log4net: Configure to ignore messages from a specific class

A filter certainly works but I would prefer to turn off the logger (or logger hierarchy) directly like this:

<logger name="YourNameSpace.WithNoLogging" additivity="false">
    <level value="OFF" />        
</logger>
<logger name="MyClass" additivity="false">
    <level value="OFF" />        
</logger>
<root>
    <level value="ALL" />
    <appender-ref ref="YourAppender" />
</root>

Assuming that YourNameSpace.WithNoLogging is a namespace then the shown configuration would disable logging on the entire name space. The second "example" turns off logging for your class (according to your question).

I would suggest using Filters as well. However, since I struggled finding the whole picture when I was trying to implement the filter I am posting a sample snippet of the Configutation file I created which points out where filters go.

The filter you are going for in this case would be

log4net.Filter.LoggerMatchFilter ----(Matches against a the start of the logger name.)

Hint: In the config file for Log4Net it is important where you put your tags and the priority of them actually matters. So in this case <filter> tag comes after the <appender>opening tag and before it's <file value = ... /> tag.

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <configSections>
        <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" />
    </configSections>
    <log4net>
        <appender name="RollingFile.PassedDevices" type="log4net.Appender.RollingFileAppender">
            <filter type="log4net.Filter.LoggerMatchFilter">
                <loggerToMatch value="Foo.namespace.bar.mySubclass" />
                <acceptOnMatch value="false" />
            </filter>
            <file value="myPassedDevices.log" />
            <appendToFile value="true" />
            <maximumFileSize value="100KB" />
            <maxSizeRollBackups value="2" />
            <layout type="log4net.Layout.PatternLayout">
                <conversionPattern value="%timestamp    %level  - %message  [%thread]       %logger%newline" />
            </layout>
        </appender>
        <root>
            <level value="DEBUG" />
            <appender-ref ref="RollingFile" /> <!-- My other appender which logs all and I cut it out in this snippet. Remember that you should reference all your appenders in this tag to make them work.-->
            <appender-ref ref="RollingFile.PassedDevices" />
        </root>
    </log4net>
</configuration>

In this technique you can have multiple appenders which you can redirect the logging results of a specific logger to a separate appender instead of ignoring them. Such as one appender for all logs and one for the filtered out logs for a specific class.

Sure, use a filter.

Here's the snippet posted on the blog, for future reference - all credit to the author of that blog post:

<filter type="log4net.Filter.LoggerMatchFilter">
  <!-- allows this sub-namespace to be logged... -->
  <loggerToMatch value="Noisy.Namespace.But.Important" />
</filter>
<filter type="log4net.Filter.LoggerMatchFilter">
  <!-- ...but not the rest of it -->
  <loggerToMatch value="Noisy.Namespace" />
  <acceptOnMatch value="false" />
</filter>