MVC 3 #Html.DropDownListFor model binding fails - asp.net-mvc-3

Question

I am using VS 2010 with MVC 3 and EF 5. I am using a common pattern for dropdown lists that works correctly in all but one instance and I cannot see why this one is failing to select the correct entry in the select list. The following are code snippets.
The select list is created as follows:
public static IEnumerable<SelectListItem> GetOutcomes()
{
CodesEntities dataContextCodes = new CodesEntities(ConnectionString);
return new SelectList(dataContextCodes.CodeOutcome.
Where(x => x.DisplayOrder > 0).OrderBy(x => x.DisplayOrder),
"OutcomeCodeID", "Outcome");
}
This returns the correct select list.
The view has the following code:
#Html.DropDownListFor(m => m.OutcomeCodeID,
PerintalFormViewModels.GetOutcomes(), "Please select an item")
The model value m.OutcomeCodeID has a valid value (1) but no item is being selected.
The generated HTML is:
<select id="CodeID" name="OutcomeCodeID" data-val-required="Outcome is required" data-val-number="The field outcome must be a number." data-val="true">
<option value="">Please select an item</option>
<option value="1">Termination</option>
<option value="2">Loss</option>
<option value="3">Still</option>
<option value="4">Live</option>
</select>
I am in the hair tearing out, being driven nuts stage. Does anyone have any thoughts?
Thanks

Answer 1

You can do it like this:
public static IEnumerable<SelectListItem> GetOutcomes(string selectedID)
{
CodesEntities dataContextCodes = new CodesEntities(ConnectionString);
return new SelectList(dataContextCodes.CodeOutcome.
Where(x => x.DisplayOrder > 0).OrderBy(x => x.DisplayOrder),
"OutcomeCodeID", "Outcome"
, selectedID); // add this parameter
}
Or this:
public static IEnumerable<SelectListItem> GetOutcomes(string selectedID)
{
CodesEntities dataContextCodes = new CodesEntities(ConnectionString);
return
dataContextCodes.CodeOutCome
.Where(x => x.DisplayOrder > 0)
.OrderBy(x => x.DisplayOrder)
.ToList()
.Select(x => new SelectListItem
{
Value = x.OutcomeCodeID.ToString(),
Text = x.Outcome.ToString(),
Selected = x.OutcomeCodeID == selectedID
});
}
Then call it like this:
#Html.DropDownListFor(m => m.OutcomeCodeID,
PerintalFormViewModels.GetOutcomes(Model.OutcomeCodeID),
"Please select an item")

Answer 2

You are not setting the default selected value anywhere.
The particular constructor you are using for the SelectList is this one:
public SelectList(
IEnumerable items,
string dataValueField,
string dataTextField
)
Which does not set the default value. Either you use this one:
public SelectList(
IEnumerable items,
string dataValueField,
string dataTextField,
Object selectedValue
)
And specify the selectedValue or you manually set the SelectedListItem's Selected property to true on the item you want selected (http://msdn.microsoft.com/en-us/library/system.web.mvc.selectlistitem(v=vs.108).aspx).
It's a shameless plug but still I think it's a good resource: http://blinkingcaret.wordpress.com/2012/08/11/using-html-dropdownlistfor/