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
ExpandedBlockStart.gifContractedBlock.gif {
ExpandedSubBlockStart.gifContractedSubBlock.gif string SigleUserLoginId { get; }

void SigleUserLogout();

}

public class BasePage : System.Web.UI.Page , BNet.Web.Modulers.ISingleLogin
ExpandedBlockStart.gifContractedBlock.gif {
public BasePage()
ExpandedSubBlockStart.gifContractedSubBlock.gif {
//
// TODO: 在此处添加构造函数逻辑
//
}

protected override void OnLoad(EventArgs e)
ExpandedSubBlockStart.gifContractedSubBlock.gif {
base.OnLoad(e);
if (Session["UserId"] == null)
ExpandedSubBlockStart.gifContractedSubBlock.gif {
Response.Write("你还没有登陆");
Response.Redirect("login.aspx");
}
}

ContractedSubBlock.gifExpandedSubBlockStart.gif ISingleLogin 成员#region ISingleLogin 成员

public string SigleUserLoginId
ExpandedSubBlockStart.gifContractedSubBlock.gif {
get
ExpandedSubBlockStart.gifContractedSubBlock.gif {
if (Session["UserId"] != null)
ExpandedSubBlockStart.gifContractedSubBlock.gif {
return Session["UserId"].ToString();
}
else
return "";
}
}

public void SigleUserLogout()
ExpandedSubBlockStart.gifContractedSubBlock.gif {
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:

< system .web >
< httpModules >
< add name ="SingleLogin" type ="BNet.Web.Modulers.SingleLoginModuler" />

</ httpModules >
</ system.web >

相关的SigleLoginModuler代码如下:[依评论修改后]

using System;
using System.Collections.Generic;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.UI;

namespace BNet.Web.Modulers
ExpandedBlockStart.gifContractedBlock.gif {
ExpandedSubBlockStart.gifContractedSubBlock.gif /**//// <summary>
/// SingleLoginModuler 的摘要说明
/// </summary>
public class SingleLoginModuler : System.Web.IHttpModule
ExpandedSubBlockStart.gifContractedSubBlock.gif {
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)
ExpandedSubBlockStart.gifContractedSubBlock.gif {
if (dic == null)
ExpandedSubBlockStart.gifContractedSubBlock.gif {
dic = new StringLifeValueDictionary();
}
else
ExpandedSubBlockStart.gifContractedSubBlock.gif {
List<string> listRemove = new List<string>();
StringLifeValueDictionary.Enumerator iter = dic.GetEnumerator();
while (iter.MoveNext())
ExpandedSubBlockStart.gifContractedSubBlock.gif {
if (iter.Current.Value.life < DateTime.Now)
ExpandedSubBlockStart.gifContractedSubBlock.gif {
listRemove.Add(iter.Current.Key);
}
}

foreach (string key in listRemove)
ExpandedSubBlockStart.gifContractedSubBlock.gif {
dic.Remove(key);
}
}

return dic;
}

static StringLifeValueDictionary loginedUserIdDictionary = null;
static StringLifeValueDictionary LoginedUserIdDictionary
ExpandedSubBlockStart.gifContractedSubBlock.gif {
get
ExpandedSubBlockStart.gifContractedSubBlock.gif {
return UsableGetter(ref loginedUserIdDictionary);
}
}

static StringLifeValueDictionary preLogoutSessionIdDictionary = null;
static StringLifeValueDictionary PreLogoutSessionIdDictionary
ExpandedSubBlockStart.gifContractedSubBlock.gif {
get
ExpandedSubBlockStart.gifContractedSubBlock.gif {
return UsableGetter(ref preLogoutSessionIdDictionary);
}
}

public SingleLoginModuler()
ExpandedSubBlockStart.gifContractedSubBlock.gif {
//
// TODO: 在此处添加构造函数逻辑
//
}

ContractedSubBlock.gifExpandedSubBlockStart.gif IHttpModule 成员#region IHttpModule 成员

public void Dispose()
ExpandedSubBlockStart.gifContractedSubBlock.gif {
}

public void Init(HttpApplication context)
ExpandedSubBlockStart.gifContractedSubBlock.gif {
context.PreRequestHandlerExecute += new EventHandler(context_PreRequestHandlerExecute);
context.PostRequestHandlerExecute += new EventHandler(context_PostRequestHandlerExecute);

}



void context_PreRequestHandlerExecute(object sender, EventArgs e)
ExpandedSubBlockStart.gifContractedSubBlock.gif {
HttpApplication context = sender as HttpApplication;
IHttpHandler httpHandler = context.Context.CurrentHandler;
ISingleLogin sl = httpHandler as ISingleLogin;
if (sl != null)
ExpandedSubBlockStart.gifContractedSubBlock.gif {
string suid = sl.SigleUserLoginId;
if (suid != string.Empty)
ExpandedSubBlockStart.gifContractedSubBlock.gif {
if (PreLogoutSessionIdDictionary.ContainsKey(context.Session.SessionID))
ExpandedSubBlockStart.gifContractedSubBlock.gif {
//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))
ExpandedSubBlockStart.gifContractedSubBlock.gif {
LoginedUserIdDictionary.Add(suid, new LifeValue(context.Session.SessionID));
}
}
}

}

void page_PreInit(object sender, EventArgs e)
ExpandedSubBlockStart.gifContractedSubBlock.gif {
Page page = sender as Page;
ISingleLogin sl = page as ISingleLogin;
if (sl != null)
ExpandedSubBlockStart.gifContractedSubBlock.gif {
sl.SigleUserLogout();
page.Response.End();
}
}

void context_PostRequestHandlerExecute(object sender, EventArgs e)
ExpandedSubBlockStart.gifContractedSubBlock.gif {
//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)
ExpandedSubBlockStart.gifContractedSubBlock.gif {
string suid = sl.SigleUserLoginId;
if (suid != string.Empty)
ExpandedSubBlockStart.gifContractedSubBlock.gif {
if (LoginedUserIdDictionary.ContainsKey(suid))
ExpandedSubBlockStart.gifContractedSubBlock.gif