[使用$ C C第一的DbContext $实体框架5.0 RC 的]

public class Compositon
{

    public string Id { get; set; }

    public string SimpletonId { get; set; }

    [ForeignKey("SimpletonId")]
    public Simpleton Simpleton { get; set; }

    public string CompanitonId { get; set; }

    [ForeignKey("CompanitonId")]
    public Companiton Companiton { get; set; }
}

第一关 - SaveChanges的以空数据库工程

var composition = new Compositon();
compositon.Id = "UniquePrimaryKey";
var simpleton = new Simpleton();
// This foreign key does not exist in database yet
simpleton.Id = "Simpleton1";
composition.Simpleton = simpleton;
var companiton = new Companiton();
companiton.Id = "SomeOther1";
composition.Companiton = companiton;
// Repositor references the DbContext
Repositor.Compositons.Add(composition);
Repositor.SaveChanges();

第二遍 - 现有的儿童外键信息到家长故障

var composition = new Compositon();
compositon.Id = "AnotherUniquePrimaryKey";
var simpleton = new Simpleton();
// This foreign key already exists in database
simpleton.Id = "Simpleton1";
composition.Simpleton = simpleton;
var companiton = new Companiton();
companiton.Id = "SomeOther2";
composition.Companiton = companiton;
Repositor.Compositons.Add(composition);
Repositor.SaveChanges();

DbUpdateException：更新条目时发生错误

我需要能够保存这些父类到数据库中，因为它们是独一无二的，即使他们有时包含已存储的导航性能 - ？我怎么能救母从此子主键冲突

推荐答案

在第二遍，你将需要检索现有的心眼从的DbContext 。我猜，你能做到这一点是这样的：

In the second pass you will need to retrieve the existing Simpleton from the DbContext. I'm guessing that you could do that like this:

`simpleton = Repositor.Simpletons.First(s => s.Id == "Simpleton1");`

目前，您要创建一个全新的，它的实体框架试图插入这样，因此键冲突。

Currently, you're creating a brand new one, which the Entity Framework tries to insert as such, hence the key violation.