Question

I am looking into C# logging and I do not want my log messages to spend any time processing if the message is below the logging threshold. The best I can see log4net does is a threshold check AFTER evaluating the log parameters.

Example:

_logger.Debug( "My complicated log message " + thisFunctionTakesALongTime() + " will take a long time" )

Even if the threshold is above Debug, thisFunctionTakesALongTime will still be evaluated.

In log4net you are supposed to use _logger.isDebugEnabled so you end up with

if( _logger.isDebugEnabled )
    _logger.Debug( "Much faster" )

I want to know if there is a better solution for .net logging that does not involve a check each time I want to log.

In C++ I am allowed to do

LOG_DEBUG( "My complicated log message " + thisFunctionTakesALongTime() + " will take no time" )

since my LOG_DEBUG macro does the log level check itself. This frees me to have a 1 line log message throughout my app which I greatly prefer. Anyone know of a way to replicate this behavior in C#?

Answer 1

If you can target .NET 3.5 (C# 3.0) you can use extension methods to wrap the if statements.

so you can do the equivalent “macro”:

logger.Log_Debug("Much faster");

logger.Log_Debug(() => { "My complicated log message " + thisFunctionTakesALongTime() + " will take no time" });

by wrapping the check in this method:

public class Log4NetExtensionMethods {
    // simple string wrapper
    public void Log_Debug(this log4net.ILog logger, string logMessage) {
        if(logger.isDebugEnabled) {
             logger.Debug(logMessage);
        }
    }

    // this takes a delegate so you can delay execution
    // of a function call until you've determined it's necessary
    public void Log_Debug(this log4net.ILog logger, Func<string> logMessageDelegate) {
        if(logger.isDebugEnabled) {
             logger.Debug(logMessageDelegate());
        }
    }
}