Redirect user to login page if session null in MVC 5 Razor syntax

For Example using MVC 5 Razor:

 @{

     //get user session.

     var session = UserManager.Session();

     if (session == null)

     {

        Response.Redirect("~/Account/LogOff");

     }

 }

                                          OR

We can also use the custom action filter to achieve this functionality. i.e.

For Example :

// Override onAuthentication filter to achieve this functionality.

//and also get user session to check is null value.

protected override void OnAuthentication(AuthenticationContext filterContext)

{

      session = UserManager.Session();

      if ( session == null)

      {

        RedirectToControllers(Helper.Control.ACCOUNT, Helper.Action.ACCOUNT_LOGIN);

      }

      base.OnAuthentication(filterContext);

}