ASP.NET Request Logger and Crawler Killer

Shows a simplified way to log requests and deny requests that come from <enter annoying bot name here>. Can easily be turned on or off with a database entry and without causing app recycle.

protected void Application_PreRequestHandlerExecute (object sender, EventArgs e)
        {
            RequestLogger.Logger.LogRequest(sender as HttpApplication);
        }

using System;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Text.RegularExpressions;
using System.Web;
using System.Web.Caching;

namespace RequestLogger
{
    public static class Logger
    {
        private static bool _loggingOn=true;
        private static bool _denyBots=false;
        private static string _connectionString = ConfigurationManager.AppSettings["connectionString"];

        public static void LogRequest(HttpApplication app)
        {
            HttpRequest request = app.Request;
            EnsureSwitches(app);
            if (!_loggingOn) return;
            bool isCrawler = IsCrawler(request);
            string userAgent = request.UserAgent;
            string requestPath = request.Url.AbsolutePath;
            string referer = request.UrlReferrer != null ? request.UrlReferrer.AbsolutePath : "";
            string userIp = request.UserHostAddress;
            string isCrawlerStr = isCrawler.ToString();

            SqlConnection cn = new SqlConnection(_connectionString);
            SqlCommand cmd = new SqlCommand("dbo.insertRequest", cn);
            cmd.CommandType = CommandType.StoredProcedure;
            try
            {
                cmd.Parameters.AddWithValue("@UserAgent", userAgent);
                cmd.Parameters.AddWithValue("@RequestPath", requestPath);
                cmd.Parameters.AddWithValue("@Referer", referer);
                cmd.Parameters.AddWithValue("@RemoteIp", userIp);
                cmd.Parameters.AddWithValue("@IsCrawler", isCrawlerStr);
                cn.Open();
                cmd.ExecuteNonQuery();
            }
            catch (SqlException ex)
            {
                // this is just for quick debugging, can be commented out:
                app.Response.Write(ex.Message);
            }
            finally
            {
                cn.Close();
                cmd.Dispose();
            }
            if (isCrawler && _denyBots)
                DenyAccess(app);
        }

        private static void EnsureSwitches(HttpApplication app)
        {
            if (app.Context.Cache["_loggingOn"] == null)
            {
                SqlConnection cn = new SqlConnection(_connectionString);
                SqlCommand cmd = new SqlCommand("dbo.GetRequestLogState", cn);
                cmd.CommandType = CommandType.StoredProcedure;
                cn.Open();
                SqlDataReader rdr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
                if (rdr.HasRows)
                {
                    rdr.Read();
                    _loggingOn = rdr.GetBoolean(0);
                    _denyBots = rdr.GetBoolean(1);
                }
                rdr.Close();
                cmd.Dispose();
                app.Context.Cache.Insert("_loggingOn", _loggingOn, null, DateTime.Now.AddMinutes(10),
                                         Cache.NoSlidingExpiration);
                app.Context.Cache.Insert("_denyBots", _denyBots, null, DateTime.Now.AddMinutes(10),
                                         Cache.NoSlidingExpiration);
            }
            else
            {
                _loggingOn = (bool) app.Context.Cache["_loggingOn"];
                _denyBots = (bool) app.Context.Cache["_denyBots"];
            }
        }

        private static void DenyAccess(HttpApplication app)
        {
            app.Response.StatusCode = 401;
            app.Response.StatusDescription = "Access Denied";
            app.Response.Write("401 Access Denied");
            app.CompleteRequest();
        }


        public static bool IsCrawler(HttpRequest request)
        {
            // set next line to "bool isCrawler = false; to use this to deny certain bots
            bool isCrawler = request.Browser.Crawler;
            // Microsoft doesn't properly detect several crawlers
            if (!isCrawler)
            {
                // put any additional known crawlers in the Regex below
                // you can also use this list to deny certain bots instead, if desired:
                // just set bool isCrawler = false; for first line in method 
                // and only have the ones you want to deny in the following Regex list
                Regex regEx = new Regex("Slurp|slurp|ask|Ask|Teoma|teoma");
                isCrawler = regEx.Match(request.UserAgent).Success;
            }
            return isCrawler;
        }
    }
}