title: How to specify common application data folder for log4net?
body: <p>I want log4net to write log files (using RollingFileAppender) to a subfolder of the common application data folder (e.g. C:\Documents and Settings\All Users\Application Data\Company\Product\Logs).<br>
  However, on Win XP, there is no environment variable that specifies this folder. We have <code>%ALLUSERSPROFILE%</code>, we have <code>%APPDATA%</code>, but there is nothing like <code>%ALLUSERSAPPDATA%</code>.<br>
  Programatically, I could use <code>Environment.SpecialFolder.CommonApplicationData</code>, but I need to put it in the log4net config, something like this:  </p>
  
  <pre><code>&lt;appender name="RollingFileAppender" type="log4net.Appender.RollingFileAppender"&gt;
     &lt;file value="%ALLUSERSAPPDATA%\Company\Product\Logs\error.log" /&gt;
  &lt;/appender&gt;
  </code></pre>
  
  <p>OK, we could define this in our setup, but maybe someone comes up with a better idea?</p>