在 EF4 Code First 中创建多对多关系

Question

我正在使用 EF4 Code-First 进行建模的 ASP.NET MVC 项目。我有以下模型类：

public class ComicBook
{
    public long ComicBookID { get; set; }
    public string IssueTitle { get; set; }
    public int IssueNumber { get; set; }
    public DateTime PublishDate { get; set; }

    public IList<ComicBookPerson> Writers { get; set; }
    public IList<ComicBookPerson> Pencillers { get; set; }

    public IList<User> CollectingUsers { get; set; }
}

public class ComicBookPerson
{
    public long ComicBookPersonID { get; set; }
    public string Name { get; set; }

    public IList<ComicBook> WorkedOnComicBooks { get; set; }
}

public class User
{
    [Key]
    public long UserID { get; set; }
    public string Email { get; set; }

    public IList<ComicBook> CollectedBooks { get; set; }
}

还有以下 DbContext：

public class ComicContext : DbContext
{
    public DbSet<ComicBook> ComicBooks { get; set; }
    public DbSet<ComicBookPerson> ComicBookPerson { get; set; }
    public DbSet<User> Users { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<ComicBook>()
            .HasMany(b => b.Writers)
            .WithMany(w => w.WorkedOnComicBooks)
            .Map(t => t.MapLeftKey("ComicBookID")
                .MapRightKey("WriterID")
                .ToTable("ComicBook_Writers"));

        modelBuilder.Entity<ComicBook>()
            .HasMany(b => b.Pencillers)
            .WithMany(p => p.WorkedOnComicBooks)
            .Map(t => t.MapLeftKey("ComicBookID")
                .MapRightKey("PencillerID")
                .ToTable("ComicBook_Penciller"));
    }
}

需要应用的规则是：

• 用户的收藏中可以有许多漫画书
• 漫画书可以在许多用户的收藏中
• 每本 ComicBook 可以有 1 个或多个作者
• 每本 ComicBook 可以有 1 个或多个 Pencillers
• ComicBookPerson 可以是任何书籍的作家或铅笔手
• ComicBookPerson 可以在许多书籍上工作，作为作家、铅笔手，或两者兼而有之

用户和漫画书之间的多对多模式创建得很好。打破的是 ComicBooks 和 ComicBookPersons 之间的多对多。我得到的错误信息是：

Schema specified is not valid. Errors: 
(15,6) : error 0040: Type ComicBook_Writers is not defined in namespace Comics.Models (Alias=Self).

我基本上想要两个连接表，一个叫做 ComicBook_Writers，一个叫做 ComicBookPencillers。两个表都将包含一个 ComicBookID 和一个 ComicBookPersonID。这在 EF Code First 中可行吗？

Answer 1

ComicBookPerson 类中需要两个与作家和铅笔工相关的集合属性。

public class ComicBookPerson
{
    public long ComicBookPersonID { get; set; }
    public string Name { get; set; }

    public IList<ComicBook> WroteComicBooks { get; set; }
    public IList<ComicBook> PenciledComicBooks { get; set; }
}

模型映射为

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Entity<ComicBook>()
        .HasMany(b => b.Writers)
        .WithMany(w => w.WroteComicBooks)
        .Map(t => t.MapLeftKey("ComicBookID")
            .MapRightKey("WriterID")
            .ToTable("ComicBook_Writers"));

    modelBuilder.Entity<ComicBook>()
        .HasMany(b => b.Pencillers)
        .WithMany(p => p.PenciledComicBooks)
        .Map(t => t.MapLeftKey("ComicBookID")
            .MapRightKey("PencillerID")
            .ToTable("ComicBook_Penciller"));
}

Answer 2

我认为这个模型接近正确，但仍然缺少一些东西。
ComicBookPerson 既可以是作家也可以是铅笔人，这意味着您仍然需要在班级中添加第三个列表ComicBookPerson：

public IList<ComicBook> WroteComicBooks { get; set; }
public IList<ComicBook> PenciledComicBooks { get; set; }
public IList<ComicBook> WrotPencComicBooks { get; set; }

我说的对吗？