Description

When registering multiple HttpClient services using HttpClientFactoryServiceCollectionExtensions.AddHttpClient with the same interface, the resulting services share the same configuration (e.g., BaseAddress). This behavior leads to unexpected results when injecting these services as an IEnumerable into a controller or service.

Reproduction Steps

1. Define an interface and two typed clients that implement it:

   public interface ITypedClient { }

   public class TypedClientA : ITypedClient
   {
       private readonly HttpClient _httpClient;

       public TypedClientA(HttpClient httpClient)
       {
           _httpClient = httpClient;
       }
   }

   public class TypedClientB : ITypedClient
   {
       private readonly HttpClient _httpClient;

       public TypedClientB(HttpClient httpClient)
       {
           _httpClient = httpClient;
       }
   }

2. Register the services in Program.cs:

builder.Services.AddHttpClient<ITypedClient, TypedClientA>(httpClient =>
{
    httpClient.BaseAddress = new Uri("https://exampleA.com");
});

builder.Services.AddHttpClient<ITypedClient, TypedClientB>(httpClient =>
{
    httpClient.BaseAddress = new Uri("https://exampleB.com");
});

3. Inject the services and observe their BaseAddress:

public class SomeController : Controller
{
    private readonly IEnumerable<ITypedClient> _typedClients;

    public SomeController(IEnumerable<ITypedClient> typedClients)
    {
        _typedClients = typedClients;
    }
}

Expected behavior

When multiple HttpClient instances are registered using the same interface with AddHttpClient, each implementation should retain its unique configuration. Specifically:

• TypedClientA should be configured with a BaseAddress of https://exampleA.com.
• TypedClientB should be configured with a BaseAddress of https://exampleB.com.

When these services are injected as IEnumerable<ITypedClient> into a controller or service, the collection should contain both implementations, each retaining its respective configuration. For example:

1. TypedClientA should make HTTP requests to https://exampleA.com.
2. TypedClientB should make HTTP requests to https://exampleB.com.

The system should correctly distinguish between the two implementations without overwriting or merging their configurations.

Actual behavior

When multiple HttpClient instances are registered using the same interface with AddHttpClient, the configurations for the services are overwritten. Specifically:

• Both TypedClientA and TypedClientB end up sharing the same BaseAddress, which is determined by the last registered configuration.

For example:

• If TypedClientB is registered after TypedClientA, both clients will have the BaseAddress set to https://exampleB.com.
• If the order of registration is reversed, both clients will have the BaseAddress set to https://exampleA.com.

When these services are injected as IEnumerable<ITypedClient> into a controller or service, both implementations refer to the same HttpClient configuration, resulting in unexpected and incorrect behavior.

Regression?

This issue has been present since at least .NET 7 and continues to occur in .NET 8 and .NET 9. The behavior where multiple HttpClient instances with the same interface overwrite each other's configurations has persisted across these versions.

Testing with previous versions of .NET (7, 8, and 9) confirms that this issue has been ongoing, suggesting it may be a long-standing bug or unintended behavior in the framework's AddHttpClient method.

Known Workarounds

No response

Configuration

No response

Other information

No response