Answer by Martin Dekker for Unable to resolve service for type 'System.Net.Http.HttpClient'

I had a similar error message trying to inject a wrapper for an external REST service to my controller as an interface. I needed to change the following in ConfigureServices:

services.AddHttpClient<IMyServiceWrapper>("MyServiceWrapper", client =>
{
   client.BaseAddress = new Uri("http://some_service/api");
}

to

services.AddHttpClient<IMyServiceWrapper, MyServiceWrapper>("MyServiceWrapper", client =>
{
   client.BaseAddress = new Uri("http://some_service/api");
}

in order to be able to use the interface in the constructor of my controller:

public MyController(IMyServiceWrapper myService)
{
  _myService = myService;
}

Useful for testing myController using a mock service.