Entity Framework Code First not lazy loading after save

Question

I have a lookup table and a data table in my db. I'll use gender and person for an example. So let's say the gender table looks like so:

Id         Code
1          Male
2          Female

and the person table looks like so:

Id         Name             GenderId
1          Bob              1
2          Jane             2

I've modelled both tables in EF code first like so:

public class Gender
{
    public int Id {get;set;}
    public string Code {get;set;}
}

public class Person
{
    public int Id {get;set;}
    public string Name {get;set;}
    public int GenderId {get;set;}

    public virtual Gender {get;set;}
}

If I read a person already in the DB then I can access person.Gender.Code without a problem. If I do this:

var person = new Person
             {
                 Name = "Bob",
                 GenderId = 1,
             };

context.People.Add(person);
context.SaveChanges();

var code = person.Gender.Code;

Then it will save correctly but will fail on the last line as gender is null. If I then open a new context and load the saved entity then the last line works fine. Is there a way that I can access gender directly after a save as if I just loaded the entity from the DB?

Sorry about that, it didn't save the first time and when I came back to the page it must not have loaded the whole thing. — VARAK
– VARAK, Commented Jun 14, 2012 at 6:35

nemesv · Accepted Answer · 2012-06-14 07:15:13Z

11

Your problem is that when you use new Person() it will just create a POCO object which doesn't know how to get the it's Gender property. So to make the lazy loading work you need proxies.

You can create your person as a proxy with DbSet.Create():

var person = context.People.Create();
person.Name = "Bob";
person.GenderId = 1;

context.People.Add(person);
context.SaveChanges();

edited Jun 14, 2012 at 7:15

answered Jun 14, 2012 at 6:36

nemesv

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5 Comments

VARAK Over a year ago

Thank you!! The first piece of code worked great. The second one would have been preferable but it did not work. It seems that it just spits out the cached version of the person which doesn't have lazy loading enabled.

nemesv Over a year ago

Yeah it seems Find() won't return a proxy... Can you try it with context.People.Single(p => p.Id == person.Id) ?

nemesv Over a year ago

Single also doesn't work. However if you call context.People.Load(); before the Find or Single it works, but it reloads the collection into the context.So I think you should use the Create to generate proxies so I removed the Find related part of my answer.

VARAK Over a year ago

It does the same thing. Straight out the cache and not a proxy.

VARAK Over a year ago

Awesome! I'll use the .Create(). Thanks a lot!

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