servicesAddHttpClient

The `services.AddHttpClient` method is a built-in extension in .NET Core and .NET 5+ used to configure and register HTTP client services within an application's dependency injection (DI) container. Introduced as part of the Microsoft.Extensions.Http package, it simplifies the process of creating and managing HTTP clients, particularly for scenarios like calling RESTful APIs or external services.

This method allows developers to define named HTTP client instances with customizable configurations, such as base addresses, handlers, and policies. By registering clients through DI, they become reusable across the application, adhering to the principle of dependency injection for better testability and maintainability. The syntax typically follows `services.AddHttpClient<TClient>(clientBuilder => { ... })`, where `TClient` is a custom client class or an interface, and `clientBuilder` enables configuration before registration.

Key features include support for typed clients, which enforce interface-based contracts, and the ability to add custom handlers (e.g., for logging, retries, or authentication) via the `AddHttpMessageHandler` method. Additionally, `services.AddHttpClient` integrates with the `IHttpClientFactory`, a factory pattern implementation that dynamically creates and manages HTTP clients based on predefined configurations.

This approach is particularly useful in microservices architectures, where multiple HTTP clients may interact with different services. It reduces boilerplate code by abstracting low-level HTTP client creation and lifecycle management, while also enabling centralized configuration and error handling. The method is widely used alongside other .NET HTTP client utilities, such as `HttpClient` and `IHttpClientFactory`, to build scalable and maintainable web applications.