[转]利用HttpModuler实现WEB程序同一时间只让一个用户实例登陆

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
}

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

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

namespace BNet.Web.Modulers
{
//// <summary>
/// SingleLoginModuler 的摘要说明
/// </summary>
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();

}
}