ConfigurePrimaryHttpMessageHandler<T>() not loading handler in ASP.NET Core 2.2

Describe the bug

Registering an HttpMessageHandler by generic type parameter is causing that handler to not be loaded.

To Reproduce

Steps to reproduce the behavior:

1. Using version ‘2.2’ of package ‘Microsoft.AspNetCore.App’, and ‘Microsoft.Extensions.Http’
2. Run this code at startup:

services.AddTransient<MyClientHttpMessageHandler>();
services
    .AddHttpClient<IMyClient, MyClient>()
    .ConfigurePrimaryHttpMessageHandler<MyClientHttpMessageHandler>();

1. Make an http client
2. Error is that MyClientHttpMessageHandler won’t be loaded or invoked.

Expected behavior

The handler is properly invoked when the client is used.

Workaround

services
    .AddHttpClient<IMyClient, MyClient>()
    .ConfigurePrimaryHttpMessageHandler(s => s.GetRequiredService<MyClientHttpMessageHandler>())

Additional context

This was the only issue I ran into upgrading a large project from netcoreapp2.1 to netcoreapp2.2.

.NET Core SDK (reflecting any global.json): Version: 2.2.101 Commit: 236713b0b7

Runtime Environment: OS Name: Windows OS Version: 10.0.14393 OS Platform: Windows RID: win10-x64 Base Path: C:\Program Files\dotnet\sdk\2.2.101\

Host (useful for support): Version: 2.2.0 Commit: 1249f08fed

[matt-lethargic]

Pardon my potential ignorance on this subject, but I thought the entire reason why we’ve got HttpClientFactory in .Net Core is help stop people newing up lots of HttpClient instances and using up resources. And I thought the issue really came from having many handlers and not the client itself.

If the work around for this is to use AddTransient then aren’t we creating this same problem and shouldn’t it be AddSingleton?

[sliekens]

Until the fix is published to NuGet, the code from https://github.com/aspnet/Extensions/issues/851#issuecomment-456119041 can be used as a workaround.

Example:

services.AddTransient<MyClientHttpMessageHandler>();
services
    .AddHttpClient<IMyClient, MyClient>()
    .ConfigurePrimaryHttpMessageHandler(sp => sp.GetRequiredService<MyClientHttpMessageHandler>());