Não consigo gerar DropDownList no HTML

Estou trabalhando uma aplicação MVC 2 com Entity FrameWork para estudos, pois estou começando. O problema ocorre quando tento gerar uma página com o dados vindo do BD, porém há dois campos que são listas,  para o preenchimento de um DropDownList. Dois no caso. Os campos são gerados porém somente com TextBox. Uso VS2010 Ultimate. O que poderia estar errado? Segue o código!!   StoreManagerViewModel.cs. On the folder ViewModels using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using MvcMusicStore.Models; namespace MvcMusicStore.ViewModel
{
    public class StoreManagerViewModel
    {
        public Album Album { get; set; }
        public List<Artist> Artists { get; set; }
        public List<Genre> Genres { get; set; }
    }
} StoreManagerController.cs. On the folder Controllers         public ActionResult Edit(int id)
        {
            var viewModel = new StoreManagerViewModel()
            {
                Album = storeDB.Albums.Single(a => a.AlbumId == id),
                Genres = storeDB.Genres.ToList(),
                Artists = storeDB.Artists.ToList()
            };             return View(viewModel);
        }
Edit.aspx. On the folder ~\Views\StoreManager <%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<MvcMusicStore.ViewModel.StoreManagerViewModel>" %> <asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server">
    Edit -
    <%: Model.Album.Title %>
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">
    <form id="form1" runat="server">
    <h2>
        [ Edit ]
    </h2>
    <% using (Html.BeginForm())
       {%>
    <%: Html.ValidationSummary(true) %>
    <fieldset>
        <legend>Edit Album</legend>
        <%: Html.EditorFor(model => model.Album, new { Artists = Model.Artists, Genres = Model.Genres })%>
        <p>
            <input type="submit" value="Save" />
        </p>
    </fieldset>
    <% } %>
    <div>
        <%: Html.ActionLink("Back to List", "Index") %>
    </div>
    </form>
</asp:Content>
Album.ascx. On the folder ~\Views\Shared\EditorTemplate
<%@ Import Namespace="MvcMusicStore" %>
<%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<MvcMusicStore.Models.Album>" %>
<p>
    <%: Html.LabelFor(model => model.Title)%>
    <%: Html.TextBoxFor(model => model.Title)%>
    <%: Html.ValidationMessageFor(model => model.Title)%>
</p>
<p>
    <%: Html.LabelFor(model => model.Price)%>
    <%: Html.TextBoxFor(model => model.Price)%>
    <%: Html.ValidationMessageFor(model => model.Price)%>
</p>
<p>
    <%: Html.LabelFor(model => model.AlbumArtUrl)%>
    <%: Html.TextBoxFor(model => model.AlbumArtUrl)%>
    <%: Html.ValidationMessageFor(model => model.AlbumArtUrl)%>
</p>
<p>
    <%: Html.LabelFor(model => model.Artist)%>
    <%: Html.DropDownList("ArtistId", new SelectList(ViewData["Artists"] as IEnumerable, "ArtistId", "Name", Model.ArtistId))%>
</p>
<p>
    <%: Html.LabelFor(model => model.Genre)%>
    <%: Html.DropDownList("GenreId", new SelectList(ViewData["Genres"] as IEnumerable, "GenreId", "Name", Model.GenreId))%>
</p>