Retrieving data from Html.DropDownList() in controller (ASP MVC) | string returned?

Question

I have the following problem:

I have a form in site/banen (currently local running webserver) which is using a SQL database. The link is made using ADO.net and is instantiated in the controller in the following way:

DBModelEntities _entities;
_entities = new DBModelEntities(); // this part is in the constructor of the controller.

Next, I use this database to fill a Html.DropDownList() in my view. This is done in two steps. At the controller side we have in the constructor:

ViewData["EducationLevels"] = this.GetAllEducationLevels();

and a helper method:

public SelectList GetAllEducationLevels()
{
     List<EducationLevels> lstEducationLevels = _entities.EducationLevels.ToList();
     SelectList slist = new SelectList(lstEducationLevels, "ID", "Name");
     return slist;
}

In the view I have the following:

<% using (Html.BeginForm()) {%>

    <fieldset>
        <legend>Fields</legend>

        <!-- various textfields here -->

        <p>
            <label for="EducationLevels">EducationLevels:</label>
            <!-- <%= Html.DropDownList("EducationLevels", ViewData["EducationLevels"] as SelectList)%> -->
            <%= Html.DropDownList("EducationLevels", "..select option..")%>
        </p>
        <p>
            <input type="submit" value="Create" />
        </p>
    </fieldset>

<% } %>

Now, the form is rendered correctly when I browse to the create page. I can select etc. But when selected I have to use that value to save in my new model to upload to the database. This is where it goes wrong. I have the following code to do this in my controller:

//
    // POST: /Banen/Create

    [AcceptVerbs(HttpVerbs.Post)]
    public ActionResult Create(FormCollection form)
    {
        // set rest of information which has to be set automatically
        var vacatureToAdd = new Vacatures();
        //vacatureToAdd.EducationLevels = form["EducationLevels"];

        // Deserialize (Include white list!)
        TryUpdateModel(vacatureToAdd);

        // Validate
        if (String.IsNullOrEmpty(vacatureToAdd.Title))
            ModelState.AddModelError("Title", "Title is required!");
        if (String.IsNullOrEmpty(vacatureToAdd.Content))
            ModelState.AddModelError("Content", "Content is required!");

        // Update the variables not set in the form
        vacatureToAdd.CreatedAt = DateTime.Now;                 // Just created.
        vacatureToAdd.UpdatedAt = DateTime.Now;                 // Just created, so also modified now.
        vacatureToAdd.ViewCount = 0;                            // We have just created it, so no views
        vacatureToAdd.ID = GetGuid();                           // Generate uniqueidentifier

        try
        {
            // TODO: Add insert logic here
            _entities.AddToVacatures(vacatureToAdd);
            _entities.SaveChanges();

            // Return to listing page if succesful
            return RedirectToAction("Index");
        }
        catch (Exception e)
        {
            return View();
        }
    } 
    #endregion

It gives the error:

alt text http://www.bastijn.nl/zooi/error_dropdown.png

I have found various topics on this but all say you can retrieve by just using:

vacatureToAdd.EducationLevels = form["EducationLevels"];

Though this returns a string for me. Since I'm new to ASP.net I think I am forgetting to tell to select the object to return and not a string. Maybe this is the selectedValue in the part where I make my SelectList but I can't figure out how to set this correctly. Of course I can also be complete on a sidetrack.

Sidenote: currently I'm thinking about having a seperate model like here.

Any help is appreciated.

Answer 1

You can't return an object from usual <SELECT> tag wich is rendered by Html.DropDownList() method, but only string variable could be returned. In your case ID of EducationLevels object will be send to the server. You should define and use one more custom helper method to reconstruct this object by ID.