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Posted 14 Jul 2006

How to use log4net

, 14 Jul 2006
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This article describes the basic steps to be followed for using Log4net in a web application.
Download source code - 103.9 Kb


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.


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

  • Step 3: Add below section in Web.Config file.
    	<section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" />
    <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" />
    		<level value="DEBUG" />
    		<appender-ref ref="RollingLogFileAppender" />

    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 

  • Step 4: If you want log4net to add its own diagnostics messages then add below lines in web.config file.
        <add key="log4net.Internal.Debug" value="true" />
    Add below lines after system.web section:
        <trace autoflush="true">
                <add name="textWriterTraceListener" 
                   initializeData="C:\\TestProj\\TestProjlog4net.txt" />

  • 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(
  • 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.


    • 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 India
    No Biography provided

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    Comments and Discussions

    QuestionProblem with Log4Net Pin
    Member 1102118921-Apr-15 10:18
    memberMember 1102118921-Apr-15 10:18 
    AnswerRe: Problem with Log4Net Pin
    Member 1163319322-Apr-15 5:00
    memberMember 1163319322-Apr-15 5:00 
    GeneralRe: Problem with Log4Net Pin
    Member 1102118923-Apr-15 0:59
    memberMember 1102118923-Apr-15 0:59 
    GeneralMy vote of 3 Pin
    mahi03079-Oct-14 4:20
    membermahi03079-Oct-14 4:20 
    GeneralMy vote of 5 Pin
    harsha.bhuyan21-May-13 2:49
    memberharsha.bhuyan21-May-13 2:49 
    QuestionWhere is AssemblyInfo.cs Pin
    ariftk8-Jan-13 19:43
    memberariftk8-Jan-13 19:43 
    AnswerRe: Where is AssemblyInfo.cs Pin
    Avil Mascarenhas16-Oct-14 1:26
    memberAvil Mascarenhas16-Oct-14 1:26 
    GeneralMy vote of 5 Pin
    Kiran Kumar B10-Oct-12 21:20
    memberKiran Kumar B10-Oct-12 21:20 
    QuestionRead the configuration Pin
    Haitham.Hussien17-Sep-12 3:15
    memberHaitham.Hussien17-Sep-12 3:15 
    QuestionLog4Net Pin
    sivakarthiki9-Sep-12 7:14
    membersivakarthiki9-Sep-12 7:14 
    GeneralMy vote of 4 Pin
    Member 859976627-Aug-12 23:55
    memberMember 859976627-Aug-12 23:55 
    Really Useful
    GeneralMy vote of 3 Pin
    yusia112-Jan-12 2:59
    memberyusia112-Jan-12 2:59 
    Questiongood article Pin
    ajaytiwari12345630-Sep-11 2:16
    memberajaytiwari12345630-Sep-11 2:16 
    GeneralMy vote of 2 Pin
    jalalx24-Sep-11 1:36
    memberjalalx24-Sep-11 1:36 
    GeneralMy vote of 4 Pin
    Herminio Tribaldos27-Jul-11 22:13
    memberHerminio Tribaldos27-Jul-11 22:13 
    GeneralMy vote of 4 Pin
    RiteshPapneja20-Apr-11 23:03
    memberRiteshPapneja20-Apr-11 23:03 
    GeneralNot working while executing the exe(not in debug mode) Pin
    HaroldVish27-Jan-11 20:08
    memberHaroldVish27-Jan-11 20:08 
    GeneralMy vote of 3 Pin
    Pravin Patil, Mumbai17-Jan-11 21:53
    memberPravin Patil, Mumbai17-Jan-11 21:53 
    GeneralMy vote of 1 Pin
    zeltera14-Oct-10 5:59
    memberzeltera14-Oct-10 5:59 
    GeneralMy vote of 5 Pin
    pritam hinger16-Sep-10 0:40
    memberpritam hinger16-Sep-10 0:40 
    GeneralMy vote of 5 Pin
    zippy198114-Sep-10 5:11
    memberzippy198114-Sep-10 5:11 
    GeneralLog4net in Windows service Pin
    Jitendra Zaa7-Sep-10 22:08
    memberJitendra Zaa7-Sep-10 22:08 
    GeneralNot working Pin
    ravileeladhar22-Jul-10 0:40
    memberravileeladhar22-Jul-10 0:40 
    GeneralRe: Not working Pin
    Suman Kumar23-Jul-10 4:00
    memberSuman Kumar23-Jul-10 4:00 
    GeneralFurther tutorials Pin
    Member 41098946-Apr-10 7:30
    memberMember 41098946-Apr-10 7:30 
    QuestionHow to read and parse the pattern entry from a log file? Pin
    nareshpatel17-Feb-10 22:18
    membernareshpatel17-Feb-10 22:18 
    AnswerRe: How to read and parse the pattern entry from a log file? Pin
    Suman Kumar18-Feb-10 8:43
    memberSuman Kumar18-Feb-10 8:43 
    GeneralRe: How to read and parse the pattern entry from a log file? Pin
    nareshpatel18-Feb-10 11:33
    membernareshpatel18-Feb-10 11:33 
    GeneralAnother good link for setting and implement log4net Pin
    MD.Tanvir Anowar15-Nov-09 17:18
    memberMD.Tanvir Anowar15-Nov-09 17:18 
    GeneralWeb.config slight change Pin
    Jack Choy11-May-09 10:21
    memberJack Choy11-May-09 10:21 
    Questionlog4NET Problem insert into MS SQL Server Pin
    What0589-Mar-09 13:27
    memberWhat0589-Mar-09 13:27 
    QuestionHow to use log4net in class library? Pin
    Member 221321220-Jan-09 21:59
    memberMember 221321220-Jan-09 21:59 
    GeneralTurn logging on and off Pin
    Member 385397110-Oct-08 0:26
    memberMember 385397110-Oct-08 0:26 
    AnswerRe: Turn logging on and off Pin
    Suman Kumar18-Oct-08 19:09
    memberSuman Kumar18-Oct-08 19:09 
    GeneralThank you Pin
    Alain VIZZINI27-Jul-08 21:44
    memberAlain VIZZINI27-Jul-08 21:44 
    GeneralRe: Thank you Pin
    Suman Kumar14-Sep-08 19:27
    memberSuman Kumar14-Sep-08 19:27 
    GeneralSetting header and footer in a log Pin
    jason_X22-Jul-08 10:26
    memberjason_X22-Jul-08 10:26 
    Generallog4net and SharePoint Pin
    ld52219-Jan-08 8:46
    memberld52219-Jan-08 8:46 
    QuestionIt's not working in .net 2.0 Pin
    todeti23-Oct-07 7:11
    membertodeti23-Oct-07 7:11 
    AnswerRe: It's not working in .net 2.0 Pin
    Dadou00221-Nov-07 9:04
    memberDadou00221-Nov-07 9:04 
    GeneralRe: It's not working in .net 2.0 Pin
    cse_king111-Apr-08 0:00
    membercse_king111-Apr-08 0:00 
    AnswerRe: It's not working in .net 2.0 Pin
    Jaroslav Martsek8-Jul-08 23:47
    memberJaroslav Martsek8-Jul-08 23:47 
    Questionlog4net config Pin
    Ravindra_sagar30-Sep-07 22:37
    memberRavindra_sagar30-Sep-07 22:37 
    GeneralError Pin
    Malayil alex23-Aug-07 4:17
    memberMalayil alex23-Aug-07 4:17 
    GeneralRe: Error Pin
    Suman Kumar5-Sep-07 19:17
    memberSuman Kumar5-Sep-07 19:17 
    GeneralHave you seen NLog? [modified] Pin
    Jaroslaw Kowalski17-Jul-06 5:28
    memberJaroslaw Kowalski17-Jul-06 5:28 
    GeneralRe: Have you seen NLog? Pin
    Suman Kumar20-Jul-06 20:24
    memberSuman Kumar20-Jul-06 20:24 
    Generallog4net sample Pin
    Rujith Anand16-Jul-06 22:34
    memberRujith Anand16-Jul-06 22:34 
    GeneralRe: log4net sample Pin
    Suman Kumar16-Jul-06 22:52
    memberSuman Kumar16-Jul-06 22:52 
    AnswerRe: log4net sample Pin
    Suman Kumar17-Jul-06 8:09
    memberSuman Kumar17-Jul-06 8:09 

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