在实体框架中的抽象类上配置“自动增量”字段
本文关键字:自动增量 字段 配置 框架 实体 抽象类 | 更新日期: 2023-09-27 18:32:15
我有一些类似于这些的代码优先实体:
public abstract class Animal {
public int ID { get; set; }
public int NumberOfLegs { get; set; }
}
public class Dog : Animal {
public string OtherDogRelatedStuff { get; set; }
}
public class Bird : Animal {
public string OtherBirdRelatedStuff { get; set; }
}
public class MyContext : DbContext {
public IDbSet<Animal> Animals { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder) {
var pluraliser = PluralizationService.CreateService(new System.Globalization.CultureInfo("en-GB"));
modelBuilder.HasDefaultSchema("vs");
modelBuilder.Types().Configure(t => t.ToTable(pluraliser.Pluralize(t.ClrType.Name)));
// This next line doesn't give ID column IDENTITY(1,1)
modelBuilder.Entity<Animal>().Property(_ => _.ID).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
// This line puts IDENTITY(1,1) on Animal.ID, but causes errors when I try to add/update data.
//modelBuilder.Entity<Dog>().Property(_ => _.ID).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
base.OnModelCreating(modelBuilder);
}
}
我想要每种类型的表格...所以表格看起来像这样:
CREATE TABLE Animals (
ID INT NOT NULL IDENTITY(1,1),
NumberOfLegs INT NOT NULL,
CONSTRAINT pkAnimals PRIMARY KEY (ID)
)
CREATE TABLE Dogs (
ID INT NOT NULL,
OtherDogRelatedStuff VARCHAR(200),
CONSTRAINT pkDogs PRIMARY KEY (ID),
CONSTRAINT fkAnimal_Dog FOREIGN KEY (ID) REFERENCES Animals(ID)
)
CREATE TABLE Birds (
ID INT NOT NULL,
OtherBirdRelatedStuff VARCHAR(200),
CONSTRAINT pkBirds PRIMARY KEY (ID),
CONSTRAINT fkAnimal_Bird FOREIGN KEY (ID) REFERENCES Animals(ID)
)
数据如下所示:
---Animals----------
ID NumberOfLegs
1 4
2 4
3 2
---Dogs---------------------
ID OtherDogRelatedStuff
1 Woof1
2 Woof2
---Birds---------------------
ID OtherCatRelatedStuff
3 Sqwark1
但是我无法使自动增量ID正常工作或正确配置。
我试过这个:
modelBuilder.Entity<Animal>().Property(_ => _.ID)
.HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
但是由于Animal
是抽象的,这似乎并没有在表上设置IDENTITY(1,1)
属性。
我也尝试对Dog
实体执行相同的操作,这会将 identity 属性正确添加到 Animals
表中的 ID 列,但是当我尝试在 SaveChanges()
方法上向数据库中添加新实体时,我得到了一个UpdateException
:
A dependent property in a ReferentialConstraint is mapped to a store-generated column. Column: 'ID'.
如何才能将抽象类型的ID列正确设置为自动递增,并在添加数据时使其正常工作?
我会说使用接口或单独的抽象类来放置像这样的常见功能:
public interface Common{
int ID { get; set; }
}
public class Animal : Common {
[DatabaseGenerated(System.ComponentModel.DataAnnotations.Schema.DatabaseGeneratedOption.Identity)]
public int ID { get; set; }
public int NumberOfLegs { get; set; }
}
public class Dog : Common {
public int ID { get; set; }
public string OtherDogRelatedStuff { get; set; }
}
有了这些模型...
public abstract class Animal
{
public int ID { get; set; }
public int NumberOfLegs { get; set; }
}
public class Dog : Animal
{
public string OtherDogRelatedStuff { get; set; }
}
public class Bird : Animal
{
public string OtherBirdRelatedStuff { get; set; }
}
。这在上下文中...
public IDbSet<Animal> Animals { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Entity<Dog>().ToTable("Dogs");
modelBuilder.Entity<Bird>().ToTable("Birds");
}
。然后在包管理器中执行Add-Migration "Animals"
然后Update-Database -Script
您应该获得:
CREATE TABLE [dbo].[Animals] (
[ID] [int] NOT NULL IDENTITY,
[NumberOfLegs] [int] NOT NULL,
CONSTRAINT [PK_dbo.Animals] PRIMARY KEY ([ID])
)
CREATE TABLE [dbo].[Dogs] (
[ID] [int] NOT NULL,
[OtherDogRelatedStuff] [nvarchar](max),
CONSTRAINT [PK_dbo.Dogs] PRIMARY KEY ([ID])
)
CREATE INDEX [IX_ID] ON [dbo].[Dogs]([ID])
CREATE TABLE [dbo].[Birds] (
[ID] [int] NOT NULL,
[OtherBirdRelatedStuff] [nvarchar](max),
CONSTRAINT [PK_dbo.Birds] PRIMARY KEY ([ID])
)
CREATE INDEX [IX_ID] ON [dbo].[Birds]([ID])
ALTER TABLE [dbo].[Dogs]
ADD CONSTRAINT [FK_dbo.Dogs_dbo.Animals_ID] FOREIGN KEY ([ID])
REFERENCES [dbo].[Animals] ([ID])
ALTER TABLE [dbo].[Birds]
ADD CONSTRAINT [FK_dbo.Birds_dbo.Animals_ID] FOREIGN KEY ([ID])
REFERENCES [dbo].[Animals] ([ID])
INSERT [dbo].[__MigrationHistory]([MigrationId], [ContextKey], [Model], [ProductVersion])
VALUES (N'etc)
这就是你想要的,对吧?
参考:EF 代码优先继承:第 2 部分 – 每个类型的表 (TPT)
请注意,如果最初创建字段时没有标识,则有时可能会遇到使用标识创建的字段的问题(反之亦然)。您可以通过删除并重新创建表来解决此问题:https://stackoverflow.com/a/18917348/150342
我遇到了同样的问题,我在抽象类中使用数据注释修复了它,如下所示:
public abstract class Animal {
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int ID { get; set; }
public int NumberOfLegs { get; set; }
}