Passing a {sitename} parameter to MVC controller actions - asp.net-mvc

Question

How can I retrieve a site-wide URL parameter in a route without cluttering each controller action with a parameter? My question is similar to this question, but I want to avoid the ModelBinder clutter. Ie. in Global.asax.cs:
routes.MapRoute(
"Default", // Route name
"{sitename}/{controller}/{action}/{id}",
new { sitename = "", controller = "SomeController", action = "Index", id = "" } );
So, instead of the following in SomeController class:
public ActionResult Index(string sitename)
{
SiteClass site = GetSite(sitename);
...
return View(site.GetViewModel());
}
I would rather have the following:
public ActionResult Index()
{
SiteClass site = CurrentSite; // where CurrentSite has already retrieved data based on unique URL sitename parameter.
...
return View(site.GetViewModel());
}
Perhaps this can be achieved with controller-wide action filter? OnActionExecuting?

Answer 1

First add a route to Global.aspx.cs to pass a {sitename} parameter:
routes.MapRoute(
"Sites", // Route name
"{sitename}/{controller}/{action}/{id}", // URL with parameters
new { sitename = "", controller = "Home", action = "Index", id = "" } // Parameter defaults
);
Then add the following simple code inside a base controller:
public class BaseController: Controller
{
public string SiteName = "";
protected override void OnActionExecuting(ActionExecutingContext filterContext)
{
HttpRequestBase req = filterContext.HttpContext.Request;
SiteName = filterContext.RouteData.Values["sitename"] as string;
base.OnActionExecuting(filterContext);
}
}
And use in your derived controller:
public class HomeController: BaseController
{
public ActionResult Index()
{
ViewData["SiteName"] = SiteName;
return View();
}
}

Answer 2

Perhaps I misunderstand the question, but why not simply do the following inside your controller action:
var sitename = RouteData.Values["sitename"] as string;
I don't understand why you would need to override OnActionExecuting (per #pate's answer) when you can retrieve the value when you need it.
There's also no need to create a base class and have everything derive from it. If you object to copying that line into every action method of every controller, why not create an extension method?