Using log4net to show NHibernate SQL in Visual Studio

I’m currently developing a web application in ASP.NET MVC and NHibernate. Since the application was very slow at some points I wanted to know which SQL queries NHibernate was executing. Since the log4net library was already included in the application I searched for a solution to output the SQL queries to the console in Visual Studio 2010 using log4net. I found the solution on this wiki and this blog post.

First thing you need to do is add a log4net section in your web.config if you don’t have one yet.

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

Then add the log4net section, and configure an appender and logger.

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

 <logger name="NHibernate.SQL" additivity="false">
 <level value="DEBUG"/>
 <appender-ref ref="DebugSQL" />
 </logger>
</log4net>

That’s all. Don’t forget to configure log4net in the Global.asax.

protected void Application_Start()
{
 log4net.Config.XmlConfigurator.Configure();
 ...
}