipeline behaviors such as logging, validation, transactions, caching, and more — without heavy frameworks or magic conventions.

Think of UsecatR as a clean, minimal alternative to MediatR, focused exclusively on the Application Layer.

Installation

UsecatR is distributed as a single NuGet package.

dotnet add package UsecatR

Core Concepts

Basic Usage

1. Define a Use Case request

using UsecatR.Abstractions;

public sealed record CreateCustomer(
    string Name,
    string Email
) : IUseCaseRequest<Guid>;

2. Implement the Use Case handler

using UsecatR.Abstractions;

public sealed class CreateCustomerHandler
    : IUseCaseHandler<CreateCustomer, Guid>
{
    public Task<Guid> HandleAsync(CreateCustomer request, CancellationToken ct)
    {
        // Application logic goes here
        return Task.FromResult(Guid.NewGuid());
    }
}

3. Register UsecatR and handlers

using UsecatR.DependencyInjection;

builder.Services.AddUsecatR(
    typeof(CreateCustomerHandler).Assembly
);

4. Execute the Use Case

using UsecatR.Abstractions;

public sealed class CustomersController : ControllerBase
{
    private readonly IUsecatR _UsecatR;

    public CustomersController(IUsecatR UsecatR)
    {
        _UsecatR = UsecatR;
    }

    [HttpPost]
    public async Task<IActionResult> Create(CreateCustomer input, CancellationToken ct)
    {
        var id = await _UsecatR.ExecuteAsync<CreateCustomer, Guid>(input, ct);
        return Ok(id);
    }
}

Pipeline Behaviors

Pipeline behaviors allow you to add cross-cutting concerns around Use Case execution.

Behavior contract

public interface IUseCaseBehavior<in TRequest, TResult>
    where TRequest : IUseCaseRequest<TResult>
{
    Task<TResult> HandleAsync(
        TRequest request,
        UseCaseHandlerDelegate<TResult> next,
        CancellationToken ct);
}

Example: Logging behavior

using UsecatR.Abstractions;

public sealed class LoggingBehavior<TRequest, TResult>
    : IUseCaseBehavior<TRequest, TResult>
    where TRequest : IUseCaseRequest<TResult>
{
    public async Task<TResult> HandleAsync(
        TRequest request,
        UseCaseHandlerDelegate<TResult> next,
        CancellationToken ct)
    {
        Console.WriteLine($"Starting {typeof(TRequest).Name}");
        var result = await next();
        Console.WriteLine($"Finished {typeof(TRequest).Name}");
        return result;
    }
}

Clean Architecture Alignment

UsecatR is designed to live in the Application Layer.

License

MIT