log4net: Error on loading custom appender

Answer 1

I would assume that the assembly cannot be found. Is the name of the assembly indeed 'HTTPAppender' and is it in the same path as the calling assembly?

Answer 2

If you are using any non standard assemblies, put them in the application directory together with your assembly. If that doesn't help, try giving your assembly a strong name and using the full name in the log4net config file. you can also try putting it into GAC.