Why is log4net not recognized in configuration file?

Question

I wrote a test console application in C# using log4net:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using log4net;
using log4net.Config;

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

namespace Log4Net_Test
{
    class Program
    {
        private static readonly ILog log = LogManager.GetLogger(typeof(Program));

        static void Main(string[] args)
        {    
            log.Info("Entering application");    
            log.Debug("Debug message");    
            log.Info("Leaving application");
        }
    }
}

My App.config file looks like this:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <startup>
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
  </startup>
  <appSettings>
    <add key="log4net.Internal.Debug" value="true"/>
  </appSettings>
  <log4net>
    <!-- A1 is set to be a ConsoleAppender -->
    <appender name="A1" type="log4net.Appender.FileAppender">
      <file value="logfile.txt" />
      <appendToFile value="false" />

      <!-- A1 uses PatternLayout -->
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%-4timestamp [%thread] %-5level %logger %ndc - %message%newline" />
      </layout>
    </appender>

    <!-- Set root logger level to DEBUG and its only appender to A1 -->
    <root>
      <level value="DEBUG" />
      <appender-ref ref="A1" />
    </root>
  </log4net>
</configuration>

Executing the test program ends up in the following error message:

log4net:ERROR Exception while reading ConfigurationSettings. Check your .config
file is well formed XML.
System.Configuration.ConfigurationErrorsException: Configuration system failed t
o initialize ---> System.Configuration.ConfigurationErrorsException: Unrecognize
d configuration section log4net.

What is wrong with my configuration file?

UPDATE 1: The configSections´ part was missing, as pointed out in the accepted answer. But I also had to remove thestartupsection, otherwise the same error appeared. I do not know why thestartup` section is causing the problem, too. Perhaps someone more experienced can tell and write a comment.

score 35 · Accepted Answer · answered Jun 14 '13 at 10:49

35

You need to add log4net also in the section block

<configSections>

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

</configSections>

answered Jun 14 '13 at 10:49

Massimiliano Peluso

26,379
6
61
70

Thank you, this section was missing. – John Threepwood Jun 14 '13 at 12:36

score 13 · Answer 2 · edited May 23 '17 at 11:47

13

The startup section needed to be removed as well because log4net does not support Framework .NET4.5

You can see my similar answer here: https://stackoverflow.com/a/13236410/1783224

Or you can see the supported frameworks in the documentation: http://logging.apache.org/log4net/release/features.html

edited May 23 '17 at 11:47

Community

1
1

answered Jun 14 '13 at 16:32

Milen Kindekov

1,903
1
23
31

6

I've got it working fine with 4.5 startup block, as long as the configSection with log4net comes before it. – nathanchere Aug 02 '13 at 10:58
2

I can confirm the fix @nathanchere suggested – tyh Dec 03 '14 at 17:14
3

This is incorrect. The Log4Net supports .NET 4.5 for sure. – sean717 Jun 01 '15 at 06:38
Current version of log4net works correctly with .NET 4.5 using the solution above – Gianpiero Nov 04 '15 at 19:03
1

Even above startup didn't solve my problem. It had to be the first child of configuration. It appears to work fine with 4.5. – Jason Eades Mar 08 '16 at 14:52

score 4 · Answer 3 · answered Nov 16 '16 at 13:35

You should also remember that section block <configSections> must be under the <configuration> otherwise will occurred an error:

Exception while reading ConfigurationSettings. Check your .config file is well formed XML.

For example:

<configuration>
  <configSections>
    <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler,log4net" />
  </configSections>   
  <!-- Log4net Logging Setup -->   
  <log4net>
    <appender name="FileAppender" type="log4net.Appender.FileAppender,log4net">
      <file value="service.log" />
      <appendToFile value="true" />
      <lockingModel type="log4net.Appender.FileAppender+MinimalLock" />
      <!--
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%date [%thread] %level %logger - %message%newline" />
      </layout>
      -->
      <layout type="log4net.Layout.PatternLayout">
        <param name="ConversionPattern" value="%date [%thread] %-5level %logger.%method - %message%newline" />
      </layout>
      <filter type="log4net.Filter.LevelRangeFilter">
        <levelMin value="INFO" />
        <levelMax value="FATAL" />
      </filter>
    </appender>
    <root>
      <level value="DEBUG" />
      <appender-ref ref="FileAppender" />
    </root>   
  </log4net>   
  <startup>
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.6.1" />
  </startup>
</configuration>

Wow - this helped me! But there is even more: The configSections-node HAS TO BE THE FIRST node under the configuration-node or else one will receive that message you mentioned. — Igor, May 01 '17 at 00:08
The comment made me think a bit - I have always had a separate file for the log4net.config - and seeing the startup at the bottom - made me move the log4net section into the app.config (I had already added a configuration section) and after moving the log4net section - it finally started working (.Net 4.6.1 project target) - not sure what changed - but now it is logging and not throwing exceptions on load. — Mark W. Mitchell, Sep 26 '20 at 15:44

Why is log4net not recognized in configuration file?

3 Answers3

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