Can't set SelectedItem in DropDownList in my MVC3 view - asp.net-mvc-3

Question

I know that I can set the SelectedItem in my controller, but I can't figure out how to set it in my view. I'm working on a sort of flashcard (study guide) application and I have imported about 400 test questions. Now I want to write a page for the instructor to be able to select a "Category" for each question. I'd like them to be able to update the category for all the questions on one page. My model has a question entity that contains a foreign key field to the category entity (the field is called QuestionCategory). So, my view is based on the Question entity, but I'm sending over the list of Categories (there are 14) in the ViewBag (so I don't have to send a full SelectList over with each of the 400 questions. As my view is iterating thru the items in my View, I just want to add a SelectList that contains the 14 categories in my ViewBag and then set the SelectedItem based on the value of item.QuestionCategory. I can't make it work.
Here's my controller action:
public ActionResult Index()
{
var context = new HBModel.HBEntities();
var query = from q in context.tblQuestions.Include("tblCategory") select q;
var questions = query.ToList();
ViewBag.Categories = new SelectList(context.tblCategories, "CategoryID", "CategoryName");
return View(questions);
}
Here's some of the things I've tried in the view (with associated error messages in the comments)
#model IEnumerable<HBModel.tblQuestion>
#{
ViewBag.Title = "Index";
Layout = "~/Views/Shared/_Layout.cshtml";
}
<h2>Index</h2>
<p>
#Html.ActionLink("Create New", "Create")
</p>
<table>
<tr>
<th>
Question
</th>
<th>
Answer
</th>
<th>
AnswerSource
</th>
<th>
Category
</th>
<th>
Action
</th>
</tr>
#foreach (var item in Model) {
<tr>
<td>
#item.Question
</td>
<td>
#item.Answer
</td>
<td>
#item.AnswerSource
</td>
<td>
#item.tblCategory.CategoryName
#*This one works, but cannot initialize the selected item to be current database value*#
#Html.DropDownList("Categories")
#*compile error - CS0200: Property or indexer 'System.Web.Mvc.SelectList.SelectedValue' cannot be assigned to -- it is read only*#
#*#Html.DropDownListFor(m => item.QuestionCategory, (ViewBag.Categories as SelectList).SelectedValue = item.QuestionCategory)*#
#*error {"DataBinding: 'System.Web.Mvc.SelectListItem' does not contain a property with the name 'CategoryId'."}*#
#Html.DropDownListFor(m => item.QuestionCategory, new SelectList(ViewBag.Categories, "CategoryId", "CategoryName"))
#*error - {"DataBinding: 'System.Char' does not contain a property with the name 'CategoryId'."}*#
#Html.DropDownListFor(m => item.QuestionCategory, new SelectList("Categories", "CategoryId", "CategoryName"))
)
</td>
<td style="width: 100px">
#Html.ActionLink("Edit", "Edit", new { id = item.QuestionID }) |
#Html.ActionLink("Delete", "Delete", new { id = item.QuestionID })
</td>
</tr>
}
</table>
Of course, if I can get this to work, I'll need to try and add an action to go back to the controller and update all the records, but I'll just be happy to resolve my current issue.
I would really appreciate any help on this - Thanks!

Answer 1

You need to explicitly create the options in the select tag, using #Html.DropDownList, as follows (taken from a working app):
#Html.DropDownListFor(model => model.IdAccountFrom, ((IEnumerable<FlatAdmin.Domain.Entities.Account>)ViewBag.AllAccounts).Select(option => new SelectListItem {
Text = (option == null ? "None" : option.AccountName),
Value = option.AccountId.ToString(),
Selected = (Model != null) && (option.AccountId == Model.IdAccountFrom)
}), "Choose...")
#Html.ValidationMessageFor(model => model.IdAccountFrom)
You obviously need to change to the properties on your #Model.
NOTE:
This code was auto-generated by the MvcScaffolding NuGet package when I scaffolded a controller.
This package requires you to use Entity Framework Code First POCO classes for your entities. These are easy to generate from an existing database using the Entity Framework Power Tools CTP.
With MVC, you need to spend some time researching the tooling that is out there to help you generate the stuff that you need. Using these tools is a great way to get started and to see how to do things. You can then tweak the output to your heart's content.