I wrote a custom log4net appender that sends over WCF to a web-based WCF service - going to extend to allow REST'ful verbs also. We currently use log4net with file and console appenders. Anyway, at end of testing and now am told that they(dev mgmt) don't want devs to have to add reference to their Visual Studio projects to use my appender - just change the app.config file. I have a test app that, of course, has a reference to log4net as well as my WCF-based appender. The app writes to all three appenders. When I take out the reference in VS to my appender but still in app.config as the log4net docs state, my appender is not called.
Does anyone know if log4net should/can call/use my appender by just a config file entry?

Looks like it's an FAQ:

Thanks for the reply. Yes, I originally read that. That's why I'm confused that my appender is called when a reference to it is added but is NOT called without the reference even though the config file has this entry as required.

Have you tried using the appender-ref tag?

<log4net>
    <appender name="Appender1" />
    <appender name="Appender2" />
    <root>
        <appender-ref ref="Appender1" />
        <appender-ref ref="Appender2"/>
    </root>
</log4net>

Yes. That's straightforward in the documentation. I finally solved the problem. I compiled my app with the source-compiled debug version of log4net and stepped through their code. The XmlConfigurator calls ParseAppender for each appender it finds in the config file. That, in turn, calls Utils.SystemInfo.GetTypeFromString() which was exceptioning out in the else clause on Type.GetType(). It was mismatching on the Assembly with 'PUBLIC KEY TOKEN'. Took me a little while (Forest/Trees thing).
Clarification:
When you specify the assembly in the config file, the format is 'class, assembly'. Again, when I had my appender dll added as a reference in my app's Visual Studio project, there was no issue - just put the assembly name, e.g., my assembly is FooAppender.dll, with a class BarCo.FooLogger so the element in my config would be 'BarCo.FooLogger, FooAppender'
Solution:
I needed to put as much of the standard assembly specifiers as needed. So what I ended up was:
'BarCo.FooLogger, FooAppender Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'

Of course, fill in the attributes to match your actual assembly, i.e., if you have a different token or culture.

What a pain. Once again, a little bit of clarification on the documentation would go a long way in saving people time.

Btw - before anyone says 'RTM' - or even the comment above '...how .NET finds assemblies is beyond the scope of this FAQ' - I say emphatically WRONG!
It's not beyond the scope - just one line of comment/example such as:
(NOTE: The Assembly attribute can be solely the name of the DLL or a partially or fully qualified specification such as 'MyLoggerNameSpace.MyLoggerClass, MyAppender Version=1.0.0.0, Culture=neutral, PublicKeyToken=9078234009823409')

Nice, simple, there.

hi.. I'am having an error referencing a external dll.. I created a class inherited from AppenderSkeleton.. then compiled as dll...

In my test application, I specify the dll as class, assembly. But it says I have an error finding the Appender.

Do we need to create signing certificates and make it a strong name assembly? anything I am missing here?