This is a very practical guide to start using log4net quickly. Log4net is the most common and standard tool to be used to log C# applications. This tool can write logs in log files, database log table or xml files. (There is some other ways to write logs too)
 

• 1- Download log4net from http://logging.apache.org/log4net/
• 2- In Visual Studio->WebSite->AddReference add a new reference do log4net.dll that you downloaded.
• 3- Put this in the beginning of web.config file:

    <configSections>
        <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler,Log4net"/>
    </configSections> ...

•  4- Now put this in the end of web.config file:
  

    <log4net>
        <logger name="default">
            <level value="DEBUG"/>
        </logger>
        <root>
            <level value="WARN" />
            <appender-ref ref="LogFileAppender" />
        </root>
        <appender name="LogFileAppender" type="log4net.Appender.RollingFileAppender" >
            <param name="File" value="log/log.txt" />
            <param name="AppendToFile" value="true" />
            <rollingStyle value="Size" />
            <maxSizeRollBackups value="10" />
            <maximumFileSize value="10MB" />
            <staticLogFileName value="true" />
            <layout type="log4net.Layout.PatternLayout">
                <param name="ConversionPattern" value="%-5p %d{yyyy-MM-dd hh:mm:ss} - %m%n" />
            </layout>
        </appender>
    </log4net>

this configuration creates a log file in ~/log/log.txt.

•  5- To use log4net put this as a local class variable:

   protected static readonly ILog log = LogManager.GetLogger("default");

•  6- And do this to write messages in the log file.

   log.Debug("this text will be in log file");

• 7- A very good program to read log files is called BareTail, you can find it easily.
• 8- This is an example class - Example.cs
• 9- This is all you need to start using log4net