如何从头开始以编程方式配置log4net(无配置)

var hierarchy = (Hierarchy)LogManager.GetRepository();
var patternLayout = new PatternLayout();
patternLayout.ConversionPattern = "%date [%thread] %-5level %logger - %message%newline";
patternLayout.ActivateOptions();

var roller = new RollingFileAppender();
roller.AppendToFile = false;
roller.File = "log.txt";
roller.Layout = patternLayout;
roller.MaxSizeRollBackups = 5;
roller.MaximumFileSize = "1GB";
roller.RollingStyle = RollingFileAppender.RollingMode.Size;
roller.StaticLogFileName = true;
roller.ActivateOptions();

hierarchy.Root.AddAppender(roller);
hierarchy.Configured = true;

var log = LogManager.GetLogger(typeof(Program));
log.Info("This is an information message");
log.Warn("This is a warning message");
log.Error("This is an error message");
log.Fatal("This is a fatal message");