我在.NET 4.5的控制台应用程序使用实体框架5.0.0.0和我有它两个表来访问数据库,象这样它们之间的外键关系:实体框架5.0复合外键非主键 - 是否有可能?
奇数关于它的一点是,外键在B(Almost1, Almost2)
和A(Almost1, Almost2)
之间,而不是从B(AId)
到A(AId)
。这是由SQL服务器允许的,因为Almost1
和Almost2
组合是唯一的,都不可为空(至少在表A
上 - 它们是B
它们是因为它是可选关系,但是是由)。
下面是一些SQL创建这样的情况:
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])
的事情是,它似乎没有被实体框架允许的 - 这样的话还是我只是没有正确定义我的模型?
这里是我的C#:
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();
}
}
}
它抛出一个InvalidOperationException
说:
指定的关联外键列 'Almost1,差不多有' 无效。指定的列数必须与主键列的数量匹配。
如果我忽略了AId
列,而是让Almost1
和Almost2
复合主键,所以我OnModelCreating
方法现在看起来是这样的:
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"));
}
它的工作原理,但我真的不希望这样做,因为还有一个表(我们称之为C
),它与A
以传统方式相关,具有AId
列和外键从C.AId
到A.AId
。
是的,这有点奇怪我知道 - 但是有可能在Entity Framework中处理这个问题吗?
实体框架不支持唯一键,如果没有这些键,不幸的是它不能建模您的外键。 – hvd
@hvd :-(好的,谢谢 – kmp