[英]Entity Framework Code First unique index foreign key throws DbUpdate Exception
Here's the entites and context code: 这是实体和上下文代码:
public class Family
{
public int FamilyID { get; set; }
public String address { get; set; }
public virtual ICollection<Member> FamilyMembers { get; set; }
}
public class Member
{
[Index("MemberUniqueID", IsUnique = true)]
public int MemberID { get; set; }
[StringLength(50)] [Index("MemberUniqueIndex", 1, IsUnique = true)]
public String name { get; set; }
[StringLength(50)] [Index("MemberUniqueIndex", 2, IsUnique = true)]
public String surname { get; set; }
public int age { get; set; }
public int FamilyID { get; set; }
public virtual Family Family { get; set; }
}
public class Bicycle
{
public int BicycleID { get; set; }
public virtual Member Owner { get; set; }
}
public class MyContext : DbContext
{
public MyContext : base () { }
public DbSet<Member> MemberDB { get; set; }
public DbSet<Family> FamilyDB { get; set; }
public DbSet<Bicycle> BicycleDB { get; set; }
}
Now, I add a few examples of each, add them and SaveChanges();
现在,我为每个示例添加一些示例,并添加它们和
SaveChanges();
. 。 Then I try to run this code:
然后,我尝试运行以下代码:
public void bicycle_set_FK(int IDbicycle, int IDmember)
{
var bicycleToFind = BicycleDB.Find(IDbicycle);
var memberToSetAsFK = MemberDB.Find(IDmember);
bicycleToFind.Owner = memberToSetAsFK;
SaveChanges();
}
And as a result, I get this error: 结果,我得到这个错误:
An unhandled exception of type 'System.Data.Entity.Infrastructure.DbUpdateException' occurred in EntityFramework.dll Cannot insert duplicate key row in object 'dbo.Members' with unique index 'MemberUniqueIndex'.
EntityFramework.dll中发生了类型为'System.Data.Entity.Infrastructure.DbUpdateException'的未处理异常。无法在具有唯一索引'MemberUniqueIndex'的对象'dbo.Members'中插入重复的键行。 The duplicate key value is (John, Smith).
重复的键值为(John,Smith)。 The statement has been terminated.
该语句已终止。
The weird thing is, if I run that method simultaneously while adding the examples, the method works fine and sets the FK as expected. 奇怪的是,如果我在添加示例的同时运行该方法,则该方法可以正常工作并按预期设置FK。 But if I first add the examples with the first run of the code, and I try to set FKs on the second run of the code, it throws that exception.
但是,如果我首先在代码的第一次运行中添加示例,然后尝试在代码的第二次运行中设置FK,则会抛出该异常。
Okay, so I've done as recommended and after reading the artice you linked I have this: 好的,所以我已经按照建议完成了,在阅读了您链接的文章后,我得到了:
[ForeignKey("MemberID")]
public int? OwnerID { get; set; }
public virtual Member MemberID { get; set; }
And the method looks like this: 该方法如下所示:
public void bicycle_set_FK(int IDbicycle, int IDmember)
{
var bicycleToFind = BicycleDB.Find(IDbicycle);
bicycleToFind.MemberID = null;
bicycleToFind.OwnerID = IDmember;
SaveChanges();
}
But this generates a new problem: 但这产生了一个新问题:
"Violation of PRIMARY KEY constraint 'PK_dbo.Members'. Cannot insert duplicate key in object 'dbo.Members'. The duplicate key value is (0).\\r\\nThe statement has been terminated."
“违反了PRIMARY KEY约束'PK_dbo.Members'。无法在对象'dbo.Members'中插入重复键。重复键值为(0)。\\ r \\ n该语句已终止。“
The values I use are 1 and 3 ( bicycle_set_FK(1, 3);
). 我使用的值是1和3(
bicycle_set_FK(1, 3);
)。 Members contain 3 rows with IDs: 1, 2 and 3. So where does it find that zero, since it's not in the database nor do I enter it at any point in the code? 成员包含ID为1、2和3的3行。那么,该零在哪里找到,因为它不在数据库中,所以我也不能在代码的任何位置输入它。
And one more thing: the article doesn't mention how to solve that problem in a one-to-many relationship. 还有一件事:本文没有提到如何以一对多关系解决该问题。 How do I add FK between Family and Member?
如何在家庭和会员之间添加FK? Do I add some property such as
public List<Member> FamilyMembersFK
? 是否添加一些属性,例如
public List<Member> FamilyMembersFK
?
Entity framework is re-adding your Owner(Member). 实体框架正在重新添加您的Owner(成员)。 There are a couple of ways around this, but since you have the FK try this:
有两种方法可以解决此问题,但是既然您有FK,请尝试以下操作:
public class Bicycle
{
public int BicycleID { get; set; }
public int MemberID { get; set; } // You can call this ownerId, but then you need to setup the relationship with annotation or fluent
public virtual Member Owner { get; set; }
}
public void bicycle_set_FK(int IDbicycle, int IDmember)
{
var bicycleToFind = BicycleDB.Find(IDbicycle);
// var memberToSetAsFK = MemberDB.Find(IDmember); ** Don't need to do this since you have FK **
bicycleToFind.MemberId = IDmember;
SaveChanges();
}
See https://msdn.microsoft.com/en-us/magazine/dn166926.aspx?f=255&MSPPError=-2147217396 参见https://msdn.microsoft.com/zh-cn/magazine/dn166926.aspx?f=255&MSPPError=-2147217396
EDIT: First, I highly recommend you follow some convention when naming your navigation classes and keys. 编辑:首先,我强烈建议您在命名导航类和键时遵循一些约定。 You are calling your navigation class "MemberId" - that is very confusing.
您正在将导航类称为“ MemberId”-这非常令人困惑。 If you want the FK to be OwnerId, go with something like this:
如果您希望FK成为OwnerId,请执行以下操作:
public int? OwnerID { get; set; }
[ForeignKey("OwnerID")]
public virtual Member Owner { get; set; }
Second, you don't need this annotation: 其次,您不需要此注释:
//[Index("MemberUniqueID", IsUnique = true)] **MemberID will be a identity key by default so it will have a unique index created.
public int MemberID { get; set; }
Now you can insert an existing owner like this: 现在,您可以像这样插入现有所有者:
public void bicycle_set_FK(int IDbicycle, int IDmember)
{
var bicycleToFind = BicycleDB.Find(IDbicycle);
bicycleToFind.OwnerID = IDmember; // Don't worry about the nav class, just set the FK
SaveChanges();
}
Regarding the one to many, you already have that configured with: 关于一对多,您已经配置了:
public virtual ICollection<Member> FamilyMembers { get; set; }
So to add a new member: 因此要添加一个新成员:
var newMember = new Member {
Name = "Joe",
Surname = "Smith",
Age = 30,
FamilyId = familyId
};
context.Members.Add(newMember);
SaveChanges();
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