R – HTML.DropDownList does not respect pre-selected value

asp.net-mvcdrop-down-menu

I want to use Html.DropDownList(string name, IEnumerable SelectList, Object htmlAttributes) to render a select list with a preselected value for me.

My select list is in the model object of my view, so I have been writting the following code:

<%= Html.DropDownList("aName", mySelectList, new { }) %>

Which will render the select list without the pre-selected value.

A workaround I have found is passing the SelectList as ViewData and doing the following:

In the controller:

ViewData["TimeZones"] = mySelectList;

In the view:

<%= Html.DropDownList("TimeZones", null, new { }) %>

This way the select list will be rendered with the preselected value, however, I don't want to be forced to pass my select list as view data. What am I doing wrong? Thank you in advance for your help.

Best Answer

You can simply do this (it works):

<%: Html.DropDownList("DropdownName", new SelectList(ListItems, "Value", "Text", selectedItem), htmlAttributes)%>

Let me know in case this does not work for you.

Related Solutions

Asp.net-mvc – ASP.NET MVC – Html.DropDownList – Value not set via ViewData.Model

Actually, you just have to pass in null for the Html.DropDownList().
I was having the same exact problem, and used the Reflector to look at the MVC Source Code.

In the System.Web.Mvc.Extensions.SelectExtensions class's SelectInternal() method, it checks whether the selectList parameter is null or not. If it is passed in as null, it looks up the SelectList properly.

Here is the "Code-behind".

ViewData["MyDropDown"] = new SelectList(selectListItems,
                             "Value",
                             "Text",
                             selectedValue.ToString()
                         );

Here is the HTML view code.

<%= Html.DropDownList("MyDropDown", null,
        "** Please Select **",
        new { @class = "my-select-css-class" }
    ) %>

Note: I'm using ASP.NET MVC 2.0 (Beta Version).

UPDATE NOTE: January 31st 2012

After extensively using ASP.NET MVC for the past 3 years, I prefer using additionalViewData from the Html.EditorFor() method more.

Pass in your [List Items] as an anonymous object with the same property name as the Model's property into the Html.EditorFor() method.

<%= Html.EditorFor(
    m => m.MyPropertyName,
    new { MyPropertyName = Model.ListItemsForMyPropertyName }
) %>

If you want more details, please refer to my answer in another thread here.

Asp.net-mvc – ASP.NET MVC Html.DropDownList SelectedValue

This is how I fixed this problem:

I had the following:

Controller:

ViewData["DealerTypes"] = Helper.SetSelectedValue(listOfValues, selectedValue) ;

View

<%=Html.DropDownList("DealerTypes", ViewData["DealerTypes"] as SelectList)%>

Changed by the following: