log4net on Windows Forms doesn't write log file

Question

I'm developing a Windows Form app with .NET Framework 4.0 and log4net 1.2.13.

This is the first time I use log4net in a Windows Form application and it doesn't work. Maybe I forget a configuration step nut now, it doesn't work: I can't find the log file.

This is how I instance logger:

public partial class MainForm : Form
{
    private static readonly log4net.ILog _logger =
        log4net.LogManager.GetLogger(typeof(MainForm));

And this is App.Config contents:

<log4net xsi:noNamespaceSchemaLocation="http://csharptest.net/downloads/schema/log4net.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <appender type="log4net.Appender.RollingFileAppender" name="AppLogErrorAppender">
    <file value="D:\\AppError.log" />
    <appendToFile value="true" />
    <rollingStyle value="Date" />
    <datePattern value=".yyyyMMdd.lo\g" />
    <maximumFileSize value="5MB" />
    <maxSizeRollBackups value="-1" />
    <countDirection value="1" />
    <layout type="log4net.Layout.PatternLayout">
      <conversionPattern value="%date %-5level [%thread] %logger - %message%newline%exception" />
    </layout>
  </appender>
  <appender name="ConsoleAppender" type="log4net.Appender.ConsoleAppender">
    <layout type="log4net.Layout.PatternLayout">
      <conversionPattern value="%date %-5level [%thread] %logger - %message%newline%exception" />
    </layout>
  </appender>
  <logger name="AppLog">
    <level value="ERROR" />
    <appender-ref ref="AppLogErrorAppender" />
  </logger>
  <root>
      <level value="ERROR" />
      <appender-ref ref="AppLogErrorAppender" />
      <appender-ref ref="ConsoleAppender" />
  </root>
</log4net>

I'm logging here:

public const string LogExceptionNameMessageFormatString = "EXCEPTION: {0} - Message: {1}";

private void LogError(string exceptionMessage, string exceptionName)
{
    _logger.ErrorFormat(LogExceptionNameMessageFormatString, exceptionName, exceptionMessage);
}

I have a breakpoint on it, and it stops.

What am I doing wrong?

Answer 1

Program.cs:

[STAThread]
private static void Main(string[] args)
{
    log4net.Config.XmlConfigurator.Configure();

    /* other stuff */
}

I will usually also Log something immediately in void Main, after configuration.

App.config:

You need to remember to put in the log4net config section as the first element of the <configSections>:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
        <configSections>
                <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net"/>
        </configSections>
        <startup>
                <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/>
        </startup>

        <log4net>
                <appender name="RollingFileAppender" type="log4net.Appender.RollingFileAppender">
                        <file value="log.log"/>
                        <appendToFile value="true"/>
                        <rollingStyle value="Size"/>
                        <maxSizeRollBackups value="1"/>
                        <maximumFileSize value="5MB"/>
                        <staticLogFileName value="true"/>
                        <layout type="log4net.Layout.PatternLayout">
                                <conversionPattern value="%newline%date [%thread] %-5level %logger - %message%newline%exception"/>
                        </layout>
                </appender>

                <appender name="DebugAppender" type="log4net.Appender.DebugAppender">
                        <immediateFlush value="true"/>
                        <layout type="log4net.Layout.PatternLayout">
                                <conversionPattern value="%newline%date [%thread] %property{detailContext} %-5level %logger - %message%newline%exception"/>
                        </layout>
                </appender>

                <root>
                        <level value="ALL"/>
                        <appender-ref ref="DebugAppender"/>
                        <appender-ref ref="RollingFileAppender"/>
                </root>
        </log4net>
</configuration>