I cant access to HttpContext.Application It always return null

Question

this is my code for counting online users it works well in global.asax and it count well but when I call it from controller it returns null

 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();
    }

    protected void Application_Start()
    {
        Application["OnlineUsers"] = 0;

    }

in controller:

string strUsersOnline = HttpContext.Application["OnlineUsers"] as string;
        ViewData["OnlineUsers"] = strUsersOnline;

Answer 1

The value is null because the of the as keyword, use explicit conversion or .ToString()

Refer MSDN