title: Log4Net can't find %username property when I name the file in my appender
body: <p>log4net doesn't do the correct <code>PatternString</code> substitution for my login name. I want my log to be </p>
  
  <blockquote>
    <p>Logs\YYYYMMDD\MSMQcore_[username].log</p>
  </blockquote>
  
  <p>When I use the <code>%username</code> property, I get the domain in the path, which adds another folder indirection in there. I only want the user name.</p>
  
  <blockquote>
    <p>Logs\YYYYMMDD\MSMQcore_[domain]\[username].log</p>
  </blockquote>
  
  <p>Anyone have an example of inserting the "username" in the appender's file name? I've tried a bunch of things, I'm still scratching my head.</p>
  
  <pre><code>&lt;appender name="core_Appender" type="log4net.Appender.RollingFileAppender" &gt;
  &lt;!-- &lt;file type="log4net.Util.PatternString"  value="Logs/%date{yyyyMMdd}/MSMQcore_%identity.log" /&gt; --&gt;
  &lt;!-- &lt;file type="log4net.Util.PatternString"  value="Logs/%date{yyyyMMdd}/MSMQcore_%property{user}.log" /&gt; --&gt;
  &lt;file type="log4net.Util.PatternString"  value="Logs/%date{yyyyMMdd}/MSMQcore_%username.log" /&gt;
  &lt;/appender&gt;
  </code></pre>