第一步先添加 section 

    <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />

    <section name="Man" type="System.Configuration.DictionarySectionHandler" />

    <!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 -->

  

   <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="http://www.mamicode.com/ALL"/>

      <appender-ref ref="SmtpAppender"/>

      <appender-ref ref="LogFileAppender" />

    </root>

    <!-- Print only messages of level DEBUG or above in the packages -->

    <logger name="WebLogger">

      <level value="http://www.mamicode.com/DEBUG"/>

    </logger>

    <appender name="LogFileAppender" type="log4net.Appender.FileAppender">

      <!--定义文件存放位置-->

      <file value="http://www.mamicode.com/App_Data/Log.txt" />

      <appendToFile value="http://www.mamicode.com/true" />

      <rollingStyle value="http://www.mamicode.com/Date" />

      <datePattern value="http://www.mamicode.com/yyyyMMdd-HH:mm:ss" />

      <layout type="log4net.Layout.PatternLayout">

        <!--输出格式-->

        <conversionPattern value="http://www.mamicode.com/记录时间：%date 线程ID:[%thread] 日志级别：%-5level 出错类：%logger property:[%property{NDC}] - 错误描述：%message%newline" />

      </layout>

    </appender>

    <appender name="SmtpAppender" type="log4net.Appender.SmtpAppender">

      <authentication value="http://www.mamicode.com/Basic" />

      <to value="http://www.mamicode.com/15188378495@163.com" />

      <from value="http://www.mamicode.com/18039334986@163.com" />

      <username value="http://www.mamicode.com/18039334986@163.com" />

      <password value="http://www.mamicode.com/912342642abc" />

      <subject value="http://www.mamicode.com/test logging message" />

      <smtpHost value="http://www.mamicode.com/smtp.163.com" />

      <bufferSize value="http://www.mamicode.com/512" />

      <lossy value="http://www.mamicode.com/true" />

      <evaluator type="log4net.Core.LevelEvaluator">

        <threshold value="http://www.mamicode.com/WARN"/>

      </evaluator>

      <layout type="log4net.Layout.PatternLayout">

        <conversionPattern value="http://www.mamicode.com/%newline%date [%thread] %-5level %logger [%property{NDC}] - %message%newline%newline%newline" />

      </layout>

    </appender>

  </log4net>