NPv.CQS.Abstractions 1.0.1

NPv.CQS.Abstractions

Minimal, dependency-free contracts for applications following the Command-Query Separation (CQS) pattern.

✨ Overview

NPv.CQS.Abstractions is a foundational library containing interfaces and contracts for building systems based on the Command‑Query Separation (CQS) principle.

It does not include any infrastructure or implementation — only the minimal building blocks that let infrastructure resolve and invoke handlers automatically.

Use this package in your domain, application, or core layers to define behaviors without pulling in any dependencies.

🔧 Interfaces Included

🟢 Commands

🔵 Queries

📦 Installation

dotnet add package NPv.CQS.Abstractions

💡 Examples

Define a command

public record CreateOrderCommandContext(Guid OrderId, decimal Amount) : ICommandContext;

public class CreateOrderCommand : ICommand<CreateOrderCommandContext>
{
    public Task ExecuteAsync(CreateOrderCommandContext context)
    {
        // Domain logic here
        return Task.CompletedTask;
    }
}

Define a query

public record FindById(Guid Id) : ICriterion;

public class FindOrderByIdQuery(IOrderService orders) : IQuery<FindById, Order>
{
    public Task<Order> AskAsync(FindById criterion) =>
        orders.GetAsync(criterion.Id);
}

Use in application code

public class OrdersController(ICommandExecutor exec, IQueryBuilder queries)
{
    public Task Create(Guid id, decimal amount) =>
        exec.ExecuteAsync(new CreateOrderCommandContext(id, amount));

    public Task<Order> Get(Guid id) =>
        queries.ForAsync<Order>().With(new FindById(id));
}

Note: ICommandExecutor is just a contract; infrastructure can provide an implementation that wraps execution in a Unit of Work (see NPv.Uow.Abstractions) or adds logging/telemetry/retries.

📚 Designed For Use With

• NPv.CQS.Infrastructure – runtime execution (dispatch via DI, Autofac/MS.DI modules)
• NPv.Uow.Abstractions – optional Unit of Work contract for transactional execution
• Any DI container or runtime

Author's Note

This library grew out of my long-standing personal interest in structuring and publishing open source packages. Over time, I’ve revisited and refined earlier internal utilities and ideas, giving them a more consistent shape and preparing them for wider reuse. Along the way, I’ve also taken the opportunity to explore how open source distribution and licensing work in the .NET ecosystem.

It’s a small step toward something I’ve always wanted to try — sharing practical, minimal tools that reflect years of learning, experimentation, and refinement.

Hopefully, someone finds it useful.

Nikolai 😛

⚖️ License

MIT — you are free to use this in commercial and open-source software.