Dependency injection: HttpClient or HttpClientFactory?
Summary
HttpClient
can only be injected inside Typed clients- for other usages, you need
IHttpClientFactory
- In both scenarios, the lifetime of
HttpClientMessageHandler
is managed by the framework, so you are not worried about (incorrectly) disposing theHttpClients
.
Examples
In order to directly inject HttpClient
, you need to register a specific Typed service that will receive the client:
services.AddHttpClient<GithubClient>(c => c.BaseAddress = new System.Uri("https://api.github.com"));
Now we can inject that inside the typed GithubClient
public class GithubClient
{
public GithubClient(HttpClient client)
{
// client.BaseAddress is "https://api.github.com"
}
}
You can't inject the HttpClient
inside AnotherClient
, because it is not typed to AnotherClient
public class AnotherClient
{
public AnotherClient(HttpClient client)
{
// InvalidOperationException, can't resolve HttpClient
}
}
You can, however:
1. Inject the IHttpClientFactory
and call CreateClient()
. This client will have BaseAddress
set to null
.
2. Or configure AnotherClient
as a different typed client with, for example, a different BaseAdress
.
Update
Based on your comment, you are registering a Named client. It is still resolved from the IHttpClientFactory.CreateClient() method, but you need to pass the 'name' of the client
Registration
services.AddHttpClient("githubClient", c => c.BaseAddress = new System.Uri("https://api.github.com"));
Usage
// note that we inject IHttpClientFactory
public HomeController(IHttpClientFactory factory)
{
this.defaultClient = factory.CreateClient(); // BaseAddress: null
this.namedClient = factory.CreateClient("githubClient"); // BaseAddress: "https://api.github.com"
}
Sadly I cannot comment, but only Post an answer. Therefore I suggest you should check out the following Links:
https://docs.microsoft.com/en-us/dotnet/architecture/microservices/implement-resilient-applications/use-httpclientfactory-to-implement-resilient-http-requests
https://aspnetmonsters.com/2016/08/2016-08-27-httpclientwrong/
Regarding your Questions it more or Less boils down to this:
Q1 -> IHttpClientFactory handles the connection pools of HttpClient instances and this will help you regarding load and dispose problems as discribed in the links, if the HttpClient is used wrong.
Q2 -> yes you should use factory.create client according to microsoft docs