How to Check session value before the action gets executed

Step:1
 First of all create a class named pageFilter in your solution and write following code.

public class PageFilter : ActionFilterAttribute

   {

       public override void OnActionExecuting(ActionExecutingContext filterContext)

       {

           HttpContext ctx = HttpContext.Current;

               // If the browser session has expired...

               if (ctx.Session["UserName"] == null)

               {

                   if (filterContext.HttpContext.Request.IsAjaxRequest())

                   {

                       filterContext.Result = new JsonResult { Data = "_Logon_" };

                   }

                   else

                   {

                       filterContext.Result = new RedirectToRouteResult(

                           new RouteValueDictionary {

                               { "Controller", "Demo" },

                               { "Action", "Login" }

                       });

                   }

               }

       }

}

Step-2

Then add [PageFilter] attribute to your controller class .

Example:-

[PageFilter]

public class DemoController : Controller

{

}