MVC: Binding dynamic select list back to ViewModel on Post - asp.net-mvc

Question

I have a MVC 3 project, and is stuck on the binding of the view back to the model on Post.
Here is my Model:
public class DBViewModel
{
public ProductionDatabasesViewModel PDBViewModel { get; set; }
public IList<string> SelectedNames { get; set; }
public DBViewModel()
{
SelectedNames = new List<string>();
PDBViewModel = new ProductionDatabasesViewModel();
}
}
My view: (cut down version)
#model Web.Models.DBViewModel
#using (Html.BeginForm())
{
#Html.ValidationSummary(true)
<fieldset>
#Html.ListBoxFor(x => x.SelectedNames, new SelectList(Model.SelectedNames))
<input id="button-submit" name="SubmitButton" type="submit" value="Submit" />
</fieldset>
}
Snippet of the Controller:
[HttpPost]
public ActionResult Database(DBViewModel model)
{
var users = model.SelectedNames; //<---- empty, the count is 0 always.
}
In the view there is the ability to select users from a autocomplete box and then jQuery script that will add the selected names to the list in the view above. This all works, so I can search for the users, and then click the add button to add the users to the list. But I run into problems when clicking the Submit button. The users that were added in the view (selectlist in the view), is not bound to the Model. So on post the model.SelectedNames is empty. I have also tried Request["SelectedNames"] and Request.Form["SelectedNames"] and they are all null.
I am very experienced in normal webforms, but still learning MVC, so any help would be much appreciated.
[UPDATE]
I will update the question further tomorrow my time, but it appears that the items that is in the list will be bound to the viewmodel if I select them. I will figure this out tomorrow. But thanks a lot so far for all the comments, help and suggestions.

Answer 1

Does this Does the Model Binder in ASP.NET MVC Beta Support List<T>? answer your question? The string list is a simpler version.

Answer 2

Have to say this cut off version of your code works as it should. SelectedNames list is successfully filled from listbox after submit. You can check it yourself. Though I have made several changes:
removed all references to ProductionDatabasesViewModel;
changed return type of POST version of Database method to void;
added GET version of Database method
:
public ActionResult Database()
{
return View(new DBViewModel { SelectedNames = { "a", "b", "c" } });
}
So I believe you have a bug somethere else, not in these parts.

Answer 3

Ok, I have found what the issue is. When you have a multi select element in your html that you want to bind the values in the box back to the model, you have to select the items first. Very annoying, but that's the way it seems to want it.
So if you have a select box like:
<select id="selected-ad-users-list" name="SelectedNames" multiple="multiple" size="5"
style="width: 100%">
</select>
And you add items to it, from anywhere really, in my case I had another list/or textbox where they typed a name in, and then I used jQuery to populate this select list. What I needed to do was to add a bit of jQuery script to spin through my list and select all items. So once the items are selected, it will bind them to the model.
Here is a good article on this: select all or some items in a select box
I really hope this helps someone.