log4net 输出到VS的Output窗口

让log4net输出到文件，只花了一分钟时间，但为了同时能在Visual studio的output窗口也同步输出，花了很多时间。一般都认为output窗口就是console，然而并不是那样的。

引用这个帖子：https://stackoverflow.com/questions/20888674/log4net-outputting-file-but-not-to-debug-window

This was driving me crazy! I was able to setup logging in node.js with log4js < 5 mins, trying to use log4net took so long because I thought the vs debug window WAS the console, so I was mistakenly using the ConsoleAppender as well once I figured out the janky xml config for log4net. 

– Jacob McKay

 Apr 1, 2016 at 22:15

所以答案就是不要用ConsoleAppender 而是要用TraceAppender。

再贴一下原贴的config：

 <log4net>
    <!--
  This writes the log information to the console window.  It only logs events
  that are at least at the INFO level (which would mean that DEBUG events are not
  captured.
  -->
    <appender name="TraceAppender" type="log4net.Appender.TraceAppender">
      <filter type="log4net.Filter.StringMatchFilter">
        <stringToMatch value="test"/>
      </filter>
      <filter type="log4net.Filter.StringMatchFilter">
        <stringToMatch value="error"/>
      </filter>
      <filter type="log4net.Filter.DenyAllFilter"/>
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%date [%thread] %level %logger - %message%newline%exception"/>
      </layout>
    </appender>
    <!--
  This stores information in the logfile.txt file.  It only captures log events
  that contain the key word test or error.
  -->
    <appender name="RollingFileAppender" type="log4net.Appender.RollingFileAppender">
      <file value="C:\TOPS\LOGFILES\logfile.txt"/>
      <appendToFile value="true"/>
      <rollingStyle value="Size"/>
      <maxSizeRollBackups value="5"/>
      <maximumFileSize value="10MB"/>
      <staticLogFileName value="true"/>
      <filter type="log4net.Filter.StringMatchFilter">
        <stringToMatch value="test"/>
      </filter>
      <filter type="log4net.Filter.StringMatchFilter">
        <stringToMatch value="error"/>
      </filter>
      <filter type="log4net.Filter.DenyAllFilter"/>
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%date [%thread] %level %logger - %message%newline%exception"/>
      </layout>
    </appender>
    <root>
      <level value="DEBUG"/>
      <appender-ref ref="RollingFileAppender"/>
      <appender-ref ref="TraceAppender"/>
    </root>
  </log4net>