同一账户同时只能在一处登陆(单点登陆)

思路：

1：用户登陆-》产生一个随机key（guid）（服务器维护一个字典[id,key]，放在memcache中)-》同时输出key到客户端cookie

每次用户访问页面，检测是否登陆时，读取浏览器的cookie， 都判断key是否和服务器的相同。

 

eg: 用户在a在chrome登陆后，服务端产生一个guid，浏览器cookie存一份（key），服务端memcache也存一份（key + usercode, guid），

当用户a在firefox登陆后，服务端又产生了一个guid，浏览器cookie存一份（key），服务端memcache也存一份（key + usercode, guid），

当a用户再次刷新chrome时，浏览器的cookie和服务端的memcache的value（通过usercode查memcache的value）不一样了，强制退出。

 

 1 /// <summary>
 2         /// memcache,这里自己去定义
 3         /// </summary>
 4         private static cacheserver _cacheserver = cacheserver.getcacheoperateinstance();
 5 
 6         /// <summary>
 7         /// 设置cookie
 8         /// </summary>
 9         /// <param name="cookiename"></param>
10         /// <param name="cookievalue"></param>
11         /// <param name="expires"></param>
12         public static void setcookie(string cookiename, string cookievalue, datetime expires)
13         {
14             httpcookie cookie = new httpcookie(cookiename)
15             {
16                 value = cookievalue,
17                 expires = expires
18             };
19             system.web.httpcontext.current.response.cookies.add(cookie);
20         }
21 
22         /// <summary>
23         /// 登陆成功后执行
24         /// </summary>
25         /// <param name="islogin"></param>
26         /// <param name="pusercode"></param>
27         /// <param name="cookiedomain"></param>
28         public void singlelogin(bool islogin, string pusercode, string cookiedomain)
29         {
30             if (islogin)
31             {
32                 #region 限制同一账户同时只能在一处登陆 
33                 string singlekey = "singleguid";
34                 string singlevalue = guid.newguid().tostring();
35                 setcookie(singlekey, cookiedomain, datetime.now.adddays(7));
36                 _cacheserver.addcacheruntime(singlekey + pusercode.tolower(), singlevalue, 1440 * 3);
37                 #endregion
38             }
39         }

basecontrol中的代码：

 1 /// <summary>  
 2         /// 获取指定cookie值  
 3         /// </summary>  
 4         /// <param name="cookiename">cookiename</param>  
 5         /// <returns></returns>  
 6         public static string getcookievalue(string cookiename)
 7         {
 8             httpcookie cookie = system.web.httpcontext.current.request.cookies[cookiename];
 9             string str = string.empty;
10             if (cookie != null)
11             {
12                 str = cookie.value;
13             }
14             return str;
15         }
16 
17         /// <summary>
18         /// 名称：清除cookie
19         /// </summary>
20         private void removeallcookiesbase()
21         {
22             foreach (string key in httpcontext.request.cookies.allkeys)
23             {
24                 httpcookie cookie = httpcontext.request.cookies[key];
25                 cookie.domain = system.configuration.configurationmanager.appsettings["cookiedomain"];
26                 cookie.expires = datetime.now.adddays(-1);
27                 httpcontext.response.cookies.add(cookie);
28             }
29             
30         }
31         
32         /// <summary>
33         /// basecontrol中onactionexecuting中的代码
34         /// </summary>
35         /// <param name="filtercontext"></param>
36         protected override void onactionexecuting(actionexecutingcontext filtercontext)
37         {
38             //你的登陆对象，自己修改
39             usermodel _userprofile = new usermodel();
40 
41             #region 限制同一账户同时只能在一处登陆
42             string singlekey = "singleguid";
43             //从客户端cookie取值
44             var clientvalue = getcookievalue(singlekey);
45 
46             string servervalue = string.empty;
47             //从服务端cache获取
48             var servervalueobj = _cacheserver.getvaluewithcache(singlekey + _userprofile.usercode.tolower());
49             if (servervalueobj != null)
50             {
51                 servervalue = convert.tostring(servervalueobj);
52             }
53 
54             if (!servervalue.equals(clientvalue))
55             {
56                 removeallcookiesbase();
57                 system.web.security.formsauthentication.signout();
58 
59                 //登陆系统地址
60                 string loginurl = system.configuration.configurationmanager.appsettings["loginpath"];
61                 string hosturl = filtercontext.httpcontext.request.url.host;
62                 var https_hosturl = "http://" + hosturl + "/";
63                 filtercontext.result = new redirectresult(loginurl + https_hosturl);
64             }
　　　　        base.onactionexecuting(filtercontext);
65             #endregion
66         }

根据自己项目的实际情况，适当的修改代码。