Global.asax

<%@ Application Language="C#" %>

<script runat="server">

    void Application_Start(object sender, EventArgs e) 
    {
        Application["OnlineUsers"] = 0;  
    }
    
    void Application_End(object sender, EventArgs e) 
    {
        //  Code that runs on application shutdown

        Session.RemoveAll();

        GlobalVariable.PermissionList = null;
        GlobalVariable.ModulePermission = null;
       
    }
        
    void Application_Error(object sender, EventArgs e) 
    { 
        // Code that runs when an unhandled error occurs

    }

    void Session_Start(object sender, EventArgs e) 
    {
        Application.Lock();
        Application["OnlineUsers"] = (int)Application["OnlineUsers"] + 1;
        Application.UnLock();  
    }

    void Session_End(object sender, EventArgs e) 
    {
        Application.Lock();
        Application["OnlineUsers"] = (int)Application["OnlineUsers"] - 1;
        Application.UnLock();

        Session.RemoveAll();
        
        GlobalVariable.PermissionList = null;
        GlobalVariable.ModulePermission = null;
    }
       
</script>