c# - 在 Entity Framework 中的抽象类上配置自动增量字段

Question

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

但我无法使自动递增 ID 正常工作或正确配置。

我已经试过了:

modelBuilder.Entity<Animal>().Property(_ => _.ID)
    .HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);

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

我也尝试在 Dog 实体上做同样的事情，它正确地将标识属性添加到 Animals 表中的 ID 列，但我得到一个 UpdateException 当我尝试在 SaveChanges() 方法上向数据库添加新实体时:

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

如何正确设置抽象类型的ID列自动递增，并使其在添加数据时起作用？

Answer 1

我会说使用接口(interface)或单独的抽象类来放置像这样的通用功能:

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; }
}