IHttpModule.BeginRequest firing 2X, Application_BeginRequest firing 1X

Question

I'm running VS 2008 and .NET 3.5 SP1.

I want to implement hit tracking in an HttpModule in my ASP.NET app. Pretty simple, I thought. However, the BeginRequest event of my HttpModule is firing twice for each page hit. The site is very simple right now...no security, just a bit of database work. Should log one row per page hit. Why is this event firing twice?

Moreover, IHttpModule.BeginRequest actually fires a different number of times for the first page hit when running for the first time (from a closed web browser)...3 times when I'm hitting the DB to provide dynamic data for the page, and only 1 time for pages where the DB isn't hit. It fires 2 times for every page hit after the first one, regardless of whether or not I'm touching the DB.

It's interesting to note that Application_BeginRequest (in Global.asax) is always firing only once.

Here's the code:

using System;
using System.Data;
using System.Data.Common;
using System.Net;
using System.Web;
using BluHeron.BusinessLayer;
using Microsoft.Practices.EnterpriseLibrary.Data.Sql;

namespace BluHeron.HttpModules
{
    public class SiteUsageModule : IHttpModule
    {
        public void Init(HttpApplication httpApp)
        {
            httpApp.BeginRequest += OnBeginRequest;
        }

        static void OnBeginRequest(object sender, EventArgs a)
        {
            UsageLogger.LogSiteUsage(((HttpApplication)sender).Context.Request);
        }

        public void Dispose()
        { }
    }

    public static class UsageLogger
    {
        public static void LogSiteUsage(HttpRequest r)
        {
            string ipAddress = GetHostAddress(Dns.GetHostAddresses(Dns.GetHostName()));
            string browserVersion = r.Browser.Type;

            string[] urlChunks = r.RawUrl.Split('/');
            string page = urlChunks[urlChunks.GetLength(0)-1];

            SqlDatabase db = new SqlDatabase(Common.GetConnectionString());
            DbCommand cmd = db.GetStoredProcCommand("LogUsage");

            db.AddInParameter(cmd, "IPAddress", SqlDbType.NVarChar, ipAddress);
            db.AddInParameter(cmd, "BrowserVersion", SqlDbType.NVarChar, browserVersion);
            db.AddInParameter(cmd, "PageName", SqlDbType.NVarChar, page);
            db.AddInParameter(cmd, "Notes", SqlDbType.NVarChar, "");

            db.ExecuteNonQuery(cmd);
        }

        private static string GetHostAddress(IPAddress[] addresses)
        {
            foreach (IPAddress ip in addresses)
            {
                if (ip.ToString().Length <= 15)
                {
                    return ip.ToString();
                }
            }

            return "";
        }
    }
}

Answer 1

This might be too late for the answer but can be useful for someone else. I faced with the same problem. BeginRequest event triggered for twice for each request. I debugged the code and realized that the first trigger for actual resource request but the second is result of "favicon.ico" request. At the beginning of BeginRequest event, a simple check for favicon.ico request eliminates second execution of the method.

public void Application_BeginRequest(object sender, EventArgs e) {
   HttpApplication app = (HttpApplication)sender;
   HttpContext ctx = app.Context;

   if (ctx.Request.Path == "/favicon.ico") { return; }