从类库访问日志记录功能

Question

I have a solution with two projects, my WPF application project which references the second project, a class library. The WPF application uses Caliburn.Micro. I would like some classes in the library to log messages through Caliburn.Micro's logging facility (which I've set up with log4net, but that should be irrelevant).

To see if this would work, I put the following class into my library to see if anything would show up in my log, and called it from one of my viewmodels:

public class TempClass {
    private static ILog Log = LogManager.GetLog(typeof(TempClass));

    public static void LogSomething(string something) {
        Log.Info(something);
    }
}

It didn't work.

The class library can't reference my WPF application's project because that would cause a circular reference.

What is a good solution to this problem?

EDIT

A bit of additional information that might be useful. LogManager is a static class inside Caliburn.Micro.DLL, and has a public static GetLog field:

public static Func<Type, ILog> GetLog = type => NullLogInstance;

In my bootstrapper, I'm setting that to

LogManager.GetLog = type => new Log4netLogger(type);

If I set a breakpoint in the Log4netLogger constructor, it isn't hit when the GetLog() call is made to get my ILog instance in TempClass.

Here is the implementation of Log4netLogger if it helps:

internal class Log4netLogger : ILog {
    private readonly log4net.ILog InnerLogger;

    public Log4netLogger(Type type) {
        InnerLogger = log4net.LogManager.GetLogger(type);
    }

    public void Error(Exception exception) {
        InnerLogger.Error(exception.Message, exception);
    }

    public void Info(string format, params object[] args) {
        InnerLogger.InfoFormat(format, args);
    }

    public void Warn(string format, params object[] args) {
        InnerLogger.WarnFormat(format, args);
    }
}

Answer 1

It turns out the problem was using a field initializer. I believe this was being called before my bootstrapper had the opportunity to assign another delegate to GetLog. Here is the new TempClass which works:

public class TempClass {
    private static ILog Log;

    public static void LogSomething(string something) {
        if (Log == null)
            Log = LogManager.GetLog(typeof(TempClass));

        Log.Info(something);
    }
}

Answer 2

You could use Dependency Injection to solve this problem: http://msdn.microsoft.com/en-us/library/aa973811.aspx

(You could also use ServiceLocator: http://www.martinfowler.com/articles/injection.html although, you will find mixed opinions on it. Some people like it, some say that Service Locator is evil: http://blog.ploeh.dk/2010/02/03/ServiceLocatorisanAnti-Pattern/