Can I access session state from an HTTPModule?

Question

I could really do with updating a user's session variables from within my HTTPModule, but from what I can see, it isn't possible.

UPDATE: My code is currently running inside the OnBeginRequest () event handler.

UPDATE: Following advice received so far, I tried adding this to the Init () routine in my HTTPModule:

AddHandler context.PreRequestHandlerExecute, AddressOf OnPreRequestHandlerExecute

But in my OnPreRequestHandlerExecute routine, the session state is still unavailable!

Thanks, and apologies if I'm missing something!

Answer 1

Found this over on the ASP.NET forums:

using System;
using System.Web;
using System.Web.Security;
using System.Web.SessionState;
using System.Diagnostics;

// This code demonstrates how to make session state available in HttpModule,
// regardless of requested resource.
// author: Tomasz Jastrzebski

public class MyHttpModule : IHttpModule
{
   public void Init(HttpApplication application)
   {
      application.PostAcquireRequestState += new EventHandler(Application_PostAcquireRequestState);
      application.PostMapRequestHandler += new EventHandler(Application_PostMapRequestHandler);
   }

   void Application_PostMapRequestHandler(object source, EventArgs e)
   {
      HttpApplication app = (HttpApplication)source;

      if (app.Context.Handler is IReadOnlySessionState || app.Context.Handler is IRequiresSessionState) {
         // no need to replace the current handler
         return;
      }

      // swap the current handler
      app.Context.Handler = new MyHttpHandler(app.Context.Handler);
   }

   void Application_PostAcquireRequestState(object source, EventArgs e)
   {
      HttpApplication app = (HttpApplication)source;

      MyHttpHandler resourceHttpHandler = HttpContext.Current.Handler as MyHttpHandler;

      if (resourceHttpHandler != null) {
         // set the original handler back
         HttpContext.Current.Handler = resourceHttpHandler.OriginalHandler;
      }

      // -> at this point session state should be available

      Debug.Assert(app.Session != null, "it did not work :(");
   }

   public void Dispose()
   {

   }

   // a temp handler used to force the SessionStateModule to load session state
   public class MyHttpHandler : IHttpHandler, IRequiresSessionState
   {
      internal readonly IHttpHandler OriginalHandler;

      public MyHttpHandler(IHttpHandler originalHandler)
      {
         OriginalHandler = originalHandler;
      }

      public void ProcessRequest(HttpContext context)
      {
         // do not worry, ProcessRequest() will not be called, but let's be safe
         throw new InvalidOperationException("MyHttpHandler cannot process requests.");
      }

      public bool IsReusable
      {
         // IsReusable must be set to false since class has a member!
         get { return false; }
      }
   }
}