使用实体框架4代码优先（POCO）如何声明一对一的关系 [英] How to declare one to one relationship using Entity Framework 4 Code First (POCO)

问题描述

如何使用Entity Framework 4 Code First（POCO）声明一对一的关系？

How to declare a one to one relationship using Entity Framework 4 Code First (POCO)?

我发现这个问题（实体框架4中的一对一关系），但是文章答案引用不是有用的（有一行代码是1-1关系，但没有提到如何定义它）。

I found this question (one-to-one relationships in Entity Framework 4) , but the article that the answer references was not useful (there is one line of code that is a 1-1 relationship, but no mention of how to define it).

推荐答案

你是否只是寻找这样的东西？

Are you just looking for something like this?

public class User
{
    public int Id { get; set; }
    public string Username { get; set; }
    public Profile Profile { get; set; }
    public int ProfileId { get; set; }
}

public class Profile
{
    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string PostalCode { get; set; }
    // etc...
}

public class UserMapping : EntityConfiguration<User>
{
    public UserMapping()
    {
        this.HasKey(u => u.Id);
        this.Property(u => u.Username).HasMaxLength(32);

        // User has ONE profile.
        this.HasRequired(u => u.Profile);
    }
}

public class ProfileMapping : EntityConfiguration<Profile>
{
    public ProfileMapping()
    {
        this.HasKey(p => p.Id);
        this.Property(p => p.FirstName).HasMaxLength(32);
        this.Property(p => p.LastName).HasMaxLength(32);
        this.Property(p => p.PostalCode).HasMaxLength(6);
    }
}

编辑：是的，在我面前没有VS，但是您需要在 UserMapping 中添加以下行，而不是当前的 HasRequired 并添加一个 ProfileId 属性（而不是您添加的 Profile_Id ）：

EDIT: Yeah I didn't have VS in front of me but you need to add the following line in the UserMapping instead of the current HasRequired and also add a ProfileId property (instead of Profile_Id that you added):

this.HasRequired(u => u.Profile).HasConstraint((u, p) => u.ProfileId == p.Id);

我目前不认为有办法解决这个问题，但我相信会改变因为我们只在CTP4。如果我可以这样说，这将是很好：

I currently don't think there's a way around this, but I'm sure it'll change since we're only in CTP4. It'd be nice if I could say:

this.HasRequired(u => u.Profile).WithSingle().Map(
    new StoreForeignKeyName("ProfileId"));

这样我不需要包含一个 ProfileId 属性。也许现在有一种方法，还有一个是清晨，我想想：）

This way I wouldn't have to include a ProfileId property. Maybe there is a way around this currently and it's still to early in the morning for me to think :).

还记得调用。 （资料）如果您要包含导航属性。

Also remember to call .Include("Profile") if you want to include a "navigational property".

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