实体框架6代码第一种方法 - 唯一约束不起作用 [英] Entity Framework 6 Code First approach - unique constraint doesn't work

问题描述

我正在使用EF 6与代码第一种方法。除了在数据库级别的数据库约束检查之外，我想在POCO级别提供唯一的约束检查。我遵循文章使用流畅的API设置唯一约束有人建议使用[Index（）]属性。

这是我的代码：我已经在我的poco类中应用了相同的，但是看起来仍然是数据库级别的异常。 / p>

  [Key] 
 public decimal OrderId {get;组; } 
 
 [Index（ORDER_CC，2，IsUnique = true）] 
 public decimal？ MemberId {get;组; } 
 
 [Index（ORDER_CC，3，IsUnique = true）] 
 public decimal？ ItemId {get;组; } 
 
 [Index（ORDER_CC，1，IsUnique = true）] 
 public decimal？ OrderNumber {get;组; } 
 
 public decimal？成本{get;组; } 
 
 public DateTime Time {get;组; 
  

我不知道我在这里做错什么？

我也想要问：

1. 我需要保持相同的索引我的数据库表中有一个名称作为订单？


2. 我如何知道它是否通过EF约束检查或数据库约束检查得到验证？




$ b

这是我在POCO类中的索引的顺序与数据库中的Order表中定义的索引相同。数据库脚本：

  CREATE UNIQUE INDEX xyz.ORDER_CC ON xyz.Order 
（OrderNumber ，MemberId，ItemId）
 LOGGING 
 TABLESPACE USERS 
 PCTFREE 10 
 INITRANS 2 
 MAXTRANS 255 
 STORAGE（
 INITIAL 128K 
 NEXT 1M 
 MINEXTENTS 1 
 MAXEXTENTS无限
 PCTINCREASE 0 
 BUFFER_POOL DEFAULT 
 FLASH_CACHE DEFAULT 
 CELL_FLASH_CACHE DEFAULT 
）
 NOPARALLEL; 
  

任何想法？

解决方案

该问题不在Index属性中，它符合您的期望。





索引属性不验证一个唯一的约束，它仅指示实体框架首先在迁移期间在数据库中创建一个索引。从您的问题，您很清楚，您使用EF代码优先，即POCO和编码映射，但您可以使用预先存在的数据库。在这种情况下，应用索引属性是无用的。





这样也可以在数据库中回答你的问题：检查约束。这就是为什么它仍然抛出错误。如果你想在代码中有一个独特的限制，你必须自己写。




I am using EF 6 with code first approach. In addition to database constraints check at database level, I would like to provide unique constraints check at POCO level. I have followed article Setting unique Constraint with fluent API? where someone suggested to use [Index()] attribute. I have applied the same in my poco class but looks like it is still throwing an exception from Database level.

Here is my code:

[Key]
public decimal OrderId { get; set; }

[Index("ORDER_CC", 2, IsUnique = true)]
public decimal? MemberId { get; set; }

[Index("ORDER_CC", 3, IsUnique = true)]
public decimal? ItemId { get; set; }

[Index("ORDER_CC", 1, IsUnique = true)]
public decimal? OrderNumber { get; set; }

public decimal? Cost { get; set; }

public DateTime Time { get; set; }

I am not sure what I am doing wrong here?

I also want to ask followings:

1. Do I need to keep the same index name as the one I have on my database table for Order?
2. How do I know, it is getting validate against EF constraints check or Database constraints check?
3. I have kept the same order for index on POCO class compare to one defined in Order table in database.

Here is my Database script:

CREATE UNIQUE INDEX xyz.ORDER_CC ON xyz.Order
(OrderNumber, MemberId, ItemId)
LOGGING
TABLESPACE USERS
PCTFREE    10
INITRANS   2
MAXTRANS   255
STORAGE    (
            INITIAL          128K
            NEXT             1M
            MINEXTENTS       1
            MAXEXTENTS       UNLIMITED
            PCTINCREASE      0
            BUFFER_POOL      DEFAULT
            FLASH_CACHE      DEFAULT
            CELL_FLASH_CACHE DEFAULT
           )
NOPARALLEL;

Any idea?

解决方案

The problem is not in the Index attribute, it's in your expectations of what it does.

The Index attribute doesn't validate a unique constraint, it only instructs Entity Framework code-first to create an index in the database during a migration. From your questions it is clear that you use EF code-first, i.e. POCO's and coded mappings, but you work with a preexisting database. In this case, applying index attributes is useless.

So that also answers your question where the constraint is checked: in the database. And that's why it's still throwing errors. If you want a unique constraint in code you'll have to write it yourself.

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