How to use log4net - CodeProject®

Introduction

This article describes the basic steps to be followed for using Log4net in a web application. Log4net is an open source library that allows .NET applications to log statements to a variety of targets.

Background

This article assume you have basic working knowledge of C#, and ASP.NET programming.

Using the code

Log4net is very simple to use yet powerful logging option. This article describes log4net usage in a web application in six easy steps.

Step 1: Get the latest version of log4net library and add reference of it in your project.

Step 2: Add below line in your AssemblyInfo.cs file.

[assembly: log4net.Config.XmlConfigurator(ConfigFile="Web.config", Watch=true)]   //For log4net 1.2.10.0

Above statement provides the information about config file in which log4net configuration parameters are defined.

Step 3: Add below section in Web.Config file.

<configSections>
	<section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" />
</configSections>
	
<log4net debug="true">
	<appender name="RollingLogFileAppender" type="log4net.Appender.RollingFileAppender">
		<file value="C:\\TestProj\\TestLog.txt" />
		<appendToFile value="true" />
		<rollingStyle value="Size" />
		<maxSizeRollBackups value="10" />
		<maximumFileSize value="10MB" />
		<staticLogFileName value="true" />
		<layout type="log4net.Layout.PatternLayout">
			<conversionPattern value="%-5p %d %5rms %-22.22c{1} %-18.18M - %m%n" />
		</layout>
	</appender>
	
	<root>
		<level value="DEBUG" />
		<appender-ref ref="RollingLogFileAppender" />
	</root>
</log4net>

Above section defines the configuration parameters to be used for logging.

RollingLogFileAppender describes the appender to be used for logging. This means that the log should be written in a file, which will rollover when full. There are several other appender available and more than one appender can be attached to a logger.

The layout is responsible for formatting the logging request, whereas an appender takes care of sending the formatted output to its destination. Layout used above would format the output as below:

2006-07-14 20:26:04,033 [1736] ERROR Utility [PayStub] - Could not find a part of the path 
"c:\inetpub\wwwroot\TestProj\Template\PayStub.xml"

Step 4: If you want log4net to add its own diagnostics messages then add below lines in web.config file.

<appSettings>
    <add key="log4net.Internal.Debug" value="true" />
</appSettings>

Add below lines after system.web section:

<system.diagnostics>
    <trace autoflush="true">
        <listeners>
            <add name="textWriterTraceListener" 
               type="System.Diagnostics.TextWriterTraceListener" 
               initializeData="C:\\TestProj\\TestProjlog4net.txt" />
        </listeners>
    </trace>
</system.diagnostics>

Step 5: Now follow below steps in your code-behind.

a. Add namespace

using log4net;

b. Add below declarations within class definition

private static readonly ILog log = LogManager.GetLogger(typeof(TestPage1).Name);

private static readonly ILog log = LogManager.GetLogger(
  System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);

Step 6: Now you are ready for logging. Use below statements to log your messages in log file:

if (log.IsErrorEnabled)
{
    log.Error("Page Load failed : " + ex.Message);
}

if (log.IsDebugEnabled)
{
    log.Debug("Application loaded successfully.");
}

We have just scratched the surface of log4net. There are several other good features available in log4net and it can be used to collect vital information for several purposes. Happy Programming.

History

07/14/2006 - Article submitted.
07/19/2006 - Added Sample Project & updated the article.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

About the Author

Suman Kumar

Web Developer

India

Member

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Not working while executing the exe(not in debug mode)

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How to read and parse the pattern entry from a log file?

nareshpatel

22:18 17 Feb '10

Re: How to read and parse the pattern entry from a log file?

Suman Kumar

8:43 18 Feb '10

Re: How to read and parse the pattern entry from a log file?

nareshpatel

11:33 18 Feb '10

Another good link for setting and implement log4net

MD.Tanvir Anowar

17:18 15 Nov '09

Web.config slight change

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10:21 11 May '09

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13:27 9 Mar '09

How to use log4net in vb.net class library?

Member 2213212

21:59 20 Jan '09

Log4Net is giving proper logs when i use with Exe`s. But not with Class Libraries. I followed same steps in both exe and library. But its not writing logs in case of dll.

I followed following steps...
1. Added log4net.dll in references
2. In assemblyInfo.vb file added (<Assembly: log4net.Config.XmlConfigurator()> )
3. In class file declared (Private Shared ReadOnly log As ILog = LogManager.GetLogger("Log4NetLib"))
4. Added app.config file
5. In function i added logs like (log.Debug("..........."))

Works fine for exe but not dll.

Am i doing anything wrong? can you please advice me?

Thanks in advance
-Surya

Surya