Entity Framework Core 5：配置多对多关系，如何指定外键名称

Question

我有一个现有的 SQL Server 数据库，其中通过连接表实现了多对多关系Books<-> ：AuthorsPublications

CREATE TABLE [dbo].[Books]
(
    [BookId] INT IDENTITY,
    [Title] NVARCHAR(160) NOT NULL,
    ...
)

CREATE TABLE [dbo].[Authors]
(
    [AuthorId] INT IDENTITY,
    ...
)

CREATE TABLE [dbo].[Publications]
(
    [BookId] INT NOT NULL,
    [AuthorId] INT NOT NULL,

    CONSTRAINT [PK_Publication] PRIMARY KEY ([BookId], [AuthorId])
)

我需要在 Entity Framework Core 5 中配置多对多关系。

对于 EF 6，这相当简单：

protected override void OnModelCreating(DbModelBuilder mb)
{
    mb.Entity<Author>() // an Author
         .HasMany(a => a.Books) // has many Books
         .WithMany(b => b.Authors) // with many Authors
         .Map(mc =>
               {
                    mc.ToTable("Publications"); // Join table: Publications
                    mc.MapLeftKey("AuthorId"); // FK Author: AuthorId
                    mc.MapRightKey("BookId"); // FK Book : BookId
               });
}

但我在使用 Entity Framework Core 5 时遇到问题：

protected override void OnModelCreating(ModelBuilder mb)
{
    mb.Entity<Author>() // an Author
          .HasMany(a => a.Books) // has many Books
          .WithMany(b => b.Authors) // with many Authors
          .UsingEntity(j => j.ToTable("Publications")); // join table: Publications
          // how to define foreign key columns?
}

我不知道如何映射外键列。EF Core 5 使用模式AuthorsAuthorId和BooksBookId。

如何更改此命名约定？

谢谢

Answer 1

如果多对多表在 C# 代码中不相关，您可以尝试此操作：

public class Author
{
   public int AuthorId { get; set; }
   public ICollection<Book> Books { get; set; }
}
public class Book
{
   public int BookId { get; set; }
   public ICollection<Author> Authors { get; set; }
}
public class Db : DbContext
{
   protected override void OnModelCreating(ModelBuilder mb)
   {
      mb.Entity<Author>() // an Author
      .HasMany(a => a.Books) // has many Books
      .WithMany(b => b.Authors) // with many Authors
      .UsingEntity<Dictionary<string, object>>("Publications",
        x => x.HasOne<Book>().WithMany().HasForeignKey(nameof(Book.BookId)),
        y => y.HasOne<Author>().WithMany().HasForeignKey(nameof(Author.AuthorId)),
        z => z.ToTable("Publications"));
   }
}