Question

I am using DropDownListFor to render a dropdown list in a view. Somehow the rendered list does not select the SelectListItem with Selected set to true.

In the controller action:

var selectList = sortedEntries.Select(entry => new SelectListItem
                            {
                                Selected = entry.Value.Equals(selectedValue),
                                Text = entry.Value,
                                Value = entry.Id
                            });

return View(new DropDownListModel
            {
                ListId = id,
                SelectList = selectList,
                OptionLabel = "Click to Select"
            });

In the view:

<%= Html.DropDownListFor(m => m.ListId, 
    Model.SelectList, 
    Model.OptionLabel, 
    new {@class="someClass"}) %>

I have tried the following:

1. make sure that there is one and only one items with Selected set to true.
2. remove the option label argument.
3. remove the HTML attribute object.
4. use SelectList in DropDownListFor:

---

   Html.DropDownListFor(m => m.ListId, 
        new SelectList(Model.SelectList, "Value", "Text", 
             new List<SelectListItem>(Model.SelectList).Find(s => s.Selected)), 
        new {@class="someClass"})

Any suggestions as to what went wrong?

EDIT:

more information:

• This action is a child action, called by another view with HTML.RenderAction

Answer 1

Try like this:

var selectList = sortedEntries.Select(entry => new SelectListItem
{
    Text = entry.Value,
    Value = entry.Id
});

return View(new DropDownListModel
{
    // The drop down list is bound to ListId so simply set its value
    // to some element value in the list and it will get automatically
    // preselected
    ListId = selectedValue, 
    SelectList = selectList,
    OptionLabel = "Click to Select"
});

and in the view:

<%= Html.DropDownListFor(
    m => m.ListId, 
    new SelectList(Model.SelectList, "Value", "Text"), 
    Model.OptionLabel, 
    new { @class = "someClass" }
) %>

There could be one more gotcha: you are trying to change the selected value in a POST action. For example you rendered a form, the user selected some value in the dropdown, submitted the form and in your POST action you do some processing on this selected value and when you redisplay the view you want the drop down list to have some other value selected. In this case you will have to remove the initial selection which is contained in the ModelState or the Html helper will ignore the selected value in the model:

// do this before returning the view and only if your scenario
// corresponds to what I described above
ModelState.Remove("ListId");