I recently switched out log4net logging from using config files to being set up programmatically. This has resulted in the nhiberate entries getting repeated 2 or sometimes 3 times. Here's the code. It uses a string which looks something like this "logger1|debug,logger2|info"

    private void SetupLog4netLoggers()
    {
        IAppender appender = GetAppender();

        SetupRootLogger(appender);

        foreach (string logger in Loggers)
        {
            CommaStringList parts = new CommaStringList(logger, '|');
            if (parts.Count != 2)
                continue;

            AddLogger(parts[0], parts[1], appender);
        }

        log.Debug("Log4net has been setup");
    }

    private IAppender GetAppender()
    {
        RollingFileAppender appender = new RollingFileAppender();
        appender.File = LogFile;
        appender.AppendToFile = true;
        appender.MaximumFileSize = MaximumFileSize;
        appender.MaxSizeRollBackups = MaximumBackups;

        PatternLayout layout = new PatternLayout(PATTERN);
        layout.ActivateOptions();

        appender.Layout = layout;
        appender.ActivateOptions();

        return appender;
    }

    private void SetupRootLogger(IAppender appender)
    {
        Hierarchy hierarchy = (Hierarchy)LogManager.GetRepository();

        hierarchy.Root.RemoveAllAppenders();
        hierarchy.Root.AddAppender(appender);
        hierarchy.Root.Level = GetLevel(RootLevel);

        hierarchy.Configured = true;

        log.Debug("Root logger setup, level[" + RootLevel + "]");
    }

    private void AddLogger(string name, string level, IAppender appender)
    {
        Logger logger = LogManager.GetRepository().GetLogger(name)as Logger;
        if (logger == null)
            return;

        logger.Level = GetLevel(level);
        logger.Additivity = false;
        logger.RemoveAllAppenders();
        logger.AddAppender(appender);

        log.Debug("logger[" + name + "] added, level[" + level + "]");
    }

And here's an example of what we see in our logs...

2010-05-06 15:50:39,781 [1] DEBUG NHibernate.Impl.SessionImpl - running ISession.Dispose()
2010-05-06 15:50:39,781 [1] DEBUG NHibernate.Impl.SessionImpl - closing session
2010-05-06 15:50:39,781 [1] DEBUG NHibernate.AdoNet.AbstractBatcher - running BatcherImpl.Dispose(true)
2010-05-06 15:50:39,796 [1] DEBUG NHibernate.Impl.SessionImpl - running ISession.Dispose()
2010-05-06 15:50:39,796 [1] DEBUG NHibernate.Impl.SessionImpl - closing session
2010-05-06 15:50:39,796 [1] DEBUG NHibernate.AdoNet.AbstractBatcher - running BatcherImpl.Dispose(true)
2010-05-06 15:50:39,796 [1] DEBUG NHibernate.Impl.SessionImpl - running ISession.Dispose()
2010-05-06 15:50:39,796 [1] DEBUG NHibernate.Impl.SessionImpl - closing session
2010-05-06 15:50:39,796 [1] DEBUG NHibernate.AdoNet.AbstractBatcher - running BatcherImpl.Dispose(true)

Any hints welcome.