EF Navigation Properties and Saves - entity-framework

Question

Suppose I have these two POCOs:
public class Album {
public int ID { get; set; }
[Required]
public string Title { get; set; }
public short Rating { get; set; }
public int ArtistID { get; set; }
[Required]
public virtual Artist Artist { get; set; }
}
public class Artist {
public int ID { get; set; }
[Required]
public string Name { get; set; }
public virtual ICollection<Album> Albums { get; set; }
}
and then I execute some code like this:
using (PickContext db=new PickContext()) {
Album pick=db.Albums.SingleOrDefault(a => a.ID==pickID);
if (pick==null) return;
pick.Rating=4;
db.SaveChanges();
I was surprised that I got a validation exception like this:
Property: "Artist", Error: "The Artist field is required."
When I changed my query to include the Artist:
Album pick=db.Albums.Include("Artist").SingleOrDefault(a => a.ID==pickID);
I no longer got the exception. If I don't tell EF to populate all properties, and they're not required, will it simply overwrite these FKs in the database? I would have thought that if I retrieve an entity and don't assign a property, the property won't be changed in the database. Is this not true?

Answer 1

You don't need to use the required attribute for the Artist. It simply telling to EF your navigation property is always required to be there. Since you have defined,
public int ArtistID { get; set; }
as not nullable the ArtistID will be required in the in the database level (I think that is what you expected from the required attribute here). I think you can just remove the required attribute and then this should be working as expected.