title: Entity 5/6 Model first: do I have to manually map entities?
body: <p>When I first created my .edmx, I added a single entity. I then selected "Generate database from model" and successfully created my database and did some testing with that single entity/table and some dummy data.</p>
  
  <p>I'm working on my model again, and I've added a number of other tables and associations. When I select "Generate database from model" now, I get lots of errors about things not being mapped (including the new scalar properties on my original entity), as well as a message box showing the following error:</p>
  
  <blockquote>
    <p>Expression of type
    'System.Data.Entity.Core.Metadata.Edm.EdmItemCollection' cannot be
    used for return type
    'System.Data.Entity.Core.Metadata.Edm.EdmItemCollection'.</p>
  </blockquote>
  
  <p>Why would generating the database work the first time with a single entity (without me ever explicitly declaring any mapping for table or columns), but not with multiple entities added after the original? Do I need to manually map everything (doesn't seem likely, but I must be missing something)?</p>