Using log4net without requiring it as a dependency

Logging, to me, is a basic requirement of any code I write. There's nothing more useful to track down an odd bug than being able to turn on debug logging in production, potentially filter it down to the area of interest and get some real live data. When that code is causing trouble at a customer location, this capability becomes worth its weight in gold.

And while I am a big Interface abstraction and IoC nut, logging is so fundamental to me that I do use a static logger instance in every class and just have a hard requirement for log4net. I just want this to work and not have people worry about having to inject an ILog into my classes, forcing them to think about a concern of mine. It's far less obtrusive this way, imho.

But it does mean that no matter how small and compact my code is, i suddenly tack on a ~240KB dll requirement, often several times larger than my own code. And there goes my "i don't want them to worry about a concern of mine" out the window.

Depending on log4net only when it's there

That got me thinking about how I can avoid this dependency. I knew that if my code path doesn't hit a code in a referenced DLL, the absense of the DLL does not cause a problem. Of course that means i can't even reference their interfaces.

Instead I had to create a duplicate of the log4net ILog interface and proxy my calls to it. The result is a single file, Logger.cs with the following wire-up:

internal static class Logger {

  private static readonly bool _loggingIsOff = true;

  static Logger() {
    try {
        Assembly.Load("log4net");
        _loggingIsOff = false;
    } catch {}
  }

  public static ILog CreateLog() {
    var frame = new System.Diagnostics.StackFrame(1, false);
    var type = frame.GetMethod().DeclaringType;
    return _loggingIsOff ? (ILog)new NoLog() : new Log4NetLogger(type);
  }
  ...
}

(Full code is here)

Because it's not supposed to create a dependency, it's marked internal. Yes, that means that every assembly has a copy of it, but that's really not significant in the grand scheme of things. In returns for a couple of redundant bytes, I can now do add a logger to every class simply with:

private static readonly Logger.ILog _log = Logger.CreateLog();

And if log4net is present and configured, commence the flow of debug statements. Meanwhile I can ship my code without the log4net DLL.