Getting SelectedValue back from a DropDown in ASP.NET MVC (C#) using Entity Framework

Question

Sorry if this is a repeated question, I scanned the related questions and didn't see anything obvious.

I'm using an EditModel with an Entity object, along with two SelectLists in it. The problem is, once I reach my POST action, the SelectedValues for both drop downs are still the same default values I set in the constructor for the model, no matter what I actually select on the browser.

My constructor sets some default values for the SelectedValues, but they are just 0 and "" (which aren't valid values in the dropdowns). I have a feeling the problem revolves around that somehow, but I'll give more details.

Here is a stripped down version of the model:

public class UserAccountModel 
{

    public UserAccount UserAccountData { get; set; } // Entity from EF
    public SelectList Organizations { get; set; }
    public SelectList Roles { get; set; }

    public UserAccountModel() : this(null)
    {
    }


    public UserAccountModel(UserAccount obj)
    {
        UserAccountData = (obj == null) ? new UserAccount() : obj;

        // default selected value
        int orgChildId = (UserAccountData.Organization == null) ? 0 : UserAccountData.Organization.ID;
        string roleChildId = (UserAccountData.Role == null) ? "" : UserAccountData.Role.Name;

        // go get the drop down options and set up the property binding
        using (UserAccountRepository rep = new UserAccountRepository())
        {
            Organizations = new SelectList(rep.GetOrganizationOptions(), "ID", "ID", orgChildId);
            Roles = new SelectList(rep.GetRoleOptions(), "ID", "Name", roleChildId);
        }
    }

    public void UpdateModel()
    {
        UserAccountData.Organization = Organizations.SelectedValue as Organization;
        UserAccountData.Role = Roles.SelectedValue as Role;
    }
}

This is the Dropdowns portion of the view:

                <div class="field">
                <label for="ID">Organization:</label>
                <%= Html.DropDownList("ID", Model.Organizations) %>
   </div>

            <div class="field">
                <label for="Name">Role:</label>
                <%= Html.DropDownList("Name", Model.Roles) %>
   </div>

I might have done something stupid and obvious here. The examples are much more straight forward when using the ViewData dictionary, but I couldn't find too many examples trying to use straight model binding for SelectLists.

Any help is greatly appreciated!

Chris

Answer 1

You simply forgot the navigational path to the ID property :)

<%= Html.DropDownList("Organization.ID", Model.Organizations) %>

Answer 2

Select elements only post back the actual value of the selected it. In this case, the parameters will be received back at the server/controller as ID (organization) and Name (role). The model you use for the update action should either contain these as properties or your controller action should accept them directly as parameters. The lists on the model won't be repopulated -- and the names don't match in any event.

Modify your model by adding:

public int ID { get; set; }
public string Name { get; set; }

with controller action as:

public ActionResult Update( UserAccountModel userAccount )
{
    ...
}

Note that if there is a validation error, you'll need to repopulate the SelectList properties (reconstituting the menus).