Question

I am having an issue where the item in the dropdown list is not being selected. I am building up an array of SelectListItems and setting the right one to selected = true but its not getting selected.

I have the following code in my controller:

    public ActionResult Edit(int id)
    {
        var p = _myRepository.FindBy(id);
        var vm = new MyViewModel(p) { CategoryTypes = ControllerUtils.GetList(_myTypeRepository, r => r.Name, p.CategoryType.Id) };

        return View(vm);
    }

and here is the GetList function in the ControllerUtils class:

public static class ControllerUtils
{
    public static IEnumerable<SelectListItem> GetList<T>(IIntKeyedRepository<T> list, Func<T, string> getName, int id) where T : BaseModel
    {
        var items = list.All().ToList();
        var itemsList = items.Select(r => new SelectListItem() { Selected = r.Id == id, Text = getName(r), Value = r.Id.ToString() });
        return itemsList;
    }
}

and here is my view code:

    <div class="editor-label">
        @Html.LabelFor(model => model.MyObject.CategoryType)
    </div>
    <div class="editor-field">
        @Html.DropDownListFor(model => model.MyObject.CategoryType, Model.CategoryTypes)
        @Html.ValidationMessageFor(model => model.MyObject.CategoryType)
    </div>

When i debug in the controller code and list into the array of SelectListItem objects i do see the second item has selected = true. But when i check the view HTML, I don’t see either item being selected:

<select id="CategoryType" name="CategoryType">
  <option value="1">Choice 1</option>
  <option value="2">Choice 2</option>
</select>

As you can see, there is no “selected=”selected” for either item. Any suggestions on what could be going on here?

Answer 1

The first argument of the DropDownListFor helper must be a lambda expression pointing to a primitive type property on your view model containing the selected value:

@Html.DropDownListFor(
    model => model.MyObject.CategoryType.Id, 
    Model.CategoryTypes
)

Now get rid of the Selected = r.Id == id property inside your SelectListItem. You don’t need it. Now assuming that Model.MyObject.CategoryType.Id has a corresponding item with matching value inside Model.CategoryTypes the helper will automatically preselect this item.