asp.net's next account does not allow multiple users to be online at the same time

Method 1:

 
string sKey = username.Text.ToString().Trim(); //  get Cache In a given Key The value of the  
string sUser = Convert.ToString(Cache[sKey]); //  Check for presence  
if (sUser == null || sUser == String.Empty) 
{ 
TimeSpan SessTimeOut = new TimeSpan(0, 0, System.Web.HttpContext.Current.Session.Timeout, 0, 0);// achieve Session Expiration time  
HttpContext.Current.Cache.Insert(sKey, sKey, null, DateTime.MaxValue, SessTimeOut, System.Web.Caching.CacheItemPriority.NotRemovable, null);// The value in the cache Convenient for single sign-on  
// A successful login  
} 
else if (Cache[sKey].ToString() == sKey)// If the account is already logged in  
{ 
ClientScript.RegisterStartupScript(GetType(), " prompt ", "<script>alert(' I'm sorry , The current user is logged in ');</script>"); 
return; 
} 
else 
{ 
Session.Abandon();// The main purpose of this section is to avoid unnecessary errors that may cause you to fail to log in  
} 

 
// Clear when closing the browser or window Cache The method of . In the main page aspx Add to file 1 a onunload The event . through ajax empty hOnline In the Session.SessionID 
window.onunload=function(){ 
$.ajax({ 
type: "POST", 
　　　data:"sKey="+sKey; 
url: "online.aspx" 
}); 
} 

online. aspx. cs code

 
protected void Page_Load(object sender, EventArgs e) 
{ 
　　　　HttpContext.Current.Cache.Remove(sKey); 
} 
// in Global.asax In the file Session_End Add to the method  
//Session After expired . empty hOnline In the Session.SessionID 
　　　　Hashtable hOnline = (Hashtable)Application["Online"]; 
if (hOnline[Session.SessionID] != null) 
{ 
hOnline.Remove(Session.SessionID); 
Application.Lock(); 
Application["Online"] = hOnline; 
Application.UnLock(); 
} 

Method 2:

 
//sKey Is the login user name  
if(ApplicationOnline(username.Text.tirm())){ 
Hashtable hOnline = new Hashtable(); 
hOnline[Session.SessionID] = sKey; 
Application.Lock(); 
Application["Online"] = hOnline; 
Application.UnLock(); 
} 

public Boolean ApplicationOnline(string sKey) 
{ 
Boolean flag = true; 
Hashtable hOnline = (Hashtable)Application["Online"]; 
if (hOnline != null) 
{ 
IDictionaryEnumerator idE = hOnline.GetEnumerator(); 
while (idE.MoveNext()) 
{ 
//if (idE.Key != null && idE.Key.ToString().Equals(Session.SessionID)) 
//{ 
if (idE.Value != null && sKey.Equals(idE.Value.ToString())) 
{ 
flag = false; 
} 
break; 
//} 
} 
} 
return flag; 
} 

// Clear when closing the browser or window Session.SessionID The method of . In the main page aspx Add to file 1 a onunload The event . through ajax empty Session.SessionID 
window.onunload=function(){ 
$.ajax({ 
type: "POST", 
url: "online.aspx" 
}); 
} 

online. aspx. cs code

 
protected void Page_Load(object sender, EventArgs e) 
{ 
Hashtable hOnline = (Hashtable)Application["Online"]; 
if (hOnline[Session.SessionID] != null) 
{ 
hOnline.Remove(Session.SessionID); 
Application.Lock(); 
Application["Online"] = hOnline; 
Application.UnLock(); 
} 
}