Why isn't ConsoleAppender configured in app.config causing logs to write to the console?

Question

In App.Config I declare a config section for my console application:

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

And configure a ConsoleAppender:

<log4net>
  <appender name="ConsoleAppender" type="log4net.Appender.ConsoleAppender">
    <layout type="log4net.Layout.PatternLayout">
    </layout>
  </appender>
  <root>
    <level value="ALL" />
    <appender-ref ref="ConsoleAppender" />
  </root>
</log4net>

We also declare a RollingFile appender in a logging util class that's part of our standard codebase at app-startup (which is not easily modified):

        _hierarchy = (Hierarchy)LogManager.GetRepository();
        _rollingFileAppender = new RollingFileAppender();            
        ... //_rollingFileppender options

        _rollingFileAppender.ActivateOptions();
        _hierarchy.Root.AddAppender(_rollingFileAppender);
        _hierarchy.Configured = true;

When I run the application, I see log-entries are written to files as expected but nothing is written to the console.

When I inspect my ILog instance in the debugger, I see no appenders at all in Logger.Appenders but I do see the RollingFileAppender instance as the only element in Root.Appenders.

log4net is something I am used to "it just works" - is there some incompatibility having config and code add appenders, or some line I need to get LogManager to look in app.config?

Answer 1

You just got me curious and i decided to play around a bit.
First observations is: You are right.

After some google i found this this

App.config

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <configSections>
    <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" />
  </configSections>
  <log4net>
    <appender name="ConsoleAppender" type="log4net.Appender.ColoredConsoleAppender">
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%date %level [%thread] %logger{1} %username - %message%newline" />
      </layout>
      <mapping>
        <level value="WARN" />
        <foreColor value="Yellow, HighIntensity" />
      </mapping>
      <mapping>
        <level value="ERROR" />
        <foreColor value="Red, HighIntensity" />
      </mapping>
    </appender>
    <root>
      <level value="ALL" />
      <appender-ref ref="ConsoleAppender" />
    </root>
  </log4net>
  <startup> 
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.7.2" />
    </startup>
</configuration>

Setup

using log4net;
using log4net.Appender;
using log4net.Layout;
using log4net.Repository.Hierarchy;

namespace LoggerDemo
{
    public static class Program
    {
        private static readonly ILog Logger = LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);

        public static void Main(string[] args)
        {
            SetupFileAppender();
            SetupTraceAppender();
            Logger.Error("Error");
        }

        private static void SetupTraceAppender()
        {
            var patternLayout = new PatternLayout();
            patternLayout.ConversionPattern = "%date [%thread] %-5level %logger - %message%newline";
            patternLayout.ActivateOptions();

            var trace = new TraceAppender();
            trace.Layout = patternLayout;
            trace.ActivateOptions();
            var l = (Logger)Logger.Logger;
            l.AddAppender(trace);
        }

        private static void SetupFileAppender()
        {
            var patternLayout = new PatternLayout();
            patternLayout.ConversionPattern = "%date [%thread] %-5level %logger - %message%newline";
            patternLayout.ActivateOptions();

            var roller = new RollingFileAppender();
            roller.AppendToFile = true;
            roller.File = "Log.txt";
            roller.Layout = patternLayout;
            roller.MaxSizeRollBackups = 5;
            roller.RollingStyle = RollingFileAppender.RollingMode.Size;
            roller.StaticLogFileName = true;
            roller.ActivateOptions();
            var l = (Logger)Logger.Logger;
            l.AddAppender(roller);
        }
    }
}

Most Important

In your AssemblyInfo add [assembly: log4net.Config.XmlConfigurator(Watch = true)]

Result