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Extensions

Namespace: RA.Utilities.Feature.Extensions

The primary purpose of this namespace is to provide a fluent and discoverable API for registering your CQRS features (commands, queries, notifications, and their associated behaviors/validators) with the .NET dependency injection container.

It acts as the main entry point for wiring up the components of the RA.Utilities.Feature library — from the one-line AddMediator() bootstrap to the fluent AddFeature builders.

🔑 Key Purpose and Design​

The FeatureBuilderExtensions class uses the Builder Pattern to create a clean, readable, and chainable configuration experience. Let's break down how it works:

1. Bootstrapping the Feature:​

The process starts with an extension method on IServiceCollection, such as AddFeature or AddNotification.

// From: /RA.Utilities/Application/RA.Utilities.Feature/Extensions/FeatureBuilderExtensions.cs

public static FeatureBuilder<TRequest, TResponse> AddFeature<TRequest, TResponse, THandler>(
    this IServiceCollection services)
    where TRequest : IRequest<TResponse>
    where THandler : class, IRequestHandler<TRequest, TResponse>
{
    // Step 1: It registers the core handler for the request.
    services.AddScoped<IRequestHandler<TRequest, TResponse>, THandler>();

    // Step 2: It returns a new builder object.
    return new FeatureBuilder<TRequest, TResponse>(services);
}

2. Enabling Fluent Chaining:​

The key is that these methods return a FeatureBuilder or NotificationFeatureBuilder object. This builder object holds a reference to the IServiceCollection and provides its own methods for adding related components, like validators or pipeline behaviors.

3. Creating a Vertical Slice Configuration:​

This design allows you to define an entire vertical slice in a single, coherent block of code

example:

_ = services
      .AddFeature<CreateProductCommand, int, CreateProductHandler>() // 1. Starts with the extension method
      .AddDecoration<LoggingBehavior<CreateProductCommand, int>>()   // 2. Chains a behavior from the returned builder
      .AddValidator<CreateProductCommandValidator>();                       // 3. Chains a validator from the builder