实体框架入口负载相关实体

Question

Let's say I have the following auto generated entities

public class Entity1
{
    public int Id { get; set; }
    public int Entity2Id { get; set; }
    public Entity2 { get; set; }
}

public class Entity2
{
    public int Id { get; set; }
}

I have an update method in my MVC application that looks like this:

public ActionResult Edit(Entity1 entity)
{
    _db.Entry(entity).State = EntityState.Modified;
    _db.SaveChanges();
    DoSomething(entity);
}

Currently entity has the Entity2Id property set, but not the Entity2 property set. How can I hydrate all related entities in the entity object.

I've tried doing

_db.Find(entity.ID)

If I put that method right after calling SaveChanges it retrieves the cached entity which doesn't have Entity2 hydrated. If I put it before the Entry call, I get an error on the Entry call saying that an Entry already exists. I've also tried calling Reload on the entry, which doesn't seem to do anything.

Answer 1

You need to have Entity2 as virtual :

public virtual Entity2 { get; set; }

EF will auto hydrate that for you.

And if you happen to change the Entity2Id and want to reload the changed entity, you can do so explicitly by saying:

context.Entry(entity).Reference(p => p.Entity2).Load();