Question

我阅读了一些帖子，例如this，this和this。

数据库中的某些表：

我从使用Scaffold-DbContext创建模型的EF4迁移过来，我希望它会生成以下内容：

class Tagesinkassos {}
class TagesinkassosPOSTagesinkasso : Tagesinkassos {}
class TagesinkassosTagesinkasso : Tagesinkassos {}

相反，我得到了：

class TagesinkassosPOSTagesinkasso {}
class TagesinkassosTagesinkasso {}
class Tagesinkassos {
    public virtual TagesinkassosPOSTagesinkasso TagesinkassosPOSTagesinkasso { get; set; }
    public virtual TagesinkassosTagesinkasso TagesinkassosTagesinkasso { get; set; }
}

我读到EFCore还不支持TPC，但这是TPT，对吧？

但是，如果我修改生成的模型，则会得到：

System.InvalidOperationException: 'The entity type 'TagesinkassosTagesinkasso' cannot be mapped to a table because it is derived from 'Tagesinkassos'. Only base entity types can be mapped to a table.'

是否可以修改模型，或者数据库中是否有某种强制这种模式的东西？

Answer 1

低于5.0的EF Core版本不支持

Table-per-Type。它首先添加到EF Core 5 Preview 8中。如果要使用TPT，则必须迁移到EF Core 5。

当前，EF Core 5位于RC2中，可用于生产。来自announcement：

这是EF Core 5.0的功能齐全的候选版本，并附带“上线”许可证。支持在生产中使用它。

在文档的示例中，这些类：

[Table("Animals")]
public class Animal
{
    public int Id { get; set; }
    public string Species { get; set; }
}

[Table("Pets")]
public class Pet : Animal
{
    public string Name { get; set; }
}

[Table("Cats")]
public class Cat : Pet
{
    public string EdcuationLevel { get; set; }
}

[Table("Dogs")]
public class Dog : Pet
{
    public string FavoriteToy { get; set; }
}

将被映射到这些表：

CREATE TABLE [Animals] (
    [Id] int NOT NULL IDENTITY,
    [Species] nvarchar(max) NULL,
    CONSTRAINT [PK_Animals] PRIMARY KEY ([Id])
);

CREATE TABLE [Pets] (
    [Id] int NOT NULL,
    [Name] nvarchar(max) NULL,
    CONSTRAINT [PK_Pets] PRIMARY KEY ([Id]),
    CONSTRAINT [FK_Pets_Animals_Id] FOREIGN KEY ([Id]) 
               REFERENCES [Animals] ([Id]) ON DELETE NO ACTION
);

CREATE TABLE [Cats] (
    [Id] int NOT NULL,
    [EdcuationLevel] nvarchar(max) NULL,
    CONSTRAINT [PK_Cats] PRIMARY KEY ([Id]),
    CONSTRAINT [FK_Cats_Animals_Id] FOREIGN KEY ([Id]) 
               REFERENCES [Animals] ([Id]) 
               ON DELETE NO ACTION,
    CONSTRAINT [FK_Cats_Pets_Id] FOREIGN KEY ([Id]) 
               REFERENCES [Pets] ([Id]) 
               ON DELETE NO ACTION
);

CREATE TABLE [Dogs] (
    [Id] int NOT NULL,
    [FavoriteToy] nvarchar(max) NULL,
    CONSTRAINT [PK_Dogs] PRIMARY KEY ([Id]),
    CONSTRAINT [FK_Dogs_Animals_Id] FOREIGN KEY ([Id]) 
               REFERENCES [Animals] ([Id]) 
               ON DELETE NO ACTION,
    CONSTRAINT [FK_Dogs_Pets_Id] FOREIGN KEY ([Id]) 
               REFERENCES [Pets] ([Id]) 
               ON DELETE NO ACTION
);

EntityFramwork核心和继承TPT

1 个答案: