log4net: using StringMatchFilter to filter out unwanted messages

 You can use StringMatchFilter in log4net to discard unwanted messages. An example:

<log4net>

    <root>

        <appender-ref ref="ConsoleAppender"/>

    </root>

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

        <filter type="log4net.Filter.StringMatchFilter">

            <stringToMatch value="message 1"/>

            <acceptOnMatch value="false"/>

        </filter>

        <filter type="log4net.Filter.StringMatchFilter">

            <stringToMatch value="message 2"/>

            <acceptOnMatch value="false"/>

        </filter>

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

            <conversionPattern value="%d [%t] %-5p %logger - %m%n" />

        </layout>

    </appender>

</log4net>

Now in code, do this

log.Error("message 1");
log.Error("message 2");
log.Error("message 3");

Run the code

C:\Temp\log4net\console>dotnet run
2022-03-25 15:02:06,192 [1] ERROR Program - message 3

It did not log message 1 or message 2.