Log4Net: The Definitive(?) How-To for Those Who Have Already Experienced Some Degree of Frustration Trying to Set It Up the First-Time Around

by Chad Finsterwald

This code sample applies to ASP.NET for the .NET 2.0 framework. Examples are written in C#.

Contents

• Problem
• Step 1: Get Log4Net
• Step 2: Add the Right(!) Log4Net DLL to your project
• Step 3: Modify your web.config
• Step 4: Download my Log4Net Wrapper
• Step 5: Add a Global.asax file to your project
• Step 6: Log Away
• Conclusion

Problem:

There is no shortage of articles on the web showing how to set-up Log4Net, but for some reason I still find it to be an overly complicated affair. I am sure that my frustration says more about me than then about the other authors who tackled this subject. However, for those few thick-headed (and dashingly handsome) developers like me, I offer my own step-by-step (frustration free?) guide to Log4Net. As an added bonus, I also include my Log4Net wrapper, since who wants to be coupled when you can be loosely coupled?

Step 1: Get Log4Net

This is perhaps the most essential step in the process. You can find Log4Net here: Log4Net Download Page. Be sure to download the stable release! And now unzip the project to your preferred unzipping location --no judgement here.

Step 2: Add the Right(!) Log4Net DLL to your project

You will want to click through the following folders until you find the log4net.dll. (Since the wrapper is for the .NET 2.0 framework, I am assuming you want that one). Here is the click path starting from the opened unzip Log4Net folder:

Now copy the dll and bring it over to your project. I usually create a "Library" folder to hold all my referenced Dll's but put it where you want and add a reference to it. (You can add a reference by right-clicking on your web project and selecting "Add Reference". If it is still unclear to you, then perhaps the mysteries of Log4Net will have to wait until another day.) If you did that successfully you should see it under your Bin folder as shown in Image 1.

Step 3: Modify your web.config

Now open your web.config (or add one if you have not already.) You will need to add the first thing in <configuration> node. (There is an example in the sample downloadable project.):

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

You will also need to add the following section. This section is the "Appenders", i.e., it informs Log4Net how to process the logging request. Should it send to a text file, SQL Server, an email, etc? The appenders tell it what to do. This is the one clear section on the Log4Net site. (I can only surmise that the other sections are written by some misanthrope whose hatered for humanity has so warped their command of the English language as to cause grevious pain in all who dare read it.) Here is a link to the appenders config sample section. And below is the code you should add to your web.config --it too needs to be added between the <configuration> node.

<log4net>
   <root>
      <priority value="ALL" />
      <appender-ref ref="TraceAppender" />
      <appender-ref ref="ConsoleAppender" />
      <appender-ref ref="FileAppender" />
   </root>

   <appender name="TraceAppender" type="log4net.Appender.TraceAppender">
      <layout type="log4net.Layout.PatternLayout">
         <conversionPattern 
            value="%date [%thread] %-5level %logger [%property{NDC}] - %message%newline" />
      </layout>
   </appender>

   <appender name="ConsoleAppender" type="log4net.Appender.ConsoleAppender">
      <layout type="log4net.Layout.PatternLayout">
         <conversionPattern 
            value="%date [%thread] %-5level %logger [%property{NDC}] - %message%newline" />
      </layout>
   </appender>

   <appender name="FileAppender" type="log4net.Appender.FileAppender">
      <file value="c:\\Log\\log-file.txt" />
      <appendToFile value="true" />
      <lockingModel type="log4net.Appender.FileAppender+MinimalLock" />
      <layout type="log4net.Layout.PatternLayout">
         <conversionPattern 
            value="%date [%thread] %-5level %logger [%property{NDC}] - %message%newline" />
      </layout>
   </appender>
</log4net>

What these appenders have basically do is cause all logging messages to appear in the Console output --so you should see all logging messages in the output window when you debug--, to the Trace diagnostics --so you should see them if you have tracing on--, and to a file --you will need to ensure that the asp.net user has permission to create and write the log file. There are a bunch of other appenders included in Log4Net. The two most important others being the AdoNetAppender and SmtpAppender.

Step 4: Download my Log4Net Wrapper

Download the Log4Net wrapper by clicking HERE or on the "Download the Code" button at the top of this page. (Both links download a complete project, just copy over the AppLog.cs file under the App_Code directory to your App_Code directory. If you do not have an App_Code directory, add it to your project by right clicking on your web project, select "Add Asp.Net folder" and chose the "App_Code" folder.)

[Aside: Normally I would not add the AppLog class to my web project, but instead create a seperate Class Library project which is referenced by my web project. For sake of clarity, however, we will do everything in the web project.]

Step 5: Add a Global.asax file to your project

Add a global.asax file to your project by right clicking on your web project and selecting "Add New Item." From the new item dialog, choose the "Global Application Class." Once this has been added, open it and add the following to the Application_Start method

void Application_Start(object sender, EventArgs e) 
 {
   // Code that runs on application startup
   AppLog.Init();
   AppLog.Write("The Application has started... Yay me!", 
      AppLog.LogMessageType.Info, this.GetType());
 }

If you do not get intellisense when typing AppLog, then it was not correctly added to your project. If you run the project in Debug Mode, the output window should contain the following --you may need to scroll to see it.

Step 6: Log Away

I don't want to be too sanguine, but if you followed the steps above or downloaded the sample application and used it as a guide you should be position to log away to your hearts content. There is a lot more depth to the Log4Net library then I discussed here, but at least you have it running and have your sanity. Should you want a part II to this tutorial exploring the more esoteric depths of Log4Net, let me know in the comments.

Conclusion

As always, if you extend the code or the AppLog wrapper, please send me what you've done.