C#: Regarding Nlog settings and usage

Question

i am curious to use nlog. i did not use it previously. so i like to use it now in my project. i have a question.

<rules>
    <logger name="SomeNamespace.Component.*" minlevel="Trace" writeTo="logfile" final="true" />
    <logger name="*" minlevel="Info" writeTo="logfile" />
</rules>

what does mean here SomeNamespace.Component.* ? show me the usage of this type of rule with sample code

what is minlevel="Info" ? what does mean minlevel here ? what other option can be set for minlevel ?

thanks

Answer 1

what does mean here SomeNamespace.Component.* ?

It means that this rule will match any loggers which have name starting with SomeNamespace.Component. . Usually name of logger equals name of class where you are creating logger (but you also can provide custom logger name):

private static readonly Logger Logger = LogManager.GetCurrentClassLogger();

So rule configuration above will match following logger names:

SomeNamespace.Component.MyClass
SomeNamespace.Component.Cool.Other.Namespace.YourClass
// etc

Ie any logger created in class from SomeNamespace.Component. namespace will match rule. No matter how many classes with loggers you have there.

what is minlevel="Info" ?

It's a minimal level of log messages which will be logged by logger.

Logger.Debug("This will not be logged");
Logger.Info("This will be logged");

NLog supports following log levels (you can use any of them to control which messages will be logged):

1. Trace
2. Debug
3. Info
4. Warn
5. Error
6. Fatal

Check description of each level at NLog wiki . Usually you should use min level Info which will log any error messages and some high-level details of what system is doing. For debugging purpose you can turn-on Trace or Debug level, but your log file can become huge very quickly. Performance also will hurt when you are writing lot of log messages.