How to register ILogger for injection in ASP.NET MVC 6

Question

I have a ASP.NET MVC 6 (beta-4) app.

public void ConfigureServices(IServiceCollection services)
{
    // Logging
    services.AddLogging();

    // ...
}

public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerfactory)
{
    // Add the console logger.
    loggerfactory.AddConsole(minLevel: LogLevel.Warning);

    // ...
}

And I have a controller...

public class HomeController : 
    Controller
{
    ILogger _logger;

    public HomeController(ILogger logger) 
    {
        _logger = logger;
    }

    // ...
}

But when I'm not getting the service registered correctly somehow: InvalidOperationException: Unable to resolve service for type 'Microsoft.Framework.Logging.ILogger' while attempting to activate 'HomeController'.. What am I doing wrong with the registering the logger?

Solution 1

I assumed that services.AddLogging(); was doing the right thing and registering ILogger. After looking at the source (https://github.com/aspnet/Logging/blob/d874c5726e713d3eb34938f85faf7be61aae0f2a/src/Microsoft.Framework.Logging/LoggingServiceCollectionExtensions.cs) I found that it's actually registering ILogger<>. Changing the signature of ILogger to ILogger<HomeController> makes the above example work.

public class HomeController : 
    Controller
{
    ILogger<HomeController> _logger;

    public HomeController(ILogger<HomeController> logger) 
    {
        _logger = logger;
    }

    // ...
}

Thanks to @Steve for setting me on the right track to find this.

Solution 2

The services.AddLogging(); didn't worked for me, so I added these two statements to ConfigureServices:

services.AddSingleton<ILoggerFactory, LoggerFactory>();
services.AddSingleton(typeof(ILogger<>), typeof(Logger<>));

Now the DI container is happy and everything works.

Comments

[b.pell]

This works. I read they are going to alter RC2 to have <T> return whatever T is (like <AppSpecificLogger>) so you can actually get your implementation and not just the interface methods. Currently, you can put anything in there and it works, looks like it ignores it. I tested ILogger<IMemoryCache> just to test that theory and it worked.

[VisualBean]

What T is actually used for, is the logging context. - you call ILogger <T> where T would usually be the calling type., but could anything really.

[stankovski]

You can also specify ILoggerFactory as described here docs.asp.net/en/latest/fundamentals/logging.html

[Sandro Stadler]

Really the signature was the issue. This have been working for me. ILogger<HomeController>. Thanks a lot.

[Ben Humphrey]

This just saved me after a couple hours of being dumbfounded.

[Charles Burns]

@Travis You saved me a trip to the asylum.