How to Properly Inject Typed HttpClient Alongside Other Parameters in ASP.NET Core

Learn how to efficiently inject a `Typed HttpClient` along with other parameters into your services in ASP.NET Core, and understand the differences between typed and named HttpClients.
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Understanding the Challenge of Injecting Typed HttpClient in a Class with Additional Parameters

In modern ASP.NET Core applications, dependency injection is a powerful feature that simplifies the management of class dependencies. However, there are instances where you may encounter challenges when trying to inject a Typed HttpClient along with other parameters. This issue often confuses developers, especially those who are still familiarizing themselves with the intricacies of the IServiceProvider and HttpClient usage.

In this guide, we will dissect a scenario where a service class needs to utilize a HttpClient along with other non-service parameters, focusing on an efficient solution to achieve the desired functionality.

The Problem

Suppose you have a service class defined as follows:

[[See Video to Reveal this Text or Code Snippet]]

What Goes Wrong

When you attempt to configure your services with:

[[See Video to Reveal this Text or Code Snippet]]

You may encounter a problem: the HttpClient instance being injected is not the same one configured with the specified BaseAddress. Instead, you receive an instance with empty properties. The reason is that GetRequiredService<HttpClient>() retrieves a generic HttpClient, not the one with the configured settings.

A Solution Overview

There is a clearer way to approach this by utilizing an overload for the AddHttpClient method that allows you to inject HttpClient while constructing your service class.

The Solution: Use Overload of AddHttpClient

Instead of injecting HttpClient and other parameters separately, we can handle the instantiation within the AddHttpClient method. The updated configuration would look like the following:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Solution

Service Registration: By using AddHttpClient<IMyService, MyService>, the HttpClient configuration is encapsulated within the same registration block. This ties the lifecycle of the HttpClient to the service's configuration directly, ensuring that you get the correctly configured instance.

Lambda Expression: A lambda expression takes care of setting the BaseAddress and then returns a new instance of MyService.

Dependency Injection: The ILogger<MyService> and the HttpClient, where the former is still fetched using GetRequiredService, are injected seamlessly, allowing you to avoid manual misconfiguration.

Benefits of this Approach

Single Responsibility: All related configurations are encapsulated in one spot, enhancing maintainability.

Correct Configuration: You receive a fully configured HttpClient every time, which assures you have your desired settings.

Conclusion

Injecting a Typed HttpClient while passing additional parameters can initially seem complex, but by understanding how to properly use dependency injection in ASP.NET Core, you can simplify the process. This method ensures that your HttpClient is not only injected but also precisely configured according to the specified requirements.

Now that you have this solution, you can confidently manage service dependencies in your applications without encountering the pitfalls of incorrectly configured services. Happy coding!