App.config

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
   <configSections>
       <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net"/>
  </configSections>
 

  <log4net>
    <appender name="FileAppender" type="log4net.Appender.FileAppender">
      <file value="${LOCALAPPDATA}\CalDavSynchronizer\log.txt" />
      <appendToFile value="true" />
      <lockingModel type="log4net.Appender.FileAppender+MinimalLock" />
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%date [%thread] %-5level %20-logger.%-20method - %message%newline" />
      </layout>
    </appender>
    <root>
      <level value="All" />
      <appender-ref ref="FileAppender" />
    </root>
  </log4net>
  
  <startup>
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
  </startup>

</configuration>