How to Log in C# .NET with log4net : A Tutorial with Practical Example

While developing software, you will always have to keep it in your mind that your software is going to be crashed someday. And when you are about to fix the bugs, you have to have something in your hand, which will give you a hint from where to start. This is why you need the logging service to log the software’s functionalities. You can build your own library for this purpose. But, for the beginning, I will recommend you to use the assembly, ‘log4net ‘, a free assembly developed by Apache.

As the first step you need to download the log4net.dll file. You can download it either from my shared files on your right hand side bar, or from here.

Now, you need to follow the steps to develop a logging service.

·         Add the reference of log4net.dll.

·         Add a new class Named CLogger.cs in the project you want to add logging.

·         Add an Application Configuration File named App.config to your application if you do not have one.

·         Add the following code segment under <configuration>…</configuration> tag.

<?xml version=“1.0“ encoding=“utf-8“ ?> <configuration>        <configSections>               <section name=“log4net“ type=“log4net.Config.Log4NetConfigurationSectionHandler, log4net“ />        </configSections>        <log4net>               <appender name=“LogFileAppender“ type=“log4net.Appender.FileAppender“>                      <param name=“File“ value=“D:\Temp\ApplicationLog.log“ />                      <param name=“AppendToFile“ value=“true“ />                      <layout type=“log4net.Layout.PatternLayout“>                            <param name=“Header“ value=“” />                            <param name=“Footer“ value=“” />                            <param name=“ConversionPattern“ value=“%d [%t] %-5p %m%n“ />                      </layout>               </appender>               <appender name=“ConsoleAppender“ type=“log4net.Appender.ConsoleAppender“ >                      <layout type=“log4net.Layout.PatternLayout“>                            <param name=“Header“ value=“[Header]\r\n“ />                            <param name=“Footer“ value=“[Footer]\r\n“ />                            <param name=“ConversionPattern“ value=“%d [%t] %-5p %m%n“ />                      </layout>               </appender>               <root>                      <level value=“DEBUG“ />                      <appender-ref ref=“LogFileAppender“ />                      <appender-ref ref=“ConsoleAppender“ />               </root>        </log4net> </configuration>

The configuration file has included two appenders, i) Console Appender and ii) File Appender. You can use either or both. The <level> tag specify the log-level. By assigning its value to “DEBUG”, we enabled the logging service to write logs of all levels. Here is a little discussion on it.

In an earlier post, I said that utility classes should be static. Our CLogger is also a utility class. So, we are going to declare this class as a static class. But before that, we will make an enum. We can do without this enum, but it will make our program flawless.

·         Add a new class named ELogLevel.cs to your project.

·         Write the following code segment in ELogLevel.cs.

using System; using System.Collections.Generic; using System.Text;   namespace Utility {     namespace LoggingService     {         public enum ELogLevel         {             DEBUG = 1,             ERROR,             FATAL,             INFO,             WARN         }     } }

Log4Net supports five levels of logs with five methods. In the CLogger class we are going to call those methods depending on the passed parameters from the application. It is so likely that you will make a spelling mistake and the logging service will not work. This is why we are giving our service a professional touch by having this enum.

·         Now, write the following code in CLogger.cs.

using System; using System.Collections.Generic; using System.Text; using log4net; using log4net.Config; using System.Diagnostics; using System.Reflection;   namespace Utility {     namespace LoggingService     {         public static class CLogger         {             #region Members             private static readonly ILog logger = LogManager.GetLogger(typeof(CLogger));                         #endregion               #region Constructors             static CLogger()             {                 XmlConfigurator.Configure();             }             #endregion               #region Methods               public static void WriteLog(ELogLevel logLevel, String log)             {                 if (logLevel.Equals(ELogLevel.DEBUG))                 {                     logger.Debug(log);                 }                 else if (logLevel.Equals(ELogLevel.ERROR))                 {                     logger.Error(log);                 }                 else if (logLevel.Equals(ELogLevel.FATAL))                 {                     logger.Fatal(log);                 }                 else if (logLevel.Equals(ELogLevel.INFO))                 {                     logger.Info(log);                 }                 else if (logLevel.Equals(ELogLevel.WARN))                 {                     logger.Warn(log);                 }             }             #endregion         }            } }

YO! Your logging service is ready to serve. Just write logs from your application as you need.

CLogger.WriteLog(ELogLevel.DEBUG, “This is a Debug log.”); CLogger.WriteLog(ELogLevel.INFO, “This is a Information log.”); CLogger.WriteLog(ELogLevel.WARN, “This is a Warning log.”); CLogger.WriteLog(ELogLevel.ERROR, “This is a Error log.”); CLogger.WriteLog(ELogLevel.FATAL, “This is a Fatal Error log.”);

Nice work! You have created a log file for your application.Find your log file in “D:\Temp” directory. You configured this location in your configuration file, remember? If not, take a close look. In later post I will discuss about the configuration file for Log4Net. So, stay tuned.

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