Creates a log4Net RollingFileAppender.

dynamic-appender.cs

//  Init:  Hierarchy hierarchy = (Hierarchy)LogManager.GetRepository(); 
//          hierarchy.Root.AddAppender(CreateWSMFileAppender("logger-name-here"));
//  Usage:  var wsmLog = LogManager.GetLogger("logger-name-here");
//          if (wsmLog != null)
//          {
//              wsm.InfoFormat("Hi, you did it dynamically!");
//          {

private static IAppender CreateFileAppender(string appenderName)
{
    PatternLayout patternLayout = new PatternLayout();
    patternLayout.ConversionPattern = "%message%newline"; // message contains date/time
    patternLayout.ActivateOptions();

    RollingFileAppender appender = new RollingFileAppender();
    appender.Layout = patternLayout;
    appender.Name = appenderName;
    appender.File = appenderName +"-";
    appender.DatePattern = "yyyyMMdd'.log'";
    appender.AppendToFile = true;
    appender.RollingStyle = RollingFileAppender.RollingMode.Date;
    appender.StaticLogFileName = false;
    appender.LockingModel = new FileAppender.MinimalLock();
    appender.MaxSizeRollBackups = 7;

    var loggerMatchFilter = new log4net.Filter.LoggerMatchFilter() { LoggerToMatch = appenderName };
    var denyAllFilter = new log4net.Filter.DenyAllFilter();
    var minLevel = log4net.Core.Level.Debug;
    var levelRangeFilter = new log4net.Filter.LevelRangeFilter()
    {
        LevelMin = log4net.Core.Level.Debug,
        LevelMax = log4net.Core.Level.Fatal
    };

    appender.AddFilter(loggerMatchFilter);
    appender.AddFilter(denyAllFilter);
    appender.AddFilter(levelRangeFilter);

    appender.ActivateOptions();
    return appender;
}