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：
publicinterfaceISingleLogin\r\n{\r\n stringSigleUserLoginId{get;}\r\n voidSigleUserLogout();\r\n}\r\npublicclassBasePage:System.Web.UI.Page,BNet.Web.Modulers.ISingleLogin\r\n{\r\n publicBasePage()\r\n {\r\n //\r\n //TODO:在此处添加构造函数逻辑\r\n //\r\n }\r\n protectedoverridevoidOnLoad(EventArgse)\r\n {\r\n base.OnLoad(e);\r\n if(Session[UserId]==null)\r\n {\r\n Response.Write(你还没有登陆);\r\n Response.Redirect(login.aspx);\r\n }\r\n }\r\n ISingleLogin成员#regionISingleLogin成员\r\n publicstringSigleUserLoginId\r\n {\r\n get\r\n {\r\n if(Session[UserId]!=null)\r\n {\r\n returnSession[UserId].ToString();\r\n }\r\n else\r\n return;\r\n }\r\n }\r\n publicvoidSigleUserLogout()\r\n {\r\n Session.Abandon();\r\n Response.Write(你在别处已经登陆，强制退出本次登陆!);\r\n }\r\n}\r\n然后在Web.config中加入HttpModuler：\r\nsystem.web\r\nhttpModules\r\naddname=SingleLogintype=BNet.Web.Modulers.SingleLoginModuler/\r\n/httpModules\r\n/system.web\r\n相关的SigleLoginModuler代码如下：[依评论修改后]\r\nusingSystem;\r\nusingSystem.Collections.Generic;\r\nusingSystem.Data;\r\nusingSystem.Configuration;\r\nusingSystem.Web;\r\nusingSystem.Web.UI;\r\nnamespaceBNet.Web.Modulers\r\n{\r\n /**////summary\r\n ///SingleLoginModuler的摘要说明\r\n ////summary\r\n publicclassSingleLoginModuler:System.Web.IHttpModule\r\n {\r\n conststringsigle_login_userid=evlon_siglelogin_userid;\r\n conststringsigle_pre_logout_sessionid=evlon_sigle_pre_logout_sessionid;\r\n publicstaticStringLifeValueDictionaryUsableGetter(refStringLifeValueDictionarydic)\r\n {\r\n if(dic==null)\r\n {\r\n dic=newStringLifeValueDictionary();\r\n }\r\n else\r\n {\r\n ListstringlistRemove=newListstring();\r\n StringLifeValueDictionary.Enumeratoriter=dic.GetEnumerator();\r\n while(iter.MoveNext())\r\n {\r\n if(iter.Current.Value.lifeDateTime.Now)\r\n {\r\n listRemove.Add(iter.Current.Key);\r\n }\r\n }\r\n foreach(stringkeyinlistRemove)\r\n {\r\n dic.Remove(key);\r\n }\r\n }\r\n returndic;\r\n }\r\n staticStringLifeValueDictionaryloginedUserIdDictionary=null;\r\n staticStringLifeValueDictionaryLoginedUserIdDictionary\r\n {\r\n get\r\n {\r\n returnUsableGetter(refloginedUserIdDictionary);\r\n }\r\n }\r\n staticStringLifeValueDictionarypreLogoutSessionIdDictionary=null;\r\n staticStringLifeValueDictionaryPreLogoutSessionIdDictionary\r\n {\r\n get\r\n {\r\n returnUsableGetter(refpreLogoutSessionIdDictionary);\r\n }\r\n }\r\n publicSingleLoginModuler()\r\n {\r\n //\r\n //TODO:在此处添加构造函数逻辑\r\n //\r\n }\r\n IHttpModule成员#regionIHttpModule成员\r\n publicvoidDispose()\r\n {\r\n }\r\n publicvoidInit(HttpApplicationcontext)\r\n {\r\n context.PreRequestHandlerExecute+=newEventHandler(context_PreRequestHandlerExecute);\r\n context.PostRequestHandlerExecute+=newEventHandler(context_PostRequestHandlerExecute);\r\n }\r\n voidcontext_PreRequestHandlerExecute(objectsender,EventArgse)\r\n {\r\n HttpApplicationcontext=senderasHttpApplication;\r\n IHttpHandlerhttpHandler=context.Context.CurrentHandler;\r\n ISingleLoginsl=httpHandlerasISingleLogin;\r\n if(sl!=null)\r\n {\r\n stringsuid=sl.SigleUserLoginId;\r\n if(suid!=string.Empty)\r\n {\r\n if(PreLogoutSessionIdDictionary.ContainsKey(context.Session.SessionID))\r\n {\r\n //这个用户应该强制登出\r\n PreLogoutSessionIdDictionary.Remove(context.Session.SessionID);\r\n Pagepage=(Page)httpHandler;\r\n page.PreInit+=newEventHandler(page_PreInit);\r\n }\r\n elseif(!LoginedUserIdDictionary.ContainsKey(suid))\r\n {\r\n LoginedUserIdDictionary.Add(suid,newLifeValue(context.Session.SessionID));\r\n }\r\n }\r\n }\r\n }\r\n voidpage_PreInit(objectsender,EventArgse)\r\n {\r\n Pagepage=senderasPage;\r\n ISingleLoginsl=pageasISingleLogin;\r\n if(sl!=null)\r\n {\r\n sl.SigleUserLogout();\r\n page.Response.End();\r\n }\r\n }\r\n voidcontext_PostRequestHandlerExecute(objectsender,EventArgse)\r\n {\r\n //从LogineduserId里找到和当前用户一样的用户ID的SessionId\r\n HttpApplicationcontext=senderasHttpApplication;\r\n IHttpHandlerhttpHandler=context.Context.CurrentHandler;\r\n ISingleLoginsl=httpHandlerasISingleLogin;\r\n if(sl!=null)\r\n {\r\n stringsuid=sl.SigleUserLoginId;\r\n if(suid!=string.Empty)\r\n {\r\n if(LoginedUserIdDictionary.ContainsKey(suid))\r\n {\r\n stringsessionId=LoginedUserIdDictionary[suid].value;\r\n if(sessionId!=context.Session.SessionID)\r\n {\r\n if(!PreLogoutSessionIdDictionary.ContainsKey(sessionId))\r\n {\r\n PreLogoutSessionIdDictionary.Add(sessionId,newLifeValue(suid));\r\n }\r\n LoginedUserIdDictionary.Remove(suid);\r\n }\r\n }\r\n else\r\n {\r\n LoginedUserIdDictionary.Add(sl.SigleUserLoginId,newLifeValue(context.Session.SessionID));\r\n }\r\n }\r\n }\r\n }\r\n #endregion\r\n }\r\n publicclassLifeValue\r\n {\r\n publicstringvalue;\r\n publicDateTimelife;\r\n publicLifeValue(stringvalue)\r\n {\r\n this.value=value;\r\n this.life=DateTime.Now.AddMinutes(HttpContext.Current.Session.Timeout+5);\r\n }\r\n }\r\n publicclassStringLifeValueDictionary:Dictionarystring,LifeValue\r\n {\r\n }\r\n publicinterfaceISingleLogin\r\n {\r\n stringSigleUserLoginId{get;}\r\n voidSigleUserLogout();\r\n }\r\n}
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。