[assembly: XmlConfigurator(ConfigFile = "Config/Log4Net.config", Watch = true)] //重点是这句话,读取MVC或者APILog4Net.config配置文件
namespace JWT.Common
{
 public class Log4Help
 {
  private static readonly ILog loginfo = LogManager.GetLogger("loginfo");

  private static readonly ILog logerror = LogManager.GetLogger("logerror");

  /// <summary>
  /// 打印日志信息
  /// </summary>
  /// <param name="info"></param>
  public static void Info(string info)
  {
   loginfo.Info(info);
  }

  /// <summary>
  /// 错误日志信息
  /// </summary>
  /// <param name="info"></param>
  /// <param name="ex"></param>
  public static void Error(string info, Exception ex)
  {
   logerror.Error(info, ex);
  }
 }
}

[assembly: XmlConfigurator(ConfigFile = "Log4Net.config", Watch = true)]

<"1.0" encoding="utf-8" "log4net" type="log4net.Config.Log4NetConfigurationSectionHandler,log4net" />
 </configSections>
 <log4net>
 //logerror这个名字是在帮助类中使用的
 <logger name="logerror">
  <level value="ALL" />
  <appender-ref ref="ErrorAppender" /> //ErrorAppender如下1.1
 </logger>
 <logger name="loginfo">
  <level value="ALL" />
  <appender-ref ref="InfoAppender" />
 </logger>
 
 //对应1.1名字必须一样
 <appender name="ErrorAppender" type="log4net.Appender.RollingFileAppender">
  //File用于保存路径 
  <param name="File" value="Log\\LogError\\" />
  <param name="AppendToFile" value="true" />
  <param name="MaxSizeRollBackups" value="100" />
  <param name="MaxFileSize" value="10240" />
  <param name="StaticLogFileName" value="false" />
  <param name="DatePattern" value="yyyyMMdd'.txt'" />
  <param name="RollingStyle" value="Date" />
  <layout type="log4net.Layout.PatternLayout">
  <param name="ConversionPattern" value="%d [%t] [%-5level] : %message %newline" />
  </layout>
 </appender>

 <appender name="InfoAppender" type="log4net.Appender.RollingFileAppender">
  <param name="File" value="Log\\LogInfo\\" />
  <param name="AppendToFile" value="true" />
  <param name="MaxFileSize" value="10240" />
  <param name="MaxSizeRollBackups" value="100" />
  <param name="StaticLogFileName" value="false" />
  <param name="DatePattern" value="yyyyMMdd'.txt'" />
  <param name="RollingStyle" value="Date" />
  <layout type="log4net.Layout.PatternLayout">
  <param name="ConversionPattern" value="%d [%t] [%-5level] : %message %newline" />
  </layout>
 </appender>
 </log4net>
</configuration>

 public class HomeController : Controller
 {
  public ActionResult Index()
  {
   Log4Help.Info("1111");
   Log4Help.Error("12345",null);
   return View();
  }

 }