DropDownListFor - does not select "Selected" value

Question

Another one of these questions regarding DropDownListFor not selecting the "Selected" value. Here is code:

Model:

public class CreateEditAccountModel
{
    [Required]
    [Display(Name = "Permission")]
    public int PermissionId { get; set; }
    public IEnumerable<SelectListItem> Permissions { get; set; }
}

Controller:

[HttpGet]
[Authorize]
public ActionResult EditAccount(int id)
{
    CreateEditAccountModel model = new CreateEditAccountModel();
    model.Permissions = PermissionsAll();
    return View("CreateEditAccount", model);
}

At this point if I put a break point on return line, the model.Permissions contains proper IEnumerable<SelectListItem> object with multiple items and only one, that has Selected = true.

View:

@using (Html.BeginForm())
{
    @Html.DropDownListFor(m => m.PermissionId, Model.Permissions)
}

Renders:

<select id="PermissionId" name="PermissionId">
    <option value="">-- Select --</option>
    <option value="1">Permission one</option>
    <option value="2">Permission two</option>
</select>

For some reason there is no selected attribute on any of the options and first option is selected.

Any help is appreciated.

---

UPDATE

It appears it has something to do with this article. To summarize the solution of this article, I need to make sure that the property name (first argument of @html.DropDownList) does not match any existing properties of the model. Can anybody explain why this is the case?

It renders drop down correctly when I write in the view something like this:

@Html.DropDownList("PermissionIdNotMatching", Model.Permissions)

However, it does not make any logical sense to do it since I actually want binder to be able to match the name of the select element to the model property. Otherwise I'd have to manually grab the value like this: Request.Form["PermissionIdNotMatching"];

Anybody have any thoughts?

---

SOLUTION

See accepted answer and the first comment to it.

Answer 1

Ok, let's discuss about your example, when PermissionId was int. You posted model of type CreateEditAccountModel to view. When you created this model, PermissionId equal 0 (default value of int). And DropDownListFor in view get this value. Therefore you had no selected values. When you used string type, default value of PermissionId was null, therefore `DropDownListFor taken default value of SelectList.

In this case it's better to use int? or Nullable<int> type for PermissionId.

Answer 2

When you use @Html.DropDownListFor(m => m.PermissionId, Model.Permissions), please ensure the PermissionId is already set in your Model - that is the selected item / id. In addition, the model contains a 'selected' attribute:

var query = DatabaseContexts.Select(
            c => new SelectListItem
            {
                Value = c.Key,
                Text = c.Value,
                Selected = c.Key == currentUsed
            });

 PermissionId = that want to select;
 Permissions = query.AsEnumerable();

UPDATE:

here is a full sample of HttpGet:

In HomeController.cs:

[HttpGet]
public ActionResult EditAccount(int id)
{
    CreateEditAccountModel model = new CreateEditAccountModel();

    var permissionsAll = new List<SelectListItem>
         {
             new SelectListItem
                 {
                     Value = "",
                     Text = "--please select--",
                     Selected = false
                 },
             new SelectListItem
                 {
                     Value = "1",
                     Text = "Permission one",
                     Selected = true
                 },
             new SelectListItem
                 {
                     Value = "2",
                     Text = "Permission two",
                     Selected = false
                 }
         };
    model.PermissionId = 1; //add this line
    model.Permissions = permissionsAll; // PermissionsAll();// -- get data from services or anywhere....
    return View("EditAccount", model);
}

CreateEditAccountModel.cs:

public class CreateEditAccountModel
{
    [Required]
    [Display(Name = "Permission")]
    public int PermissionId { get; set; }
    public IEnumerable<SelectListItem> Permissions { get; set; }

}

EditAccount.cshtml:

@using MvcApplication1.Models
@model CreateEditAccountModel
@{
   ViewBag.Title = "EditAccount";
 }

<h2>EditAccount</h2>
@using (Html.BeginForm())
{
   @Html.DropDownListFor(m => m.PermissionId, Model.Permissions)
}

Run the application and go to /home/editaccount/1, the dropdown will select "Permission one" by default.

I think the PermissionId must be type 'string' is, System.Web.Mvc.SelectedListItem.Value is 'string'

If you would like to do something when user selected item in the dropdown list, you may need [HttpPost].

BTW: this link is useful to you?