写在前面
Log4Net是从Java的log4j移植过来的，功能也与log4j类似，可以把日志信息输出到文件、数据库、控制台、Windows 事件日志、远程系统日志服务等不同的介质或目标。
Log4Net配置选项丰富灵活，并且可在运行时动态更新配置并应用，允许同时推送到多个目标；虽然项目已经休眠了，但是该类库已久经考验，经典的设计永不过时。
获取类库
可通过NuGet获取类库，引入到项目中。
配置模板
新建log4net.xml文件，命名成log4net.config也可以，初始化时保持一致即可，配置内容如下：
<?xml version="1.0" encoding="utf-8"?>
<log4net><appender name="ConsoleAppender" type="log4net.Appender.ConsoleAppender"><layout type="log4net.Layout.PatternLayout"><conversionPattern value="%date [%thread] %-5level %logger %ndc - %message%newline" /></layout></appender><appender name="LogFileAppender" type="log4net.Appender.RollingFileAppender" LEVEL="INFO"><!--防止多线程时不能写Log,官方说线程非安全--><param name="LockingModel" type="log4net.Appender.FileAppender+MinimalLock" /><param name="File" value="Logs/" /><param name="AppendToFile" value="true"/><param name="StaticLogFileName" value="false" /><param name="DatePattern" value="yyyy-MM-dd.'info.log'" /><param name="RollingStyle" value="Date"/><param name="MaxSizeRollBackups" value="10" /><param name="MaximumFileSize" value="5MB" /><layout type="log4net.Layout.PatternLayout"><param name="ConversionPattern" value="## %d [%t] %-5p %x %m %n"/><!--<param name="ConversionPattern" value="%date [%thread] %-5level [%logger] %ndc - %message%newline" />--></layout><filter type="log4net.Filter.LevelRangeFilter"><param name="LevelMin" value="INFO" /><param name="LevelMax" value="INFO" /></filter></appender><appender name="ErrorFileAppender" type="log4net.Appender.RollingFileAppender" LEVEL="ERROR"><param name="LockingModel" type="log4net.Appender.FileAppender+MinimalLock" /><param name="File" value="Logs/" /><param name="AppendToFile" value="true"/><param name="StaticLogFileName" value="false" /><param name="DatePattern" value="yyyy-MM-dd.'error.log'" /><param name="RollingStyle" value="Date"/><param name="MaxSizeRollBackups" value="10" /><param name="MaximumFileSize" value="5MB" /><layout type="log4net.Layout.PatternLayout"><param name="ConversionPattern" value="%date [%thread] %-5level [%logger] %ndc - %message%newline" /></layout><filter type="log4net.Filter.LevelRangeFilter"><param name="LevelMin" value="WARN" /><param name="LevelMax" value="ERROR" /></filter></appender><appender name="DebugFileAppender" type="log4net.Appender.RollingFileAppender" LEVEL="ERROR"><param name="LockingModel" type="log4net.Appender.FileAppender+MinimalLock" /><param name="File" value="Logs/" /><param name="AppendToFile" value="true"/><param name="StaticLogFileName" value="false" /><param name="DatePattern" value="yyyy-MM-dd.'debug.log'" /><param name="RollingStyle" value="Date"/><param name="MaxSizeRollBackups" value="10" /><param name="MaximumFileSize" value="5MB" /><layout type="log4net.Layout.PatternLayout"><param name="ConversionPattern" value="%date [%thread] %-5level [%logger] %ndc - %message%newline" /></layout><filter type="log4net.Filter.LevelRangeFilter"><param name="LevelMin" value="DEBUG" /><param name="LevelMax" value="DEBUG" /></filter></appender><root><level value="All" /><appender-ref ref="LogFileAppender" /><appender-ref ref="ErrorFileAppender"/><appender-ref ref="DebugFileAppender" /><appender-ref ref="ConsoleAppender" /></root>
</log4net>将文件属性中的“复制到输出目录”配置为始终复制，这样配置文件会同步置执行或发布目录。
引用并初始化类库
static Program()
{//加载log4net配置log4net.Config.XmlConfigurator.ConfigureAndWatch(new FileInfo(AppDomain.CurrentDomain.BaseDirectory + @"\log4net.xml"));
}
也可以在AssemblyInfo.cs中进行初始化配置
[assembly: log4net.Config.XmlConfigurator(ConfigFile = "log4Net.xml")] 工具类
public static class LogHelper{public static void Info(object msg, params object[] parameters){var log = LogManager.GetLogger("log4netlogger");log.Info(msg);}public static void Debug(string msg){var log = LogManager.GetLogger("log4netlogger");log.Debug(msg);}public static void Error(string msg){var log = LogManager.GetLogger("log4netlogger");log.Error(msg);}public static void FormatError(string format, params object[] args){var log = LogManager.GetLogger("log4netlogger");log.Error(string.Format(format, args));}public static void Error(Exception ex){var log = LogManager.GetLogger("log4netlogger");log.Error(ex.Message, ex);}public static void Error(object msg, Exception ex){var log = LogManager.GetLogger("log4netlogger");log.Error(msg, ex);}public static void Warn(object msg, Exception ex){var log = LogManager.GetLogger("log4netlogger");log.Warn(msg, ex);}public static void Log(string msg){Info(msg);}public static void Log(Exception ex){Error(ex);}}调用示例
LogHelper.Info("事件类型出错，类型：" + _rv.EventType + "，参数：" + _rv.EventArgs);LogHelper.Debug(string.Format("action_finish：{0}", TacticsName));LogHelper.Error(string.Format("json序列化失败：{0}", json), ex);
