I just found via Michael Flanakin's Web Log that you can use the Chainsaw tool, a GUI based log viewer from Log4J project, with the Log4Net enabled applications. Here what you need to do:
1. First download the application from the above link. It requires Java. I know it sucks. But don't be put off just yet.
2. Then in the config file of your .NET application add following appender:
<appender name="UdpAppender" type="log4net.Appender.UdpAppender">
<param name="RemoteAddress" value="127.0.0.1" />
<param name="RemotePort" value="8080" />
<layout type="log4net.Layout.XmlLayoutSchemaLog4j, log4net" />
<priority value="ALL" />
<appender-ref ref="UdpAppender" />
Note the special type of layout used to format XML messages.
3. Finally create a config file with following content:
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<param name="Port" value="8080" />
When you start Chainsaw and it asks you for configuration (Warning: no receivers defined) select the third option (Let me search for configuration file) and browse for the config file you just created.
4. Start your application and you should see your loggers added in logger tree panel on the chainsaw-log tab. You can filter to see messages only from your logger by right-clicking on it and selecting “Focus on '...' “ option from the menu.
If you can't stand running Java application on your computer the you can try the Log4Net Viewer written by Naumtsev Taras. It has far less capabilities but is sufficient for most tasks.