Entity Framwork one to one problem-白红宇

问题：

//针对“一对一”关系的设置

modelBuilder.Entity<BlogSite>().HasRequired(b => b.BlogUser).

WithRequiredDependent().Map(conf => conf.MapKey("UserID"));

//出现如下恶心的脚本

SELECT

[Extent1].[BlogID] AS [BlogID],

[Extent1].[BlogApp] AS [BlogApp],

[Extent1].[IsActive] AS [IsActive],

[Join1].[UserID1] AS [UserID],

[Join1].[Author] AS [Author],

[Join3].[BlogID] AS [BlogID1]

FROM [dbo].[BlogSite] AS [Extent1]

LEFT OUTER JOIN (SELECT [Extent2].[UserID] AS [UserID1], [Extent2].[Author] AS [Author]

FROM [dbo].[BlogUser] AS [Extent2]

LEFT OUTER JOIN [dbo].[BlogSite] AS [Extent3] ON [Extent2].[UserID] = [Extent3].[UserID] ) AS [Join1]

ON [Extent1].[UserID] = [Join1].[UserID1]

LEFT OUTER JOIN (SELECT [Extent4].[UserID] AS [UserID2], [Extent5].[BlogID] AS [BlogID]

FROM [dbo].[BlogUser] AS [Extent4]

LEFT OUTER JOIN [dbo].[BlogSite] AS [Extent5]

ON [Extent4].[UserID] = [Extent5].[UserID] ) AS [Join3] ON [Extent1].[UserID] = [Join3].[UserID2]

WHERE 1 = [Extent1].[IsActive]

dudu的解决办法：

WithMany()

dudu的解决方案无疑可以满足大家的需求，但是看着这个很难跟一对一联系起来，不过话说回来，在一对多中也是这个脚本。其实一对一本质是就是把概念上一张表在物理上分为两张表。

网上看了一句话：

For one-to-one relationships, EF expects that the tables are using the same primary key. And really, if it's a true one-to-one they probably should.

说的真好，但是实际上大家在设计库，不管什么原因总有跟设计原则相违背的地方，我们不可能重新设计表等恐怖的操作。在dudu的示例中BlogSite和BlogUser 共有字段UserId，那么咱就在Ef中指定如下

modelBuilder.Entity
    
     ().ToTable("BlogUser"); modelBuilder.Entity
     
      ().HasKey(u => u.UserID); modelBuilder.Entity
      
       ().ToTable("BlogSite"); modelBuilder.Entity
       
        ().HasKey(b => b.);

一对一：

modelBuilder.Entity
    
     ().HasRequired(b => b.BlogUser). WithRequiredDependent();

输出脚本：

SELECT

[Extent1].[BlogID] AS [BlogID],

[Extent1].[BlogApp] AS [BlogApp],

[Extent1].[IsActive] AS [IsActive],

[Extent1].[UserID] AS [UserID],

[Extent2].[UserID] AS [UserID1],

[Extent2].[Author] AS [Author]

FROM [dbo].[BlogSite] AS [Extent1]

INNER JOIN [dbo].[BlogUser] AS [Extent2] ON [Extent1].[UserID] = [Extent2].[UserID]

WHERE 1 = [Extent1].[IsActive]

本文转自today4king博客园博客，原文链接：http://www.cnblogs.com/jinzhao/archive/2011/07/14/2106196.html，如需转载请自行联系原作者