Passing IHttpClientFactory to .NET Standard class library

Question

There's a really cool IHttpClientFactory feature in the new ASP.NET Core 2.1 https://www.hanselman.com/blog/HttpClientFactoryForTypedHttpClientInstancesInASPNETCore21.aspx

I'm trying to use this feature in my ASP.NET Core 2.1 Preview-2 app but I need to use the HttpClient in my class libraries which are in .NET Standard 2.0

Once I perform AddHttpClient in ConfigureServices() in Startup.cs, how do I pass this HttpClientFactory or a specific named HttpClient to an API client I created in my .NET Standard 2.0 class library? This client pretty much handles all the API calls I make to a third party.

Basically, I'm just trying to get the specific named HttpClient into my thirdPartyApiClient.

Here's my code in ConfigureServices():

public void ConfigureServices(IServiceCollection services)
{
    // Create HttpClient's
    services.AddHttpClient("Api123Client", client =>
    {
         client.BaseAddress = new Uri("https://api123.com/");
         client.DefaultRequestHeaders.Add("Accept", "application/json");
    });
    services.AddHttpClient("Api4567Client", client =>
    {
         client.BaseAddress = new Uri("https://api4567.com/");
         client.DefaultRequestHeaders.Add("Accept", "application/json");
    });
}

Gal

Answer 1

First, your library class' constructor should take an HttpClient param, so you can inject an HttpClient into it. Then, the easiest method (mentioned in the link article as well for what it's worth) is to simply add a specific HttpClient for that library class:

services.AddHttpClient<MyLibraryClass>(...);

Then, of course, register your library class for injection, if you haven't already:

services.AddScoped<MyLibraryClass>();

Then, when your library class is instantiated to be injected into something, it too will be injected with the HttpClient you specified for it.

Alternatively, you can manually specify an HttpClient instance to inject via:

services.AddScoped(p => {
    var httpClientFactory = p.GetRequiredService<IHttpClientFactory>();
    return new MyLibraryClass(httpClientFactory.Create("Foo"));
});

Eriha

Update: AddHttpClient already handles the registration of the service for you in this scenario. You may get an error if you do it in the above approach. Refer: github.com/dotnet/extensions/issues/1079 – Pappano

Answer 2

Nowadays there is a NuGet package Microsoft.Extensions.Http offering the IHttpClientFactory to .NET Standard 2.0

Gardiner

Exactly what I needed. – Duff

This also works for .NET Standard 2.1. Thanks @Gardiner – Overscore

Lifesaver! The docs were saying it was part of Microsoft.Extensions.DependencyInjection which I already had installed. – Swat