log4net set from an external config file not working

Question

I'm having a weird issue with log4net.

In an ASP.NET application, I want to configure log4net externally, so I have a separate log4net.config file which I hook up to my web app with this line in the AssemblyInfo.cs file belonging to my web app:

[assembly: log4net.Config.XmlConfigurator(ConfigFile = "Log4Net.config", Watch = true)]

Now, if I instantiate the log4net logger class the normal way like this:

public class MyClass
{
    private static readonly ILog _logger = log4net.LogManager.GetLogger(typeof(MyClass));
    ....

Then this works, and the logging works as normal. However, I've wrapped my logging code in a LogManager class, which is part of a separate assembly (Infrastructure), and is reused across a number of projects. It has a GetLogger that looks like this:

public static class LogManager
{
    public static ILog GetLogger()
    {
        var stack = new StackTrace();
        var frame = stack.GetFrame(1);
        return new log4net.LogManager.GetLogger(frame.GetMethod().DeclaringType);
    }
}

So I can use this in my asp.net code:

public class MyClass
{
    private static readonly ILog _logger = LogManager.GetLogger();
    ....

But... This doesn't work! No logging is produced It doesn't seem to hook up the config file correctly. If I put my log4net config directly into the web.config, then this LogManager works fine.

Answer 1

To sum up what Bibhu has said. It has all to do with log4net.Config.XmlConfigurator .

You have to configure log4net before logging will start. So whenever you use your LogManager class the hosting application (windows, web) must configure the logging.

Either that or you need to do it in your LogManager.

Answer 2

Tell the application to configure log4net using external config file. There are really two spots for this. First, the global.asax and second the assemblyInfo.cs file. Note, that most of the time you will start out with a global.asax file with all of the code inline. For whatever reason, the only way I could get this to work was to break the global.asax up to use a code-behind and then ass the assemblyInfo.cs file. So it ends up looking like this.

global.asax:

<%@ Application Language="C#" Inherits="GlobalAsax" %>

global.asax.cs (in your App_Code folder):

using System;
using System.Web;

public class GlobalAsax : HttpApplication
{
    // you may have lots of other code here
    void Application_Start(object sender, EventArgs e)
    {
        log4net.Config.XmlConfigurator.Configure();
    }
}

Now that you have your application calling log4net's configuration, you can set an attribute in your assembly info so that log4net knows where to look for the configuration file.

AssemblyInfo.cs (in your App_Code folder):

[assembly: log4net.Config.XmlConfigurator(ConfigFile = "log4net.config", Watch = true)]

The watch flag tells log4net to keep an eye on the configuration file for potential changes. This is helpful if you want to change the configuration from logging everthing to errors only during the middle of your testing.

Then, start logging.