C#

Application.Run(new Form1());

Application.EnableVisualStyles();

void Application_Start(object sender, EventArgs e) 
    {
        // Code that runs on application startup
        Application.Add(numOfUsers, 0);

    }
    
    void Application_End(object sender, EventArgs e) 
    {
        //  Code that runs on application shutdown
        
    }

    void Session_Start(object sender, EventArgs e) 
    {
        // Code that runs when a new session is started
        int n = Convert.ToInt32(Application["numOfUsers"]);
        n++;
        Application["numOfUsers"] = n;
    }

    void Session_End(object sender, EventArgs e) 
    {
        // Code that runs when a session ends. 
        // Note: The Session_End event is raised only when the sessionstate  mode
        // is set to InProc in the Web.config file. If session mode is set to StateServer 
        // or SQLServer, the event is not raised.
        int n = Convert.ToInt32(Application["numOfUsers"]);
        n--;
        Application["numOfUsers"] = n;

    } 

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"The Soapbox has been so ..."

protected internal static readonly ... and I wish the list could continue ...

Google talk: binarybandit