Application.Abstraction 1.0.0

Application.Abstraction

A lightweight .NET library that provides CQRS abstractions for application layers. Combine SimpleMediator with Core.Result to return explicit success and failure outcomes from commands and queries.

Features

• Command and query marker interfaces (ICommand, IQuery<T>)
• Base handlers with built-in Success() and Failure() builders
• Domain status enums (SuccessResult, FailureResult) for HTTP-friendly mapping
• JSON serialization support via JsonStringEnumConverter
• Zero boilerplate — handlers inherit fluent result building from CustomRequestHandler

Installation

dotnet add package Application.Abstraction

Or via Package Manager:

Install-Package Application.Abstraction

Quick Start

Define a command

using Application.Abstraction.CQRS.Command;

public sealed record CreateItemCommand(string Name) : ICommand<string>;

Implement a command handler

using Application.Abstraction.CQRS.Command;
using Application.Abstraction.CQRS.Result;
using Core.Result;

public sealed class CreateItemCommandHandler : CommandHandler<CreateItemCommand, string>
{
    public override Task<Result<string, SuccessResult, FailureResult>> Handle(
        CreateItemCommand request,
        CancellationToken cancellationToken)
    {
        return Task.FromResult<Result<string, SuccessResult, FailureResult>>(
            Success(SuccessResult.Created)
                .WithData(request.Name)
                .WithMessage("Item created")
                .Build());
    }
}

Define a query

using Application.Abstraction.CQRS.Query;

public sealed record GetItemQuery(string Id) : IQuery<ItemDto>;

Implement a query handler

using Application.Abstraction.CQRS.Query;
using Application.Abstraction.CQRS.Result;
using Core.Result;

public sealed class GetItemQueryHandler : QueryHandler<GetItemQuery, ItemDto>
{
    public override Task<Result<ItemDto, SuccessResult, FailureResult>> Handle(
        GetItemQuery request,
        CancellationToken cancellationToken)
    {
        var item = FindItem(request.Id);
        if (item is null)
        {
            return Task.FromResult<Result<ItemDto, SuccessResult, FailureResult>>(
                Failure(FailureResult.NotFound)
                    .WithMessage("Item not found")
                    .AppendErrors([$"No item with id '{request.Id}'"])
                    .Build());
        }

        return Task.FromResult<Result<ItemDto, SuccessResult, FailureResult>>(
            Success(SuccessResult.Done)
                .WithData(item)
                .Build());
    }
}

Commands without a response payload

Use ICommand (alias for ICommand<Unit>) when an operation succeeds without returning data:

public sealed record DeleteItemCommand(string Id) : ICommand;

public sealed class DeleteItemCommandHandler : CommandHandler<DeleteItemCommand>
{
    public override Task<Result<Unit, SuccessResult, FailureResult>> Handle(
        DeleteItemCommand request,
        CancellationToken cancellationToken)
    {
        return Task.FromResult<Result<Unit, SuccessResult, FailureResult>>(
            Success(SuccessResult.NoContent)
                .WithData(Unit.Value)
                .Build());
    }
}

Status Enums

SuccessResult

FailureResult

Map these statuses to HTTP responses, problem details, or integration events in your API layer — not inside domain handlers.

API Overview

All handlers return Result<TResponse, SuccessResult, FailureResult> from Core.Result.

Dependencies

• Core.Result — Result pattern with fluent builder API
• SimpleMediatorLib — Lightweight in-process mediator

Requirements

• .NET 10.0

License

MIT