Unrecognized configuration section log4net

You need to declare the log4net section:

<configSections>
    <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" />
</configSections>

Take a closer look at the documentation which explains the necessary things to do.

<configuration>
    <configSections>
        <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler,Log4net"/>
    </configSections>
</configuration>

add to your app.config file