最小的log4net配置

Question

How to configure a .NET console application to use a rolling log file and be able to clear its contents when the application is running?

I am answering my own question after having gathered all the needed pieces by searching the web and going through the log4net documentation (which is quite chatty) once again. I tend to do this same job once in a year or two because surprisingly there is still no single answer covering all the requirements existing on SO.

Answer 1

a) install NuGet package log4net (currently 2.0.x)

b) add the following line to the beginning of the Start method

public static void Start(string[] args)
{
    log4net.Config.XmlConfigurator.Configure();
    ...
}

c) add the following sections to App.config

*log4net sdk documentation is quite useful when trying to figure out the meaning of all these configuration values

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <configSections>
        <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net"/>
    </configSections>
    <log4net>
        <appender name="RollingFileAppender_All" type="log4net.Appender.RollingFileAppender">
            <file value="MyApplication.log" />
            <maxSizeRollBackups value="10" />
            <maximumFileSize value="1MB" />
            <lockingModel type="log4net.Appender.FileAppender+MinimalLock" />
            <layout type="log4net.Layout.PatternLayout">
                <conversionPattern value="%date [%thread] %-5level %logger - %message %exception%newline" />
            </layout>
        </appender>
        <root>
            <level value="ALL" /> <!-- ALL, DEBUG, INFO, WARN, ERROR, FATAL, OFF -->
            <appender-ref ref="RollingFileAppender_All" />
        </root>
    </log4net>
</configuration>

d) create a logger instance and use it

using log4net;

public class SomeClass
{
    private static readonly ILog log = LogManager.GetLogger(typeof(SomeClass));

    public void DoSomething()
    {
        try
        {
            throw new InvalidOperationException("test");
        }
        catch (Exception ex)
        {
            log.Error(ex);
        }
    }
}