SelectList, ASP.NET MVC

Question

I'm working with a SelectList, and populating it with the data from a table. I'm trying to bind it to the ID of another object.

EDIT Updated the Schema to Reflect something I neglected. I have updated it to show the exact names of each item. I think the problem comes in the fact that each Unit has a sheet, and each sheet has a product. (The sheet will hold more information for the product, but a Unit will have a great deal of other information, so I wanted to separate them in order to keep it clear what was what.)

I think something is happening and the "Sheet" isn't being initialized as an object, and when the binding occurs, it doesn't have an object to bind to, since it is one-level deep. Tell me if this makes sense, or if I am just completely off base.

**Unit**
UnitID (PK)

**ProductSheet**
UnitId (FK)(PK)
ItemId (FK)

**Items**
ItemId (PK)
ItemTitle

It just ...isn't working though. I have this code.

DatabaseDataContext db = new DatabaseDataContext();
Unit unit = new Unit();
ViewData["Items"] = new SelectList( db.Items, "Id", "ItemTitle", unit.ProductSheet.ItemId);

But in the postback, the selectList is always null and empty! This is the View code. I'm really getting lost here, I've followed a lot of examples and it still comes up with bunk.

<%= Html.DropDownList("Items") %>

Answer 1

Your view code should read:

<% var selectItems = ViewData["Items"] as SelectList; %>
<%= Html.DropDownList("ProductSheet.ItemId", selectItems) %>

Answer 2

An entire sample of the project is available at this url

These are the action methods.

public ActionResult Create()
{
  DatabaseDataContext database = new DatabaseDataContext();
  Unit u = new Unit();
  u.Sheet = new Sheet();
  ViewData["ProductListing"] = new SelectList(database.Products, "ProductId", "ProductName", u.Sheet.ProductId);
    return View();
} 

//
// POST: /Home/Create

[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Create(Unit u)
{
    try
  {
   DatabaseDataContext database = new DatabaseDataContext();
   database.Units.InsertOnSubmit(u);
   database.SubmitChanges();
        // TODO: Add insert logic here

        return RedirectToAction("Index");
    }
    catch
    {
        return View();
    }
}

Here is the Create View.

<%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<MVC.Models.Contexts.Unit>" %>

<asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server">
    Create
</asp:Content>

<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">

    <h2>Create</h2>

    <%= Html.ValidationSummary("Create was unsuccessful. Please correct the errors and try again.") %>

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

        <fieldset>
            <legend>Fields</legend>
            <%= Html.DropDownList("ProductListing") %>
            <p>
                <input type="submit" value="Create" />
            </p>
        </fieldset>

    <% } %>

    <div>
        <%=Html.ActionLink("Back to List", "Index") %>
    </div>

</asp:Content>

<asp:Content ID="Content3" ContentPlaceHolderID="ScriptContent" runat="server">
</asp:Content>

Answer 3

I've marked the answer that seems to have made some progress now, I think I'm starting to understand it better.

When I passed the 'path' of the object to assign as a string in the name field of DropDownList, it seems to work. But this doesn't really make a lot of sense to me. Can you explain what is going on any better?