Trying to edit an entity with data from dropdowns in MVC

I'm having trouble getting my head around sending multiple models to a view in mvc. My problem is the following.

Using EF4 I have a table with attributes organised by category.

Couldn't post an image :-( [Have a table called attributes (AttributeTitle, AttributeName, CategoryID) connected to a table called Category (CategoryTitle).]

What I want to do is be able to edit an attribute entity and have a dropdown of categories to choose from.

I tried to make a custom viewmodel

    public class AttributeViewModel
{
    public AttributeViewModel()
    {
    }

    public Attribute Attribute { get; set; }
    public IQueryable<Category> AllCategories { get; set; }
}

But it just ended up being a mess.

<div class="editor-field">
        <%: Html.DropDownList("Category", new SelectList((IEnumerable)Model.AllCategories, "CategoryID", "CategoryName")) %>
    </div>

I was getting it back to the controller...

        [HttpPost]
    public ActionResult Edit(int AttributeID, FormCollection formcollection)
    {
        var _attribute = ProfileDB.GetAttribute(AttributeID);
        int _selcategory = Convert.ToInt32(formcollection["Category"]);
        _attribute.CategoryID = (int)_selcategory;

        try
        {
            UpdateModel(_attribute); (<---Error here)
            ProfileDB.SaveChanges();

            return RedirectToAction("Index");
        }
        catch (Exception e)
        {

            return View(_attribute);
        }
    }

I've debugged the code and my _attribute looks correct and _attribute.CategoryID = (int)_selcategory updates th开发者_StackOverflowe model, but then I get the error.

Somewhere here I thought that there should be a cleaner way to do this, and that if I could only send two models to the view instead of having to make a custom viewmodel.

To sum it up: I want to edit my attribute and have a dropdown of all of the available categories.

Any help much appreciated!

Solved it!

If anyone is interested, my solution is the following. I created a class:

public class AttributeEditViewModel
{
    public AttributeEditViewModel()
    {
    }

    public AttributeEditViewModel(Attribute attribute, SelectList categories)
    {
        this.attribute = attribute;
        this.categories = categories;
    }

    public Attribute attribute { get; set; }
    public SelectList categories { get; set; }
}

My controller:

        // GET: /Attribute/Edit/5
    public ActionResult Edit(int AttributeID)
    {
        Attribute _attribute = ProfileDB.GetAttribute(AttributeID);

        var _viewmodel = new AttributeEditViewModel
        {
            attribute = _attribute,
            categories = new SelectList(ProfileDB.GetAllCategories(), "CategoryID", "CategoryName", _attribute.CategoryID)
        };

        return View(_viewmodel);
    }

Part of my view:

<%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<KnowledgePortal.ViewModel.AttributeEditViewModel>" %>



<div class="editor-field">
     <%: Html.DropDownList("Category", Model.categories, Model.attribute.CategoryID) %>
</div>

<p>
     <input type="submit" value="Save" />
</p>

And the postback:

// POST: /Attribute/Edit/5
[HttpPost]
public ActionResult Edit(int AttributeID, FormCollection formcollection)
{
    var _attribute = ProfileDB.GetAttribute(AttributeID);
    int _selcategory = Convert.ToInt32(formcollection["Category"]);
    _attribute.CategoryID = (int)_selcategory;

    try
    {
        ProfileDB.SaveChanges();

        return RedirectToAction("Index");
    }
    catch (Exception e)
    {

        return View(_attribute);
    }
}

Basically my problem was due to my lack of understanding what updatemodel did. So after "_attribute.CategoryID = _selcategory" all I had to do was savechanges, but first I tried to updatemodel which kept failing.

Hope this helps someone else!