Simple log4net configuration

app.config

<?xml version="1.0"?>
<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="LogFileAppender" type="log4net.Appender.RollingFileAppender">
      <file value="log.log" />
      <appendToFile value="true" />
      <rollingStyle value="Size" />
      <maxSizeRollBackups value="5" />
      <maximumFileSize value="100KB" />
      <staticLogFileName value="true" />
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%date %level %logger - %message %exception%newline" />
      </layout>
    </appender>
    <root>
      <level value="ALL" />
      <appender-ref ref="LogFileAppender" />
    </root>
  </log4net>
</configuration>

ClassLogDefClip.cs

private static readonly log4net.ILog _log = log4net.LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);

Program.cs

namespace Log4NetTest
{
    class Program
    {
        static void Main(string[] args)
        {
            log4net.Config.XmlConfigurator.Configure();
        }
}

ProgrommaticConfig.cs

        private static void ConfigureLogging()
        {
            var layout = new PatternLayout("%date %level %logger - %message %exception%newline");
            layout.ActivateOptions();

            var roller = new RollingFileAppender();
            roller.Layout = layout;
            roller.AppendToFile = true;
            roller.RollingStyle = RollingFileAppender.RollingMode.Size;
            roller.MaxSizeRollBackups = 4;
            roller.MaximumFileSize = "100KB";
            roller.StaticLogFileName = true;
            roller.File = "MyLog.log";
            roller.ActivateOptions();

            var hierarchy = (Hierarchy)LogManager.GetRepository();
            hierarchy.Root.AddAppender(roller);
            hierarchy.Root.Level = Level.All;
            hierarchy.Configured = true;
        }

UnitTest.cs

string xml = @"<log4net>
                            <!-- A1 is set to be a ConsoleAppender -->
                            <appender name='Console' type='log4net.Appender.ConsoleAppender'>

                                <!-- A1 uses PatternLayout -->
                                <layout type='log4net.Layout.PatternLayout'>
                                    <conversionPattern value='%date %level %logger - %message %exception%newline' />
                                </layout>
                            </appender>

                          <appender name='RollingFile' type='log4net.Appender.RollingFileAppender'>
                            <file value='example.log' />
                            <appendToFile value='true' />
                            <maximumFileSize value='100KB' />
                            <maxSizeRollBackups value='2' />

                            <layout type='log4net.Layout.PatternLayout'>
                              <conversionPattern value='%level %thread %logger - %message%newline' />
                            </layout>
                          </appender>

                          <root>
                            <level value='DEBUG' />
                            <appender-ref ref='Console' />
                            <appender-ref ref='RollingFile' />
                          </root>

                        </log4net>";
            using (MemoryStream stream = new MemoryStream(Encoding.ASCII.GetBytes(xml)))
            {
                XmlConfigurator.Configure(stream);
            }