Question

I have looked through a ton of tutorials and suggestions on how to work with DropDownList in MVC. I was able to get most of it working, but the selected item is not saving into the database. I am using MVC 3 and Razor for the view.

My DropDownList is getting created with the correct values and good looking HTML. When I set a breakpoint, I can see the correct selected item ID in the model getting sent to controller. When the view goes back to the index, the DropDownList value is not set. The other values save just fine.

Here are the related views. The DropDownList is displaying a list of ColorModel names as text with the ID as the value.

public class ItemModel
{
    [Key]
    public int ItemID { get; set; }
    public string Name { get; set; }
    public string Description { get; set; }
    public virtual ColorModel Color { get; set; }
}
public class ItemEditViewModel
{
    public int ItemID { get; set; }
    public string Name { get; set; }
    public string Description { get; set; }
    public int ColorID { get; set; }
    public IEnumerable<SelectListItem> Colors { get; set; }
}
public class ColorModel
{
    [Key]
    public int ColorID { get; set; }
    public string Name { get; set; }
    public virtual IList<ItemModel> Items { get; set; }
}

Here are the controller actions.

    public ActionResult Edit(int id)
    {
        ItemModel itemmodel = db.Items.Find(id);
        ItemEditViewModel itemEditModel;
        itemEditModel = new ItemEditViewModel();
        itemEditModel.ItemID = itemmodel.ItemID;
        if (itemmodel.Color != null) {
            itemEditModel.ColorID = itemmodel.Color.ColorID;
        }
        itemEditModel.Description = itemmodel.Description;
        itemEditModel.Name = itemmodel.Name;
        itemEditModel.Colors = db.Colors
            .ToList()
            .Select(x => new SelectListItem
                {
                    Text = x.Name,
                    Value = x.ColorID.ToString()
                });
        return View(itemEditModel);
    }

    [HttpPost]
    public ActionResult Edit(ItemEditViewModel itemEditModel)
    {
        if (ModelState.IsValid)
        {
            ItemModel itemmodel;
            itemmodel = new ItemModel();
            itemmodel.ItemID = itemEditModel.ItemID;
            itemmodel.Color = db.Colors.Find(itemEditModel.ColorID);
            itemmodel.Description = itemEditModel.Description;
            itemmodel.Name = itemEditModel.Name;
            db.Entry(itemmodel).State = EntityState.Modified;
            db.SaveChanges();
            return RedirectToAction("Index");
        }
        return View(itemEditModel);
    }

The view has this for the DropDownList, and the others are just EditorFor().

@Html.DropDownListFor(model => model.ColorID, Model.Colors, "Select a Color")

When I set the breakpoint on the db.Color.Find(...) line, I show this in the Locals window for itemmodel.Color:

{System.Data.Entity.DynamicProxies.ColorModel_0EB80C07207CA5D88E1A745B3B1293D3142FE2E644A1A5202B90E5D2DAF7C2BB}

When I expand that line, I can see the ColorID that I chose from the dropdown box, but it does not save into the database.

Answer 1

You do not need to set the whole Color object. Just set the ColorId property.

Change

itemmodel.Color = db.Colors.Find(itemEditModel.ColorID);

To

itemmodel.ColorId = itemEditModel.ColorID;

Edit

Note that your database does not store the whole object. The Color object in ItemModel is just a convenient way to access the ColorModel entity that is assosiated by a foreign key.

According to convention, the name of the foreign key property should be ColorId. Add this int property in your ItemModel class.