entity framework - EF Navigation Properties and Saves -

suppose have these 2 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 execute code 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 surprised got validation exception this:

property: "artist", error: "the artist field required."

when changed query include artist:

       album pick=db.albums.include("artist").singleordefault(a => a.id==pickid); 

i no longer got exception. if don't tell ef populate properties, , they're not required, overwrite these fks in database? have thought if retrieve entity , don't assign property, property won't changed in database. not true?

you don't need use required attribute artist. telling ef navigation property required there. since have defined,

public int artistid { get; set; } 

as not nullable artistid required in in database level (i think expected required attribute here). think can remove required attribute , should working expected.