log4net on asp.net core

Question

I have an asp.net core 2.2 solution. The structure looks like MyProject MyProject.Web

everything is inside MyProject project and I just keep web for declarations.

I have added the Microsoft.Extensions.Logging.Log4Net.AspNetCore reference to MyProject.Web I have added loggerFactory.AddLog4Net(); in the Startup.cs. I have also added log4net.config in the MyProject.Web and set to Always Copy . I have a service in MyProject project call ServiceA

public class ServiceA
    {
        private readonly ILogger logger;

        public ServiceA(ILogger logger)
        {
            this.logger = logger;
        }
    }

However when I run the solution it crashes with error HTTP Error 500.30 - ANCM In-Process Start Failure . When I remove ILogger from constructor of ServiceA the project runs. Anything else I am missing here?

Answer 1

You should inject a strongly-typed logger instead :

public class ServiceA
{
    private readonly ILogger logger;

    public ServiceA(ILogger<ServiceA> logger)
    {
        this.logger = logger;
    }
}

This is the simple scenario shown in the documentation too . The docs show that the target type is used as the category name for the logger :

Get an ILogger object from DI.

Using a controller's type name as

I've made the same mistake from time to time, but I can't remember what the exception is. If I remember correctly, it's that the DI container can't find an ILogger instance. Which makes sense, since the extensions register a strongly typed logger . The source code for AddLogging contains this line:

services.TryAdd(ServiceDescriptor.Singleton(typeof(ILogger<>), typeof(Logger<>)));

As the ILogger< TCategoryName> docs explain, this is used to create named loggers based on a type name instead of a string:

A generic interface for logging where the category name is derived from the specified TCategoryName type name. Generally used to enable activation of a named ILogger from dependency injection.)

Answer 2

You need to inject like this

public class HomeController : Controller
    {
        private readonly IQueueService _queueService;
        private readonly ILogger<HomeController> _logger;

        public HomeController(
            IQueueService queueService,
            ILogger<HomeController> logger)
        {
            _queueService = queueService;
            _logger = logger;
        }

        [HttpGet]
        public IActionResult Index()
        {
            return View();
        }
    }

Please let me know if you still have problem