How to manage models that are being displayed in a shared layout? - asp.net-mvc

Question

I'm working on a new MVC/Razor website, and we've gotten to the point where we need to put in a real menu structure. Currently, our menus are hardcoded into the global shared layout, we need to populate the menus from code, so that we can determine, after login, which menus will be displayed for a user.
We'll want the menus to appear on pretty much every page, except for login and a few other special cases. So we'll continue to one them to be rendered in the shared layout.
It looks simple enough to create an #Html.DisplayFor template that would render a menu item. The question is, how to get data to it?
The shared layout is used with quite a number of views, handling a number of different models, being loaded from a number of controllers.
Adding a List member to each model, and then populating it in each controller, seems tedious, bothersome, and error prone.
Or we could skip adding the collection to each model, and instead have each controller stick it in the ViewBag. That doesn't seem all that great, either.
The only possibility I've been able to dream up, to keep from having to repeat this for every controller, is to define a common base class, derived from Controller, that all of the controllers that use the shared layout could derive from, in turn, that would stuff the MenuItem collection into the ViewBag.
But I'm wondering if I'm missing something. Is there some preferred way of dealing with this situation?

Answer 1

Shared/base view models is a way to go as you mentioned, but in my opinion its not very "single responsibility". Having to inherit from a base model and add menu items on each page is tedious as you mentioned.
If I was you I would use:
#Html.Action("action", "controller")
https://msdn.microsoft.com/en-us/library/ee703457.aspx
This would call an action method, and then you can bind a specific menu model and also return a specific partial view that would be rendered in the view that called it
#Html.Action("TopMenu", "Controller")
[ChildActionOnly]
public PartialViewResult TopMenu()
{
return PartialView(new MenuModel());
}
Create a TopMenu.cshtml
You can even go as far as passing in values into the controller action to modify the output model/view.
You can call #Html.Action from your layout/shared view.
EDIT
Added [ChildActionOnly] as highlighted in comment as this prevents access to the action unless it was called from a parent action and should be used here

Answer 2

If I understand your question correctly...
I prefer to have a MasterViewModel that every ViewModel for every page inherits from. The MasterViewModel holds things common to every page, like the user's name, navigation rules, etc. The shared layout then uses #model MasterViewModel, which is populated by an ActionFilterAttribute.
public class MasterViewModel
{
public IEnumerable<string> NavItems {get; set;}
}
public class HomeIndexViewModel : MasterViewModel
{
// stuff for the home view
}
I then have a MasterViewModelAttribute:
public class MasterViewModelAttribute : ActionFilterAttribute
{
[Inject]
public IDatabase Database { get; set; }
public override void OnActionExecuted(ActionExecutedContext filterContext)
{
base.OnActionExecuted(filterContext);
ViewResultBase viewResult = filterContext.Result as ViewResultBase;
// not a view result
if (viewResult == null)
{
return;
}
MasterViewModel model = viewResult.ViewData.Model as MasterViewModel;
// not a MasterViewModel view model
if (model == null)
{
return;
}
model.NavItems = // set your nav items
}
}
Then, every controller derives from a base controller, which implements the attribute:
[MasterViewModel]
public class BaseController : Controller
{
}
And for each controller:
public class HomeController : BaseController
{
public ActionResult Index()
{
return View(new HomeIndexViewModel());
}
}
And finally, the layout:
#model MasterViewModel
// omitted
<div class="nav">
#foreach (var item in Model.NavItems)
{
<a></a>
}
</div>
The thing I like about the pattern is that you still get strong type-checking by using ViewModels (as opposed to the ViewBag), and you don't have to deal with all the extra nav stuff when you want to unit test an action, for example.
This also has an advantage over using partial views and #Html.Action() in that you don't incur a second request to the server for every page load.