Binding contained collections from Edit Action #model view? - asp.net-mvc

Question

Can somebody please provide code to allow [] to be used so as to save contained collection within a #model?
Edit View:
#model MVC3.Models.A
// I need to save collection values but can't use [] here to setup model binding.
#Html.EditorFor(model => model.Bs[0].Val)
Models:
public class A
{
public A()
{
this.Bs = new HashSet<B>();
}
public int Name { get; set; }
public virtual ICollection<B> Bs { get; set; }
}
public class B
{
public int Val { get; set; }
public virtual A A { get; set; }
}

Answer 1

The problem is that your property is an ICollection<T>, which doesn't provide indexed access to elements.
Change it to an IList<T> or just a List<T> and you can write your view code as it is in your first example.
If you can't change the property type for some reason, then you'll need to create a specialized view model for your particular view and then map it to the A model in the controller POST action.
Alternatively, it is possible (albeit a little awkward) to bind to simple collection types directly as long as you follow the proper HTML conventions, which means using multiple input elements with the same name, as described by Phil Haack, i.e.:
<input type="text" name="ints" value="1" />
<input type="text" name="ints" value="4" />
<input type="text" name="ints" value="2" />
<input type="text" name="ints" value="8" />
But this only works for simple types, i.e. primitives or strings, not complex types like whatever B is in this context.
One final comment: If you're using editor templates, you can usually just bind to the entire collection and the MVC framework will figure out how to put it back together, as in just:
#Html.EditorFor(m => m.Bs);
Of course this gives you no control over what goes between the editor templates for each item, so if you're trying to generate <li> elements for them or something like that, then you'll have to embed it directly into the editor template which possibly means creating a custom editor template specifically for this collection binding and using the corresponding override of EditorFor (the one that takes a template name).
It's a bit of a pain, but could be less work than trying to switch to a parallel-model system, if you've been sharing classes between your UI and data layers up 'til now.