Configuring log4net for ASP.NET

Yes, there are already a few posts out there, and yet I think there is value in providing just a recipe to make it work in your ASP.NET project without too many further details. So here you go (in C# where code is used):

Step 1: Download log4net, version 1.2.10 or later, and unzip the archive

Step 2: In your project add a reference to the assembly log4net.dll.

Step 3: Create a file log4net.config at the root of your project (same folder as the root web.config). The following content will log everything to the trace window, e.g. “Output” in Visual Studio:

<configuration>
   <configSections>
      <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" />
   </configSections>

   <log4net>
      <appender name="TraceAppender" type="log4net.Appender.TraceAppender" >
         <layout type="log4net.Layout.PatternLayout">
            <param name="ConversionPattern" value="%d %-5p- %m%n" />
         </layout>
      </appender>
      <root>
         <level value="ALL" />
         <appender-ref ref="TraceAppender" />
      </root>
   </log4net>
</configuration>

Step 4: In AssemblyInfo.cs add the following to make the resulting assembly aware of the configuration file:

// Tell log4net to watch the following file for modifications:
[assembly: log4net.Config.XmlConfigurator(ConfigFile = "log4net.config", Watch = true)]

Step 5: In all files in which you want to log add the following as a private member variable:

private static readonly log4net.ILog Log =
   log4net.LogManager.GetLogger(
      MethodBase.GetCurrentMethod().DeclaringType);

Step 6: Log as needed. For example for testing that steps 1 to 5 were successful, add the following in file Global.asax.cs:

public class Global : HttpApplication {
   protected void Application_Start(object sender, EventArgs e) {
      Log.Info("Application Server starting...");
   }
}

For more information about configuring log4net, e.g. logging to files, see log4net’s web site.

As always, if you find a problem with this recipe, please let me know. Happy coding!