Logging is an essential part of any application. Following is a simple step by step guide to integrate Log4net in your ASP.NET Web Application.

Create a new website

• open Microsoft Visual Studio 2005 or 2008, then select File - > New - > Website
• Enter your desired application path and name for the website.
• Select your preferred language ( however, in this example we will use C# )

An Illustration of adding a new Website in Microsoft Visual Studio 2008

Include Log4net in your website

• Download Log4net.
• extract the downloaded folder and look for <log4net_folder>/bin/net/2.0/Log4net.dll
• Right-Click the project name and Add a Reference to Log4net.dll

An Illustration of adding Log4net.dll to your website

Log4net configuration

• Add a config file to your project with the name log4net.config
• Copy paste the following log4net configuration settings to log4net.config file.

<?xml version="1.0" encoding="utf-8" ?>
<log4net>
	<root>
		<level value="DEBUG" />
		<appender-ref ref="RollingLogFileAppender"/>
	</root>
	<appender name="RollingFileAppender" type="log4net.Appender.RollingFileAppender">
		<file value="logsapp.log" />
		<appendToFile value="true" />
		<rollingStyle value="Size" />
		<maxSizeRollBackups value="10" />
		<maximumFileSize value="100KB" />
		<staticLogFileName value="true" />
		<layout type="log4net.Layout.PatternLayout">
			<conversionPattern value="%d [%t]%-5p %c [%x] - %m%n" />
		</layout>
	</appender>
	<appender name="RollingLogFileAppender" type="log4net.Appender.RollingFileAppender">
		<file value="logsapp.log" />
		<appendToFile value="false" />
		<datePattern value="-dddd" />
		<rollingStyle value="Date" />
		<layout type="log4net.Layout.PatternLayout">
			<conversionPattern value="%d [%t]%-5p %c [%x] - %m%n" />
		</layout>
	</appender>
</log4net>

• Create a folder logs in your project directory

An Illustration of log4net.config file

Initializing Log4net

• Add Global.asax to your project and then add the following function to it.

protected void ConfigureLogging()
{
	string logFile = HttpContext.Current.Request.PhysicalApplicationPath + "log4net.config";
	if (System.IO.File.Exists(logFile))
	{
		log4net.Config.XmlConfigurator.ConfigureAndWatch(new System.IO.FileInfo(logFile));
	}
}

• make a call to this function in Application_Start Event.

void Application_Start(object sender, EventArgs e)
{
	// Code that runs on application startup
	ConfigureLogging();
}

Logging Errors and Debugging Information

• now we are ready to log
• declare a log4net.ILog variable in your page which needs to log.

#region Logger Setup
	protected static readonly log4net.ILog log = log4net.LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);
#endregion

• Following code in Page_Load demonstrates how to log Debug Information and Errors.

#region Logger Setup
	protected static readonly log4net.ILog log = log4net.LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);
#endregion
protected void Page_Load(object sender, EventArgs e)
{
	try
	{
		log.Debug("In Page Load Function");
		log.Debug("Going to generate divide by zero");
		int a = 0;
		int b = 10 / a;
	}
	catch (Exception ex)
	{
		log.Error(ex.Message, ex);
	}
}

• Run you website and see the results in the logs folder we created earlier. It should contain the file app.log with contents like

2008-11-02 15:13:09,093 [4]DEBUG _Default [(null)] - In Page Load Function
2008-11-02 15:13:09,140 [4]DEBUG _Default [(null)] - Going to generate divide by zero
2008-11-02 15:13:09,140 [4]ERROR _Default [(null)] - Attempted to divide by zero.
System.DivideByZeroException: Attempted to divide by zero.
at _Default.Page_Load(Object sender, EventArgs e) in d:WorkTestsLoggingSampleDefault.aspx.cs:line 26

• thats it, your application is logging properly.
• VB.NET developers would need little syntax conversions.
• here is the sample code to download: Logging Sample