log4net下载地址 http://logging.apache.org/log4net/download_log4net.cgi
log4net-1.2.13-bin-newkey.zip(编译好的dll文件)
第1步,新建全局配置文件log4net.config,以每天日期格式分割日志文件
<?xml version="1.0"?>
<configuration>
<configSections>
<section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler,log4net" />
</configSections>
<log4net>
<!-- OFF, FATAL, ERROR, WARN, INFO, DEBUG, ALL -->
<!-- Set root logger level to ERROR and its appenders -->
<root>
<level value="ALL"/>
<appender-ref ref="SysAppender"/>
</root>
<!-- Print only messages of level DEBUG or above in the packages -->
<logger name="WebLogger">
<level value="ALL"/>
</logger>
<appender name="SysAppender" type="log4net.Appender.RollingFileAppender,log4net" >
<param name="File" value="Logger/" />
<param name="AppendToFile" value="true" />
<param name="RollingStyle" value="Date" />
<param name="DatePattern" value=""Logs_"yyyyMMdd".txt"" />
<param name="StaticLogFileName" value="false" />
<layout type="log4net.Layout.PatternLayout,log4net">
<param name="ConversionPattern" value="%d [%t] %-5p %c - %m%n" />
<param name="Header" value="
----------------------header--------------------------
" />
<param name="Footer" value="
----------------------footer--------------------------
" />
</layout>
</appender>
</log4net>
</configuration>
第2步,web.config里<configuration>下添加这一行
<configSections> <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler,log4net" /> </configSections>
第3步,Properties目录下AssemblyInfo.cs

加上这一句[assembly: log4net.Config.XmlConfigurator(ConfigFile = "log4net.config", ConfigFileExtension = "config", Watch = true)]

第4步,新建一个loghelp类
public class logHelper
{
private static readonly log4net.ILog log = log4net.LogManager.GetLogger("WebLogger");
public logHelper()
{
}
private static void SetConfig()
{
object o = ConfigurationManager.GetSection("log4net");
log4net.Config.XmlConfigurator.Configure(o as System.Xml.XmlElement);
}
public static void LogInfo(string Message)
{
if (!log.IsInfoEnabled)
SetConfig();
log.Info(Message);
}
public static void LogInfo(string Message, Exception ex)
{
if (!log.IsInfoEnabled)
SetConfig();
log.Info(Message, ex);
}
public static void ErrorInfo(string Message)
{
if (!log.IsInfoEnabled)
SetConfig();
log.Error(Message);
}
public static void DebugInfo(string Message)
{
if (!log.IsInfoEnabled)
SetConfig();
log.Debug(Message);
}
}
第5步调用代码
logHelper.LogInfo("第"+sys.count+"步"+"用户名:" + UserInfo.UserName + "修改用户信息");
第6步根据业务对日志文件进行分析(图片来自百度)

第7步
感谢 http://www.cnblogs.com/yeminglong/archive/2013/05/21/3091192.html
http://zhoufoxcn.blog.51cto.com/792419/429988/