ILogger injects fine, but kernel.Get<ILogger>() throws null ref

[jamesmanning]

This might be "by design", but off-hand it seemed a little harsh as an end-user experience.

steps:

• create new console app (happens to be .NET 4.5, but that's not likely important)

• Install-Package Ninject.Extensions.Logging.Log4net

  • the NLog and NLog2 ones are likely to do the same AFAICT

• in Main, put these 2 lines and run:

      IKernel standardKernel = new StandardKernel();
      var logger = standardKernel.Get<ILogger>();
  

throws a null ref due to Target being null (since we're asking for the instance directly, instead of having it injected into a class) in LoggerFactoryBase.GetLogger

    public ILogger GetLogger(IContext context)
    {
        return this.GetLogger(context.Request.Target.Member.DeclaringType);
    }

I'm getting a "TypeLoadException: Inheritance security rules violated by type 'Ninject.Extensions.Logging.LoggerModuleBase'" locally (unrelated to this issue AFAICT), so I haven't been able to confirm this, but a failing test for this behavior should be:

    [Fact]
    public void CanManuallyGetILoggerInstance()
    {
        using (var kernel = this.CreateKernel())
        {
            var loggerClass = kernel.Get<ILogger>();
            loggerClass.Should().NotBeNull();
            loggerClass.Type.Should().Be(typeof(ILogger));
        }
    }

Certainly a user of ninject should have ILogger injected and never need to fetch ILogger directly (service locator anti-pattern), but in trying to use the ninject logging extension with a codebase that (unfortunately) has some places fetching instances manually, this null ref keeps it from being usable.

The least-code workaround AFAICT is rebinding ILogger (currently bound in LoggerModuleBase.Load) - here's what a modified LoggerModuleBase might look like (not sure if using the service type as a fallback is really desirable or not)

    public override void Load()
    {
        //this.Bind<ILogger>().ToMethod(context => context.Kernel.Get<ILoggerFactory>().GetLogger(context));
        this.Bind<ILogger>().ToMethod(context =>
        {
            var typeForLogger = context.Request.Target != null
                                    ? context.Request.Target.Member.DeclaringType
                                    : context.Request.Service;
            return context.Kernel.Get<ILoggerFactory>().GetLogger(typeForLogger);
        });
    }

[remogloor]

The extension gets the logger name from the class it is injected into. By just getting a ILogger using Get this can't be evaluated. Use

kernel.Get<ILoggerFactory>().GetCurrentClassLogger()

instead.

https://github.com/ninject/ninject.extensions.logging/wiki/Using