EF Code First多对多不工作 [英] EF Code First Many-to-Many not working
问题描述
使用实体框架代码第一范式我将以下对象和关系定义为ASP.Net MVC3应用程序的一部分。问题是照片和画廊对象之间的多对多关系无法正常工作。
Using the Entity Framework Code First paradigm I have defined the following objects and relationships as part of an ASP.Net MVC3 application. The problem is the many-to-many relationship between the Photo and Gallery objects is not working properly.
目前,一个画廊可以包含许多照片 - 这是正确的。但照片只能与一个画廊相关联 - 这是不正确的。我想要一张照片能够在许多画廊。如果我在照片已经与另一个图库相关联时将照片添加到图库,那么它将从其他图库中删除。
Currently a gallery can contain many photos - this is correct. But a photo can only be associated with one Gallery - this is incorrect. I want a photo to be able to be in many galleries. If I add a photo to a gallery when it is already associated with another gallery, it is removed from the other gallery.
我非常感谢您的解决方案如何使这种多对多关系工作。
I would very much appreciate your solutions on how to make this many-to-many relationship work.
这是我的代码:
public class Photo
{
public int ID { get; set; }
public string Title { get; set; }
public virtual ICollection<Gallery> Galleries { get; set; }
}
public class Gallery
{
public int ID { get; set; }
public string Title { get; set; }
public virtual ICollection<Photo> Photos { get; set; }
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
/* I would expect the following to cause a lookup table to
* be created but it isnt */
modelBuilder.Entity<Photo>().HasMany<Gallery>(p => p.Galleries);
modelBuilder.Entity<Gallery>().HasMany<Photo>(g => g.Photos);
}
我在自己的自定义数据库初始化程序中使用以下代码。 >
I am using the following code within my own custom database initializer.
public void InitializeDatabase(PhotoDBContext context)
{
var dbCreationScript = ((IObjectContextAdapter)context).ObjectContext.CreateDatabaseScript();
Log(dbCreationScript);
context.Database.ExecuteSqlCommand(dbCreationScript);
}
通过记录dbCreationScript变量,我可以看到生成的相关sql这些表如下。
By logging the dbCreationScript variable I can see that the relevant sql that is generated for these tables is as follows.
create table [dbo].[Galleries] (
[ID] [int] not null identity,
[Title] [nvarchar](max) null,
[Photo_ID] [int] null,
primary key ([ID])
);
create table [dbo].[Photos] (
[ID] [int] not null identity,
[Title] [nvarchar](max) null,
[Gallery_ID] [int] null,
primary key ([ID])
);
alter table [dbo].[Photos] add constraint [Gallery_Photos] foreign key ([Gallery_ID]) references [dbo].[Galleries]([ID]);
alter table [dbo].[Galleries] add constraint [Photo_Galleries] foreign key ([Photo_ID]) references [dbo].[Photos]([ID]);
正如你所看到的,没有生成SQL生成查找表,这可能是为什么关系是不工作 - 为什么没有创建一个查找表?
As you can see there is no SQL generated to create a lookup table which is probably why the relationship is not working - why isnt a lookup table being created?
推荐答案
我相信你需要使用这样的东西:
I believe you need to use something like this:
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Photo>()
.HasMany<Gallery>(x => x.Galleries)
.WithMany(x => x.Photos)
.Map(x =>
{
x.MapLeftKey("ID");
x.MapRightKey("ID");
x.ToTable("GalleryPhotos");
});
}
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