Log4net appender threshold not working

Question

Ive set up a logfileAppender and a consoleAppender in my log4net config for my application. I would like the logfile appender to only write ERROR messages and above and the console appender to write DEBUG and above.

my config is

<log4net debug="false">


<appender name="LogFileAppender" type="log4net.Appender.FileAppender,log4net" >
  <param name="File" value="log.txt" />
  <param name="AppendToFile" value="true" />
  <layout type="log4net.Layout.PatternLayout,log4net">
    <param name="ConversionPattern" value="%d %M - %m%n" />
  </layout>
  <threshold value="ERROR"/>
</appender>

<appender name="ConsoleAppender" type="log4net.Appender.ConsoleAppender"   >
  <layout type="log4net.Layout.PatternLayout">
    <param name="ConversionPattern" value="%d %m%n" />
  </layout>
</appender>


<root>
  <priority value="DEBUG" />
  <appender-ref ref="ConsoleAppender" />
  <appender-ref ref="LogFileAppender" />
</root>

Im finding that both ERROR and DEBUG is being output to my logfile appender. How to restrict it to only ERROR???

Answer 1

To get very specific filtering for an appender, you need to configure a LevelMatchFilter or a LevelRangeFilter for the logfile appender to filter the events which are actually output. For example:

<filter type="log4net.Filter.LevelRangeFilter">
    <levelMin value="ERROR"/>
    <levelMax value="FATAL"/>
</filter>

or

<filter type="log4net.Filter.LevelMatchFilter">
    <levelToMatch value="ERROR"/>
</filter>

put one of these inside your <appender> tag, and this should work for you:

<appender name="LogFileAppender" type="log4net.Appender.FileAppender,log4net" >
    <filter type="log4net.Filter.LevelMatchFilter">
        <levelToMatch value="ERROR"/>
    </filter>
    <param name="File" value="log.txt" />
    <param name="AppendToFile" value="true" />
    <layout type="log4net.Layout.PatternLayout,log4net">
        <param name="ConversionPattern" value="%d %M - %m%n" />
    </layout>
    <threshold value="ERROR"/>
</appender>

Note: Updated to remove mistake pointed out by kgiannakakis.

Answer 2

You need to use additivity property. See here for an example. You need to define two loggers.