HtmlHelper building a dropdownlist, using ServiceLocator : code smell? - asp.net-mvc

Question

Is it a code smell to have to following pattern, given the following code (highly simplified to get straight to the point) ?
The models :
class Product
{
public int Id { get; set; }
public string Name { get; set; }
public Category Cat { get; set; }
}
class Category
{
public int Id { get; set; }
public string Label { get; set; }
}
The view to edit a Product :
<% =Html.EditorFor( x => x.Name ) %>
<% =Html.EditorFor( x => x.Category ) %>
The EditorTemplate for Category
<% =Html.DropDownList<Category>() %>
The HtmlHelper method
public static MvcHtmlString DropDownList<TEntity>(this HtmlHelper helper)
where TEntity : Entity
{
var selectList = new SelectList(
ServiceLocator.GetInstance<SomethingGivingMe<TEntity>>().GetAll(),
"Id", "Label");
return SelectExtensions.DropDownList(helper, "List", selectList, null, null);
}
For information, the real implementation of the helper method takes some lambdas to get the DataTextField and DataValueField names, the selected value, etc.
The point that bothers me is using a servicelocator inside the HtmlHelper. I think I should have a AllCategories property in my Product model, but I would need to be populated in the controller every time I need it.
So I think the solution I'm using is more straightforward, as the helper method is generic (and so is the modelbinder, not included here). So I just have to create an EditorTemplate for each type that needs a DropDownList.
Any advice ?

Answer 1

IMHO I'd leave it the way it is, have the same thing in another project.
BUT the service location bothered me as well so for another project I made this part of an ActionFilter which scans a model, finds all the anticipated dropdowns and does a batch load into ViewData. Since the ServiceLocator or Repository/Context/whatever is already injected into the Controller you don't have to spread your service location all over the place.
public override void OnActionExecuted(ActionExecutedContext filterContext)
{
foreach( var anticipated in SomeDetectionMethod() )
{
var selectList = new SelectList(
ServiceLocator.GetInstance<SomethingGivingMe<TEntity>>().GetAll(),
"Id", "Label");
ViewData["SelectList." + anticipated.Label/Name/Description"] = selectList;
}
}
In the view you can then make a helper to load up those dropdowns via a custom editor template or other method.

Answer 2

advice: look at the asp.net mvc sample application from here: http://valueinjecter.codeplex.com/
good luck ;)
This is how ValueInjecter's Sample Application could get the dropdowns:
(but it doesn't right now cuz I'm ok with the Resolve thing)
public class CountryToLookup : LoopValueInjection<Country, object>
{
ICountryRepo _repo;
public CountryToLookup(ICountryRepository repo)
{
_repo = repo;
}
protected override object SetValue(Country sourcePropertyValue)
{
var value = sourcePropertyValue ?? new Country();
var countries = _repo.GetAll().ToArray();
return
countries.Select(
o => new SelectListItem
{
Text = o.Name,
Value = o.Id.ToString(),
Selected = value.Id == o.Id
});
}
}