EntityFramwork 核心和继承 TPT

Question

I have read some posts, like this , this and this .

Some tables from the database:

I migrated from EF4 creating the models using Scaffold-DbContext , I expected it generates followings:

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

instead I got:

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

I read that TPC is not supported in EFCore yet, but this is TPT, right?

However, if I modify the generated models, I get:

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.'

Is it possible to modify the models or is there something in the DB that forces this pattern?

Answer 1

Table-per-Type isn't supported in EF Core versions lower than 5.0. It was first added in EF Core 5 Preview 8 . If you want to use TPT you'll have to migrate to EF Core 5.

Currently EF Core 5 is in RC2 which can be used in production. From the announcement :

This is a feature complete release candidate of EF Core 5.0 and ships with a "go live" license. You are supported using it in production.

From the documentation's example, these classes :

[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; }
}

Will be mapped to these tables:

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
);