关于log4.net 错误，求解

1、上结果

能生成文件 ，但是文件中无内容

2、配置文件

<configSections>

<section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net"/>

</configSections>

<log4net>
   <root>
      <level value="ERROR"/>
      <appender-ref ref="SysAppender"/>
    </root>
    <!-- Print only messages of level DEBUG or above in the packages -->
    <logger name="WebLogger">
      <level value="ERROR"/>
    </logger>
    <appender name="SysAppender" type="log4net.Appender.RollingFileAppender,log4net" >
      <param name="File" value="App_Data/" />
      <param name="AppendToFile" value="true" />
      <param name="RollingStyle" value="Date" />
      <param name="DatePattern" value="&quot;Logs_&quot;yyyyMMdd&quot;.txt&quot;" />
      <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>
    <appender name="consoleApp" type="log4net.Appender.ConsoleAppender,log4net">
      <layout type="log4net.Layout.PatternLayout,log4net">
        <param name="ConversionPattern" value="%d [%t] %-5p %c - %m%n" />
      </layout>
    </appender>
  </log4net>

3、log4、net选用

4求教 为什么有文件无内容。