Log4Net StringMatchFilter is not filtering anything

Question

I'm logging all SQL generated by nHibernate because we have a weird issue. This alone generates huge logs so I'm trying to shorten them up a bit by trying to only log lines that contain a certain ID. It still seems like everything is coming through. Does anything look weird here?

    <appender name="RollingFile" type="log4net.Appender.RollingFileAppender,log4net" >

        <param name="File" value="nHibernate.txt" />
        <param name="AppendToFile" value="true" />
        <param name="DatePattern" value="yyyy.MM.dd" />

        <layout type="log4net.Layout.PatternLayout,log4net">
            <conversionPattern value="%d %p %m%n" />
        </layout>

        <filter type="log4net.Filter.StringMatchFilter">
            <stringToMatch value="5764" />
            <acceptOnMatch value="true" />
        </filter>

    </appender>

    <logger name="NHibernate.SQL" additivity="false">
        <level value="DEBUG" />
        <appender-ref ref="RollingFile" />
    </logger>

Answer 1

It turns out you need to add this code:

<filter type="log4net.Filter.DenyAllFilter" />

The full block looks like this:

<appender name="RollingFile" type="log4net.Appender.RollingFileAppender,log4net">
    
    <param name="File" value="nHibernate.txt" />
    <param name="AppendToFile" value="true" />
    <param name="DatePattern" value="yyyy.MM.dd" />

    <layout type="log4net.Layout.PatternLayout,log4net">
        <conversionPattern value="%d %p %m%n" />
    </layout>

    <filter type="log4net.Filter.StringMatchFilter">
        <stringToMatch value="5764" />
        <acceptOnMatch value="true" />
    </filter>

    <!-- need this here! -->
    <filter type="log4net.Filter.DenyAllFilter" />
    
</appender>

<logger name="NHibernate.SQL" additivity="false">
    <level value="DEBUG" />
    <appender-ref ref="RollingFile" />
</logger>