使用log4net-1.2.0-beta8
在项目的AssemblyInfo.cs文件中设置

[assembly: log4net.Config.DOMConfiguratorAttribute(Watch=true)]
添加并编辑项目配置文件（默认为App.config），内容如下：

<?xml version="1.0" encoding="utf-8" ?> <configuration>  <configSections>   <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net"/>  </configSections>  <log4net>   <appender name="stdout" type="log4net.Appender.ConsoleAppender" >    <layout type="log4net.Layout.PatternLayout">     <!--conversionPattern value="[%d %l] %n%m%n" /-->     <param name="ConversionPattern" value="[%d %l] %m%n" />    </layout>   </appender>   <appender name="file" type="log4net.Appender.FileAppender">    <param name="File" value="log.txt" />    <param name="AppendToFile" value="true" />    <layout type="log4net.Layout.PatternLayout">     <param name="ConversionPattern" value="[%d %l] %m%n" />    </layout>   </appender>   <root>    <level value="ALL" />    <appender-ref ref="stdout" />    <appender-ref ref="file" />   </root>      <logger name="*">    <level value="ALL" />    <appender-ref ref="stdout" />    <appender-ref ref="file" />   </logger>  </log4net> </configuration>

程序代码中使用如下语句
...
using log4net;
using log4net.Config;
...
private static ILog log = LogManager.GetLogger(typeof(TestClass));
...
log.Info("This is a test!");

ok!收工