using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Web;
using System.Text.RegularExpressions;

namespace MyMook
{
    public class MyHttpModule : IHttpModule
    {
        public void Dispose()
        {
        }

        public void Init(HttpApplication application)
        {
            application.AcquireRequestState += new EventHandler(context_AcquireRequestState);
           // application.BeginRequest += new EventHandler(context_AcquireRequestState);
          //這裡面要注意千萬不要寫成BeginRequest，那樣就會無法獲得session
        }

        void context_AcquireRequestState(Object source, EventArgs e)
        {
            HttpApplication application = (HttpApplication)source;
            HttpContext context = application.Context;
            string path=context.Request.Path;
            if (!context.Request.CurrentExecutionFilePathExtension.Equals(".aspx") && !context.Request.CurrentExecutionFilePathExtension.Equals(".ashx") ) {
                return;
            }//此處保證只過濾aspx/ashx/htm的請求
            Match m = Regex.Match(path,@"/WebLogin/+");
            if (m.Success) {
                return;
            }//不過濾資料夾WebLogin中的內容
            try
            {
                object user = context.Session["user"];
                if (user == null)
                {
                    context.Response.Redirect("~/WebLogin/Login.aspx");
                }
                else {
                    return;
                }
            }
            catch {
                context.Response.Redirect("~/WebLogin/Login.aspx");
            }
        }

        } 
    }
 

      <httpModules>
          <add  name="MyHttpModule" type="MyMook.MyHttpModule,MyMook"/>
      </httpModules>

要點：

1.註冊事件時，不要寫application.BeginRequest，這樣會導致無法獲得Session.

         application.AcquireRequestState += new EventHandler(context_AcquireRequestState);
           // application.BeginRequest += new EventHandler(context_AcquireRequestState);