DropDownListFor Not Selecting Value

Question

I\'m using the DropDownListFor helper method inside of an edit page and I\'m not having any luck getting it to select the value that I specify. I noticed a similar question

Answer 1

I had the same problem. In the example below The variable ViewData["DATA_ACREDITO_MODELO_INTEGRADO"] has a SelectListItem list with a default selected value but such attribute is not reflected visually.

// data 
        var p_estadoAcreditacion = "NO";
        var estadoAcreditacion = new List<SelectListItem>();
        estadoAcreditacion.Add(new SelectListItem { Text = "(SELECCIONE)"    , Value = " "    });
        estadoAcreditacion.Add(new SelectListItem { Text = "SI"              , Value = "SI"   });
        estadoAcreditacion.Add(new SelectListItem { Text = "NO"              , Value = "NO"   });

        if (!string.IsNullOrEmpty(p_estadoAcreditacion))
        {
            estadoAcreditacion.First(x => x.Value == p_estadoAcreditacion.Trim()).Selected = true;
        }
         ViewData["DATA_ACREDITO_MODELO_INTEGRADO"] = estadoAcreditacion;

I solved it by making the first argument of DropdownList, different to the id attribute.

// error:
@Html.DropDownList("SELECT__ACREDITO_MODELO_INTEGRADO"
, ViewData["DATA_ACREDITO_MODELO_INTEGRADO"] as List<SelectListItem>
, new
{
id         = "SELECT__ACREDITO_MODELO_INTEGRADO"
...
// solved :
@Html.DropDownList("DROPDOWNLIST_ACREDITO_MODELO_INTEGRADO"
, ViewData["DATA_ACREDITO_MODELO_INTEGRADO"] as List<SelectListItem>
, new
{
id         = "SELECT__ACREDITO_MODELO_INTEGRADO"

...

Answer 2

I encountered this issue recently. It drove me mad for about an hour. In my case, I wasn't using a ViewBag variable with the same name as the model property.

After tracing source control changes, the issue turned out to be that my action had an argument with the same name as the model property:

public ActionResult SomeAction(string someName)
{
    var model = new SomeModel();
    model.SomeNames = GetSomeList();
    //Notice how the model property name matches the action name
    model.someName = someName; 
}

In the view:

@Html.DropDownListFor(model => model.someName, Model.SomeNames)

I simply changed the action's argument to some other name and it started working again:

public ActionResult SomeAction(string someOtherName)
{
    //....
}

I suppose one could also change the model's property name but in my case, the argument name is meaningless so...

Hopefully this answer saves someone else the trouble.

Answer 3

One other thing to check if it's not all your own code, is to make sure there's not a javascript function changing the value on page load. After hours of banging my head against a wall reading through all these solutions, I discovered this is what was happening with me.

Answer 4

After researching for an hour, I found the problem that is causing the selected to not get set to DropDownListFor. The reason is you are using ViewBag's name the same as the model's property.

Example

public  class employee_insignia
{ 
   public int id{get;set;}
   public string name{get;set;}
   public int insignia{get;set;}//This property will store insignia id
}

// If your ViewBag's name same as your property name 
  ViewBag.Insignia = new SelectList(db.MtInsignia.AsEnumerable(), "id", "description", 1);

View

 @Html.DropDownListFor(model => model.insignia, (SelectList)ViewBag.Insignia, "Please select value")

The selected option will not set to dropdownlist, BUT When you change ViewBag's name to different name the selected option will show correct.

Example

ViewBag.InsigniaList = new SelectList(db.MtInsignia.AsEnumerable(), "id", "description", 1);

View

 @Html.DropDownListFor(model => model.insignia, (SelectList)ViewBag.InsigniaList , "Please select value")

Answer 5

The issue at least for me was tied to the IEnumerable<T>.

Basically what happened was that the view and the model did not have the same reference for the same property.

If you do this

IEnumerable<CoolName> CoolNames {get;set;} = GetData().Select(x => new CoolName{...});}

Then bind this using the

@Html.DropDownListFor(model => model.Id, Model.CoolNames)

The View loses track of the CoolNames property, a simple fix is just to add .ToList() After dooing a projection (.Select()) ;).