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I recently wanted to set up log4net on a project I’ve been working on and found the documentation somewhat lacking when trying to find a quick and easy setup guide.  So, once I had everything set up and working, I resolved to create one myself.

So, in less time than it takes to get a pizza delivered, here is how to quickly get log4net setup on your project.

What you’ll need:

• The log4net dll (you can find the most recent version here)
• A .Net project/solution that you’d like to add logging to (you’re on your own here)
• Access to the Assembly.cs file for said project
• Access to the app.config or web.config file for said project
• A place to store your logging files (I will be using C:\ in this example, but this is one area in which the documentation actually excels)

Implementation:

1. Place the log4net dll somewhere that you can reference it easily.  I like to keep a Libraries folder around in most of my projects to hold any 3rd party dlls, but the choice is up to you.
2. Add a reference to the dll in your project solution:
• 
  
3. Add the following code to the Assembly.cs file.  More documentation here:
// Configure log4net using the .config file
[assembly: log4net.Config.XmlConfigurator(Watch = true)]
// This will cause log4net to look for a configuration file
// called TestApp.exe.config in the application base
// directory (i.e. the directory containing TestApp.exe)
// The config file will be watched for changes.
4. Add the following section to the web/app.config file in the <configuration> node:
<configSections>
  <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" />
</configSections>
5. Create a new section in the web/app.config using log4net as the node name:
<log4net>
  <appender name="FileAppender" type="log4net.Appender.FileAppender">
    <file value="C:\logfile.txt" />
    <appendToFile value="true" />
    <layout type="log4net.Layout.PatternLayout">
      <conversionPattern value="%date [%thread] %-5level %logger [%property{NDC}] – %message%newline" />
    </layout>
  </appender>
  <root>
    <level value="DEBUG" />
    <appender-ref ref="FileAppender" />
  </root>
</log4net>
6. At the top of the class in which you want to implement logging, add the using log4net; directive.
7. Define a static logger variable at the top of your class.  Something like this will work:
private static readonly ILog log = LogManager.GetLogger(typeof(Program));
8. Start adding logging statements to your code, for example:
log.Info("Entering application.");
9. Altogether then, your class might look something like this:
using System;
using System.Collections.Generic;
using System.Text;
using log4net;

namespace log4netDemo
{
    class Program
    {
        // Define a static logger variable so that it references the name of your class
        private static readonly ILog log = LogManager.GetLogger(typeof(Program));

        static void Main(string[] args)
        {
            log.Info("Entering application.");

            for (int i = 0; i < 10; i++)
            {
                log.DebugFormat("Inside of the loop (i = {0})", i);
            }

            log.Info("Exiting application.");
        }
    }
}

10. Which would produce this output when run:
2008-05-12 19:53:28,059 [11] INFO  log4netDemo.Program [(null)] – Entering application.
2008-05-12 19:53:28,260 [11] DEBUG log4netDemo.Program [(null)] – Inside of the loop (i = 0)
2008-05-12 19:53:28,280 [11] DEBUG log4netDemo.Program [(null)] – Inside of the loop (i = 1)
2008-05-12 19:53:28,280 [11] DEBUG log4netDemo.Program [(null)] – Inside of the loop (i = 2)
2008-05-12 19:53:28,280 [11] DEBUG log4netDemo.Program [(null)] – Inside of the loop (i = 3)
2008-05-12 19:53:28,280 [11] DEBUG log4netDemo.Program [(null)] – Inside of the loop (i = 4)
2008-05-12 19:53:28,280 [11] DEBUG log4netDemo.Program [(null)] – Inside of the loop (i = 5)
2008-05-12 19:53:28,280 [11] DEBUG log4netDemo.Program [(null)] – Inside of the loop (i = 6)
2008-05-12 19:53:28,280 [11] DEBUG log4netDemo.Program [(null)] – Inside of the loop (i = 7)
2008-05-12 19:53:28,280 [11] DEBUG log4netDemo.Program [(null)] – Inside of the loop (i =
2008-05-12 19:53:28,280 [11] DEBUG log4netDemo.Program [(null)] – Inside of the loop (i = 9)
2008-05-12 19:53:28,280 [11] INFO  log4netDemo.Program [(null)] – Exiting application.

That really should be all there is to it.  Although I did find the lack of a simple, quickstart guide daunting, there is actually a lot of good documentation on the log4net site.  Particularly, if you want to use a different appender or read a more general introduction.

If you’re interested, I’ve zipped up a sample solution using the code above.  You can download it here.

This entry was posted on Monday, May 12th, 2008 at 7:04 pm and is filed under C#, Programming.You can follow any responses to this entry through the RSS 2.0 feed.You can leave a response, or trackback from your own site.