What are different ways of rendering layout in ASP.NET MVC?

There are following four different ways of rendering layout in ASP.NET MVC:

1. Using _ViewStart file in the root directory of the Views folder: The _ViewStart file with in Views folder is used to server the default Layout page for your ASP.NET MVC application. You can also change the default rendering of layouts with in _ViewStart file based on controller as shown below:

   @{
   	var controller = HttpContext.Current.Request.RequestContext.RouteData.Values["Controller"].ToString();
   	string layout = "";
   	if (controller == "Admin") {
   		layout = "~/Views/Shared/_AdminLayout.cshtml";
   	} else {
   		layout = "~/Views/Shared/_Layout.cshtml";
   	}
   	Layout = layout;
   }

2. Adding _ViewStart file in each of the directories: You can also set the default layout for a particular directory by putting _ViewStart file in each of the directories with the required Layout information as shown below:
3. Defining Layout with in each view on the top

   @{
       Layout = "~/Views/Shared/_AdminLayout.cshtml";
   }

4. Returning Layout from ActionResult

   public ActionResult Index()
   {
       RegisterModel model = new RegisterModel();
       //TO DO:
       return View("Index", "_AdminLayout", model);
   }