实体框架code首先不能懒加载后保存 [英] Entity Framework Code First not lazy loading after save
问题描述
我有一个查找表,在我的数据库的数据表。我将利用性别和人的例子。所以我们可以说男女表看起来像这样:
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
和人表看起来像这样:
Id Name GenderId
1 Bob 1
2 Jane 2
我第一次像这样建模两个表中的EF code:
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;}
}
如果我在数据库中读出一个人已经那么我可以访问person.Gender。没有问题code。如果我这样做:
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;
然后,它会正确保存,但会失败在最后一行性别为空。如果我再打开一个新的上下文并加载保存的实体,那么最后一行正常工作。有没有办法,我可以直接访问后,男女的方式保存,如果我只是加载从DB?
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?
推荐答案
您的问题是,当你使用新的Person()
它只是创建一个POCO对象,没有按知道如何得到它的性别
属性。因此,为了使您需要的延迟加载工作<一href="http://blogs.msdn.com/b/adonet/archive/2011/02/02/using-dbcontext-in-ef-feature-ctp5-part-8-working-with-proxies.aspx">proxies.
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.
您可以创建你的人与 DbSet.Create代理( ):
var person = context.People.Create();
person.Name = "Bob";
person.GenderId = 1;
context.People.Add(person);
context.SaveChanges();
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