c# 4.0 - Log4Net section in Web.Config generates Error

Question

So I am trying to set up Log4Net in my Web .NET 4.0 application. I have added the correct .dll to my project and have appended the following to my Web.Config file as starters:

<configSections>
<section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net"/>
<root>
  <level value="DEBUG" />
  <appender-ref ref="RollingLogFileAppender" />
</root>
</configSections>
 <log4net debug="true">
 <appender name="RollingLogFileAppender" type="log4net.Appender.RollingFileAppender">
  <file value="C:\TestProj\TestLog.txt" />
  <appendToFile value="true" />
  <rollingStyle value="Size" />
  <maxSizeRollBackups value="10" />
  <maximumFileSize value="10MB" />
  <staticLogFileName value="true" />
  <layout type="log4net.Layout.PatternLayout">
    <conversionPattern value="%-5p %d %5rms %-22.22c{1} %-18.18M - %m%n" />
  </layout>
 </appender>

However, if I append the "log4net" section to Web.Config, I will receive the error message

Unable to start debugging on the web server. See help for common configuration problems.....

Make sure the server is running correctly. Verify there are no syntax errors in the web.config........

NOTE I can remove all the internals of this section and leave only the declaration:

<log4net></log4net>

and I will still get the same error.

Can someone give me some pointers on how to track down this error?

Answer 1

For developers who are not sure exactly how to get started following might be a help

ConfigSections in app.config

Remember to tell your application that a library is introducing a custom configuration section are you are intended to utilize, I am not perfectly sure if it is mandatory or not but I always use it as first section within root <configuration> tag.

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

log4net config in app.config

There are quite a variety of different appenders available in log4net but I usually use RollingFileAppender so I am using the same one in this sample, you can find rest of those here.

<log4net>
    <!-- file appender -->
    <appender name="RollingFileAppender" type="log4net.Appender.RollingFileAppender">
      <file value="C:/logs/my_log_file.log"/>
      <appendToFile value="true"/>
      <rollingStyle value="Date"/>
      <maxSizeRollBackups value="30"/>
      <datePattern value=".yyyy-MM-dd"/>
      <staticLogFileName value="true"/>
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%date [%thread] %-5level %logger - %message%newline"/>
      </layout>
    </appender>
    <root>
      <level value="DEBUG"/>
      <appender-ref ref="RollingFileAppender"/>
    </root>
  </log4net>

Update AssemblyInfo.cs file

I always miss this step whenever I have to create a new project. So remember you have to tell your application to watch for XMLConfigurator to perform configuration of log4net, so following line goes at the end of AssemblyInfo.cs file:

[assembly: log4net.Config.XmlConfigurator(Watch = true)]

Get Started

Remember to include the reference of log4net.dll then use following line of code to initialize logger within a class

private static ILog log = LogManager.GetLogger(typeof(MyClass));

And at the end lets use it like following

log.Info("Hello log4net");

Happy Logging :)