Question

我有一些类似于这些代码的第一个实体：

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...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)
)

数据看起来像这样：

---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);

但是因为Animal是抽象的，所以似乎没有在表上设置IDENTITY(1,1)属性。

我也试过在Dog实体上做同样的事情，它正确地将身份属性添加到Animals表中的ID列，但是当我获得UpdateException时尝试在SaveChanges()方法上向数据库添加新实体：

A dependent property in a ReferentialConstraint is mapped to a store-generated column. Column: 'ID'.

如何正确地将抽象类型上的ID列设置为自动递增，并在添加数据时使其工作？

Answer 1

我想说使用接口或单独的抽象类来放置这样的常用功能：

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; }
}

Answer 2

使用这些模型......

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

你应该得到：

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)

这是你想要的，对吧？

参考： Inheritance with EF Code First: Part 2 – Table per Type (TPT)

请注意，如果最初创建的字段没有标识，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

Answer 3

我遇到了同样的问题，我在抽象类中使用数据注释修复它，如下所示：

public abstract class Animal {
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int ID { get; set; }
    public int NumberOfLegs { get; set; }
}

在实体框架

3 个答案: