How to set Default Controller in asp.net MVC 4 & MVC 5

the best way is to change your route. The default route (defined in your App_Start) sets /Home/Index

routes.MapRoute(
        "Default", // Route name
        "{controller}/{action}/{id}", // URL with parameters*
        new { controller = "Home", action = "Index", 
        id = UrlParameter.Optional }
);

as the default landing page. You can change that to be any route you wish.

routes.MapRoute(
        "Default", // Route name
        "{controller}/{action}/{id}", // URL with parameters*
        new { controller = "Sales", action = "ProjectionReport", 
        id = UrlParameter.Optional }
);

Set below code in RouteConfig.cs in App_Start folder

public static void RegisterRoutes(RouteCollection routes)
{
 routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
 routes.MapRoute(
 name: "Default",
 url: "{controller}/{action}/{id}",
 defaults: new { controller = "Account", action = "Login", id = UrlParameter.Optional });
}

IF still not working then do below steps

Second Way : You simple follow below steps,

1) Right click on your Project

2) Select Properties

3) Select Web option and then Select Specific Page (Controller/View) and then set your login page

Here, Account is my controller and Login is my action method (saved in Account Controller)

Please take a look attached screenshot.