A realistic log4net config

Most log4net config file examples show the simplest case.  Here is a more realistic example of a production log4net config that uses multiple appenders.  This comes from an ASP.NET application, but the same technique will work in a server or client application.  This config sets up two appenders:

  1. The first one writes all messages at DEBUG or higher to a log file.  Depending on your needs, a RollingFileAppender that creates a new file every day or week might be more appropriate.
  2. The second appender sends email messages when a new user account is created, or when an error is logged.

<?xml version="1.0"?>



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



<!-- The DebugFileAppender writes all messages to a log file-->

<appender name="DebugFileAppender" type="log4net.Appender.FileAppender">

<file value="LinkedCellsWebService.log" />

<threshold value="DEBUG" />

<appendToFile value="true" />

<layout type="log4net.Layout.PatternLayout">

<param name="ConversionPattern" value="%5p [%d] - %m%n" />



<!-- The EmailAppender sends an email when something matches the filters-->

<appender name="EmailAppender" type="log4net.Appender.SmtpAppender">

<evaluator type="log4net.Core.LevelEvaluator">

<threshold value="DEBUG"/>


<!-- The filters are processed in order:

1) match the Inserted New User message

2) match any WARN or higher messages

3) reject everything else -->

<filter type="log4net.Filter.StringMatchFilter">

<stringToMatch value="Inserted a new user" />

<acceptOnMatch value="true" />


<filter type="log4net.Filter.LevelRangeFilter">

<levelMin value="WARN" />

<acceptOnMatch value="true" />


<filter type="log4net.Filter.DenyAllFilter" />

<!-- The SmtpAppender authenticates against the mail server, the buffersize of 10 provides 10 lines

of context when an error happens. -->

<subject value="LinkedCells: Production log event" />

<to value="notifications@LinkedCells.com" />

<from value="notifications@LinkedCells.com" />

<password value ="password" />

<smtpHost value="MAILSERVER" />

<bufferSize value="10" />

<lossy value="true" />

<layout type="log4net.Layout.PatternLayout">

<param name="ConversionPattern" value="%5p [%d] - %m%n" />




<!-- add other appenders here and the log messages will be sent to every listed appender -->

<appender-ref ref="DebugFileAppender" />

<appender-ref ref="EmailAppender" />



----- END OF CONFIG -----


  • It was a time saver :)

  • is it possible to set up appenders so that one appender would log messages from one source and another from another?

  • My email is sajazbi@hotmail.com.
    I am not able to log in XML file. The following message displayed when I open the XML file:

    Cannot view XML input using XSL style sheet. Please correct the error and then click the Refresh button, or try again later.
    The operation completed successfully. Error processing resource 'file:///C:/AppLog3.xml'. Line 1, Position 363

    Following is the code in my App.Config file:

    I don't know what I am doing wrong, I would really appreciate it if you can help me to resolve this issue.


  • Hi Syed,

    I think, you don't have admin rights to create xml file on C: drive.

    I have used same config setting which you have used & its working fine.


    using System.Web.UI.WebControls.WebParts;
    using System.Xml.Linq;
    using log4net;
    using log4net.Config;
    using log4net.Layout;
    using log4net.Appender;

    public partial class SampleLogging : System.Web.UI.Page
    //Creating Object of ILog
    private static readonly ILog Logger = LogManager.GetLogger(typeof(SampleLogging));

    public SampleLogging()

    protected void Page_Load(object sender, EventArgs e)
    Logger.Debug("Logging done at Debug Level.");
    Logger.Info("Logging done at Info Level.");
    Logger.Warn("Logging done at Warn Level.");
    Logger.Error("Logging done at Error Level.");
    Logger.Fatal("Logging done at Fatal Level.");


    xml Output :

    Logging done at Debug Level.
    Logging done at Info Level.
    Logging done at Warn Level.
    Logging done at Error Level.
    Logging done at Fatal Level.

    Kaushal Patel

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