C# 实体框架5.0复合外键到非主键-可能吗?
我在.net 4.5控制台应用程序中使用Entity Framework 5.0.0.0,我必须访问包含两个表的数据库,其中两个表之间存在外键关系,如下所示: 奇怪的是,外键位于C# 实体框架5.0复合外键到非主键-可能吗?,c#,.net,entity-framework-5,poco,C#,.net,Entity Framework 5,Poco,我在.net 4.5控制台应用程序中使用Entity Framework 5.0.0.0,我必须访问包含两个表的数据库,其中两个表之间存在外键关系,如下所示: 奇怪的是,外键位于B(Almost1,Almost2)和A(Almost1,Almost2)之间,而不是从B(AId)到A(AId)。SQL server允许这样做,因为Almost1和Almost2的组合是唯一的,并且两者都不可为空(至少在表A上-在B上,它们是可选关系,但这是由by决定的) 下面是一些创建这种情况的SQL: CREA
B(Almost1,Almost2)
和A(Almost1,Almost2)
之间,而不是从B(AId)
到A(AId)
。SQL server允许这样做,因为Almost1
和Almost2
的组合是唯一的,并且两者都不可为空(至少在表A
上-在B
上,它们是可选关系,但这是由by决定的)
下面是一些创建这种情况的SQL:
CREATE TABLE [dbo].[A](
[AId] [int] IDENTITY(1,1) NOT NULL,
[Almost1] [int] NOT NULL,
[Almost2] [int] NOT NULL,
CONSTRAINT [PK_A] PRIMARY KEY CLUSTERED
(
[AId] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY],
CONSTRAINT [A_Constraint] UNIQUE NONCLUSTERED
(
[Almost1] ASC,
[Almost2] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
CREATE TABLE [dbo].[B](
[BId] [int] IDENTITY(1,1) NOT NULL,
[Almost1] [int] NULL,
[Almost2] [int] NULL,
CONSTRAINT [PK_B] PRIMARY KEY CLUSTERED
(
[BId] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
ALTER TABLE [dbo].[B] ADD CONSTRAINT [FK_A_B] FOREIGN KEY([Almost1], [Almost2])
REFERENCES [dbo].[A] ([Almost1], [Almost2])
问题是,实体框架似乎不允许这样做——是这样还是我没有正确定义模型
这是我的简历:
它可以工作,但我并不真的想这样做,因为还有一个表(我们称之为C
)以传统方式与a
相关,它有一个AId
列,外键从C.AId
转到a.AId
是的,我知道这有点奇怪-但有可能在实体框架中处理这个问题吗?如前所述,因为EF不支持唯一键和其他SQL对象。我最终创建了一些脚本作为嵌入式资源,并让它们作为drop/create初始值设定项的种子过程的一部分执行
不确定这是否允许您在代码中的对象之间导航,但在一个过程中更新数据库效果很好。Entity Framework不支持唯一键,不幸的是,如果没有唯一键,它就无法为您的外键建模。
public class MyContext : DbContext
{
public MyContext(string connectionString) : base(connectionString)
{
MyAs = Set<A>();
MyBs = Set<B>();
}
public DbSet<A> MyAs { get; private set; }
public DbSet<B> MyBs { get; private set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
var aEntity = modelBuilder.Entity<A>();
aEntity.ToTable("A");
aEntity.HasKey(a => a.AId);
var bEntity = modelBuilder.Entity<B>();
bEntity.ToTable("B");
bEntity.HasKey(a => a.BId);
bEntity
.HasOptional(b => b.A)
.WithMany(a => a.Bs)
.Map(m => m.MapKey("Almost1", "Almost2"));
}
}
public class A
{
public int AId { get; set; }
public int Almost1 { get; set; }
public int Almost2 { get; set; }
public virtual ICollection<B> Bs { get; private set; }
public void AddB(B b)
{
if (b == null) throw new ArgumentNullException("b");
if (Bs == null) Bs = new List<B>();
if (!Bs.Contains(b)) Bs.Add(b);
b.A = this;
}
}
public class B
{
public int BId { get; set; }
public virtual A A { get; set; }
}
class Program
{
static void Main()
{
using (var ctx = new MyContext(@"connection string"))
{
ctx.MyAs.Add(new A { Almost1 = 1, Almost2 = 1 });
ctx.SaveChanges();
}
}
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
var aEntity = modelBuilder.Entity<A>();
aEntity.ToTable("A");
aEntity.HasKey(a => new { a.Almost1, a.Almost2 });
aEntity.Ignore(a => a.AId);
var bEntity = modelBuilder.Entity<B>();
bEntity.ToTable("B");
bEntity.HasKey(a => a.BId);
bEntity
.HasOptional(b => b.A)
.WithMany(a => a.Bs)
.Map(m => m.MapKey("Almost1", "Almost2"));
}