Proxy's First Navigation Property is null when Seeding EF 4.1

问题

When Initializer.Seed() uses DbContext.DbSet.Find() to set the navigation properties for a new Proxy, it correctly assigns the FK's to the Proxy, but the first navigation property is always null when I break on SaveChanges() and inspect the Proxy. Does anyone know why it does this?

(Sorry, I can't post a screenshot of the locals window.)

Model

public class Thing : Base {
    public virtual Nullable<int> Option1ID { get; set; }
    public virtual Option1 Option1 { get; set; }
    public virtual Nullable<int> Option2ID { get; set; }
    public virtual Option2 Option2 { get; set; }
    public virtual Nullable<int> Option3ID { get; set; }
    public virtual Option3 Option3 { get; set; }
}
public class Option1 : Base {
    public virtual ICollection<Thing> Things { get; set; }
}
public class Option2 : Base {
    public virtual ICollection<Thing> Things { get; set; }
}
public class Option3 : Base {
    public virtual ICollection<Thing> Things { get; set; }
}
public class Base {
    public virtual int Id { get; set; }
    public virtual string Name { get; set; }
}

DbContext

public class Context : DbContext {
    public DbSet<Thing> Things { get; set; }
    public DbSet<Option1> Option1s { get; set; }
    public DbSet<Option2> Option2s { get; set; }
    public DbSet<Option3> Option3s { get; set; }

    public ObjectContext ObjectContext {
        get { return ((IObjectContextAdapter)this).ObjectContext; }
    }

    protected override void OnModelCreating(DbModelBuilder modelBuilder) {
        base.OnModelCreating(modelBuilder);
    }
}

Seed()

var option1s = new List<Option1> {
    new Option1{Name="Red"},
    new Option1{Name="Green"}};
    option1s.ForEach(x => db.Option1s.Add(x));
    db.SaveChanges();
var option2s = new List<Option2> {
    new Option2{Name = "Tall"},
    new Option2{Name = "Short"}};
    option2s.ForEach(x => db.Option2s.Add(x));
    db.SaveChanges();
var option3s = new List<Option3> {
    new Option3{Name = "Male"},
    new Option3{Name = "Female"}};
    option3s.ForEach(x => db.Option3s.Add(x));
    db.SaveChanges();

var thing = db.Things.Create();
    thing.Option1 = db.Option1s.Find(1); //the first thing.XXXX shows null no matter what order
    thing.Option2 = db.Option2s.Find(1); //but the FK's work for all three of them
    thing.Option3 = db.Option3s.Find(1);
db.Things.Add(thing);
db.SaveChanges();

回答1:

Wow. I don't know what you did there, but you made the object state tracker very angry.

EDIT:

I believe this to be some sort of bug in the debugger and the way it works with dynamic proxies. I say this because you can do Console.WriteLine(thing.Option1.Id); and it will give you the correct id. If you get rid of the dynamic proxy by saying var thing = new Thing();, the debugger problem goes away.

Here is the more standard way to do what you're trying to do.

    var option1s = new List<Option1> {
            new Option1{Name="Red"},
            new Option1{Name="Green"}};
    option1s.ForEach(x => db.Option1s.Add(x));

    var option2s = new List<Option2> {
            new Option2{Name = "Tall"},
            new Option2{Name = "Short"}};
    option2s.ForEach(x => db.Option2s.Add(x));

    var option3s = new List<Option3> {
            new Option3{Name = "Male"},
            new Option3{Name = "Female"}};
    option3s.ForEach(x => db.Option3s.Add(x));

    var thing = db.Things.Create();
    thing.Option1 = option1s[0];
    thing.Option2 = option2s[0];
    thing.Option3 = option3s[0];

    db.Things.Add(thing);
    db.SaveChanges();

来源：https://stackoverflow.com/questions/6783484/proxys-first-navigation-property-is-null-when-seeding-ef-4-1

标签

entity-framework

entity-framework-4.1