Log error or exception using Log4Net

Log4net is an open source Logging library for .NET Framework to log error and exception. Its one of most popular library to Log error. We will see how can we use Log4Net in our application. Below is the sample  code based on Asp.Net and C#.

To use Log4Net in your  application first download log4net library from here

Lets see step by step method to use Log4Net

Step 1) Unzip that folder and add the reference of Log4Net.dll in your application. You can find the Log4net.dll in debug folder of net (eg \incubating-log4net-1.2.10\log4net-1.2.10\bin\net\2.0\debug).

Step 2) Add this line of code in your Global.asax file under Application_Start method.

Note: if you are using Asp.Net 3.5 then you have to add manually by right click on the solution explorer "Add New Item" the add "Global Application Configuration" file.

void Application_Start(object sender, EventArgs e) 
{
log4net.Config.XmlConfigurator.Configure();
}

Step 3 ) Add this line of code in your web.config file under

<section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net"/>

Step 4 ) Add this lines of code just after

<log4net>
<appender name="LogFileAppender" type="log4net.Appender.FileAppender">
<param name="File" value="e:\Log4NetExample.log"/>
<layout type="log4net.Layout.PatternLayout">
<param name="ConversionPattern" value="%d [%t] %-5p %c %m%n"/>
layout>
appender>
<root>
<level value="All"/>
<appender-ref ref="LogFileAppender"/>
root>
log4net>

protected void btnLog4Net_Click(object sender, EventArgs e)
{
int a = 23, b=0;
try
{
int result = a / b; 
}
catch (Exception ex)
{
// Divide by Zero exception occurred and in the next line we are going to log that
ILog logger = LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);
logger.Debug(ex.Message);
}
}