asp.net mvc - There is no ViewData item of type 'IEnumerable<SelectListItem>' that has the key 'xxx'

Question

There are a couple of posts about this on Stack Overflow but none with an answer that seem to fix the problem in my current situation.

I have a page with a table in it, each row has a number of text fields and a dropdown. All the dropdowns need to use the same SelectList data so I have set it up as follows:

Controller

ViewData["Submarkets"] = new SelectList(submarketRep.AllOrdered(), "id", "name");

View

<%= Html.DropDownList("submarket_0", (SelectList)ViewData["Submarkets"], "(none)") %>

I have used exactly this setup in many places, but for some reason in this particular view I get the error:

There is no ViewData item of type 'IEnumerable' that has the key 'submarket_0'.

Answer 1

Ok, so the answer was derived from some other posts about this problem and it is:

If your ViewData contains a SelectList with the same name as your DropDownList i.e. "submarket_0", the Html helper will automatically populate your DropDownList with that data if you don't specify the 2nd parameter which in this case is the source SelectList.

What happened with my error was:

Because the table containing the drop down lists was in a partial view and the ViewData had been changed and no longer contained the SelectList I had referenced, the HtmlHelper (instead of throwing an error) tried to find the SelectList called "submarket_0" in the ViewData (GRRRR!!!) which it STILL couldnt find, and then threw an error on that :)

Please correct me if im wrong