我在们使用ASP.Net开发WEB网站时，有的时候是不让同一个用户名在同一时间进行多次登陆的。 为了不影响原来的整个网站，我选择使用了HttpModuler来实现。 先让所有的Page从自己的Page类：
我在们使用ASP.Net开发WEB网站时，有的时候是不让同一个用户名在同一时间进行多次登陆的。 为了不影响原来的整个网站，我选择使用了HttpModuler来实现。 先让所有的Page从自己的Page类：BasePage类继承，并实现 ISigleLogin接口。相关代码如下：
public interface ISingleLogin { string SigleUserLoginId { get; } void SigleUserLogout(); }BasePage类：public class BasePage : System.Web.UI.Page , BNet.Web.Modulers.ISingleLogin{ public BasePage() { // // TODO: 在此处添加构造函数逻辑 // } protected override void OnLoad(EventArgs e) { base.OnLoad(e); if (Session["UserId"] == null) { Response.Write("你还没有登陆"); Response.Redirect("login.aspx"); } } #region ISingleLogin 成员 public string SigleUserLoginId { get { if (Session["UserId"] != null) { return Session["UserId"].ToString(); } else return ""; } } public void SigleUserLogout() { Session.Abandon(); Response.Write("你在别处已经登陆，强制退出本次登陆!"); } #endregion}然后在Web.config中加入HttpModuler：
"SingleLogin" type= "BNet.Web.Modulers.SingleLoginModuler"/>
相关的SigleLoginModuler代码如下：
using System;using System.Collections.Generic;using System.Data;using System.Configuration;using System.Web;using System.Web.UI;namespace BNet.Web.Modulers{ /// SingleLoginModuler 的摘要说明 /// public class SingleLoginModuler : System.Web.IHttpModule { const string sigle_login_userid = "evlon_siglelogin_userid"; const string sigle_pre_logout_sessionid = "evlon_sigle_pre_logout_sessionid"; public static StringLifeValueDictionary UsableGetter(ref StringLifeValueDictionary dic) { if (dic == null) { dic = new StringLifeValueDictionary(); } else { List<string> listRemove = new List<string>(); StringLifeValueDictionary.Enumerator iter = dic.GetEnumerator(); while (iter.MoveNext()) { if (iter.Current.Value.life < DateTime.Now) { listRemove.Add(iter.Current.Key); } } foreach (string key in listRemove) { dic.Remove(key); } } return dic; } static StringLifeValueDictionary loginedUserIdDictionary = null; static StringLifeValueDictionary LoginedUserIdDictionary { get { return UsableGetter(ref loginedUserIdDictionary); } } static StringLifeValueDictionary preLogoutSessionIdDictionary = null; static StringLifeValueDictionary PreLogoutSessionIdDictionary { get { return UsableGetter(ref preLogoutSessionIdDictionary); } } public SingleLoginModuler() { // // TODO: 在此处添加构造函数逻辑 // } #region IHttpModule 成员 public void Dispose() { } public void Init(HttpApplication context) { context.PreRequestHandlerExecute += new EventHandler(context_PreRequestHandlerExecute); context.PostRequestHandlerExecute += new EventHandler(context_PostRequestHandlerExecute); } void context_PreRequestHandlerExecute(object sender, EventArgs e) { HttpApplication context = sender as HttpApplication; IHttpHandler httpHandler = context.Context.CurrentHandler; ISingleLogin sl = httpHandler as ISingleLogin; if (sl != null) { string suid = sl.SigleUserLoginId; if (suid != string.Empty) { if (PreLogoutSessionIdDictionary.ContainsKey(context.Session.SessionID)) { //这个用户应该强制登出 PreLogoutSessionIdDictionary.Remove(context.Session.SessionID); Page page = (Page)httpHandler; page.PreInit += new EventHandler(page_PreInit); } else if (!LoginedUserIdDictionary.ContainsKey(suid)) { LoginedUserIdDictionary.Add(suid, new LifeValue(context.Session.SessionID)); } } } } void page_PreInit(object sender, EventArgs e) { Page page = sender as Page; ISingleLogin sl = page as ISingleLogin; if (sl != null) { sl.SigleUserLogout(); page.Response.End(); } } void context_PostRequestHandlerExecute(object sender, EventArgs e) { //从LogineduserId 里找到和当前用户一样的用户ID的SessionId HttpApplication context = sender as HttpApplication; IHttpHandler httpHandler = context.Context.CurrentHandler; ISingleLogin sl = httpHandler as ISingleLogin; if (sl != null) { string suid = sl.SigleUserLoginId; if (suid != string.Empty) { if (LoginedUserIdDictionary.ContainsKey(suid)) { string sessionId = LoginedUserIdDictionary[suid].value; if (sessionId != context.Session.SessionID) { if (!PreLogoutSessionIdDictionary.ContainsKey(sessionId)) { PreLogoutSessionIdDictionary.Add(sessionId, new LifeValue(suid)); } LoginedUserIdDictionary.Remove(suid); } } else { LoginedUserIdDictionary.Add(sl.SigleUserLoginId, new LifeValue(context.Session.SessionID)); } } } } #endregion } public class LifeValue { public string value; public DateTime life; public LifeValue(string value) { this.value = value; this.life = DateTime.Now.AddMinutes(HttpContext.Current.Session.Timeout + 5); } } public class StringLifeValueDictionary : Dictionary<string, LifeValue> { } public interface ISingleLogin { string SigleUserLoginId { get; } void SigleUserLogout(); }}
如此，只在在你自己的BasePage中改动相关的代码（只两三行）就可以实现功能了。
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