Implemented IHttpModule class events does not firing, SharePoint 2010 issue

I'm developing sharepoint 2010 web appliation. I want to handle some Applicaton events (Begin_Request, End_Request, Application_Start) in manner of classic asp.net way through the using Global.asax inherited from SPHttpApplication.

I found two way to distinguish that.

The first one suggests to overload SPHttpApplication in Global class. Good idea but not suitable for me because my application is deployed to sub-site of another main site. If there is a way to get around this moment it would be a great solution!

The second one suggests to implement IHttpModule interface and register events from HttpApplication context variable. It is suitable for me and I created class library project with one class implementing this interface. I've also add special record in my web.config file:

<httpModules>
    <add name="DSModule" type="Artec.DS.HttpContext.DSModule, DSModule, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31a3567341f39f94"/>
</httpModules>

where 'Artec.DS.HttpContext' is a project name and DSModule is a class name. And after all when I'm starting debug, 'Init()' method is not called.

UPDATE

namespace Artec.DS.HttpContext
{
    public class DSModule : IHttpModule
    {
        public void Dispose()
        {
           throw new NotImplementedException();
        }

        public void Init(HttpApplication context)
        {
            System.Diagnostics.Debugger.Launch();

            ApplicationVariables.AppPath = context.Server.MapPath("/");
            NhibernateManager.Init();
            NavigationManager.Init();
        }
    }
}

First of all my web.config has wrong "type" attribute. I was confused with class name instead of assembly name. So well-formed tag is as follow:

<add name="DSModule" type="Artec.DS.HttpContext.DSModule, Artec.DS.HttpContext, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31a3567341f39f94" />

After modification of web.config system.webServer/modules (thanks to CBono) Init() was called and this is an answer on my initial question.

But now I get error: "System.Web.HttpException: Server operation is not available in this context." when trying to map server path:

context.Server.MapPath("/")

Solution

The web.config entry you have listed is appropriate if your IIS instance is version 6, or if you're running in version 7 Classic Mode.

Try also adding this to your web.config to cover IIS 7 Integrated Mode (which you're probably using):

<configuration>
  <system.webServer>
    <modules>
      <add name="DSModule" type="Artec.DS.HttpContext.DSModule, DSModule, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31a3567341f39f94"/>
    </modules>
  </system.webServer>
</configuration>

It's perfectly okay to have your HTTP Module registered in both sections.