Answer by Sibeesh Venu for Unable to resolve service for type 'System.Net.Http.HttpClient'

I was getting a similar error in my Azure Function Version 2. As per this document, we should be able to add the IHttpClientFactory as a dependency. After adding this DI in my Azure Function, I was getting the error mentioned below.

Microsoft.Extensions.DependencyInjection.Abstractions: Unable to resolve service for type 'System.Net.Http.IHttpClientFactory' while attempting to activate 'OServiceBus.Adapter.FetchDataFromSubscription1'

The issue was that I had not override the Configure function to add the HttpClient as a registered dependency. So I just created a class called Statup in the root directory of my Azure Function as follows.

using Microsoft.Azure.Functions.Extensions.DependencyInjection; using Microsoft.Extensions.DependencyInjection;

[assembly: FunctionsStartup(typeof(ServiceBus.Adapter.Startup))]
namespace ServiceBus.Adapter {
    public class Startup: FunctionsStartup {
        public override void Configure(IFunctionsHostBuilder builder) {
            builder.Services.AddHttpClient();
        }
    }
}

After adding this, my function started working properly. Hope it helps.