如何型号N - N的关系在EF code首先自动生成的视图可以正常工作？

问题描述

我用EF $ C C首先$并在NN关系的问题，假设我们有一个唱一些流派的歌手，所以我们需要这款车型：艺术家，流派和ArtistsGenres，我定义模型如下：

I use EF Code First and have a problem in n-n relationship, assume we have a singer that sing in some genres, so we need this models: Artist, Genre, and ArtistsGenres, I define Models as following:

这是我的艺人型号：

public class Artist
{
    public long Id { get; set; }
    public string Name { get; set; }
    public ICollection<Genre> Genres { get; set; }
}

和我的类型型号：

public class Genre
{
    public long Id { get; set; }
    public string Title { get; set; }
    public ICollection<Artist> Artists { get; set; }
}

和我的上下文类：

public class MusicDB : DbContex
{
    public DbSet<Artist> Artists { get; set; }
    public DbSet<Genre> Genres { get; set; }
    public DbSet<ArtistsGenres> ArtistsGenres { get; set; }

protected override void OnModelCreating(DbModelBuilder modelBuilder) {
modelBuilder.Entity<Artist>()
            .HasMany(a => a.Genres)
            .WithMany(g => g.Artists)
            .Map(model => {
                model.ToTable("ArtistsGenres");
                model.MapLeftKey("Artist_Id");
                model.MapRightKey("Genre_Id");
            });

        base.OnModelCreating(modelBuilder);
        }
}

但没有艺术家和流派在MVC自动生成视图之间无任何关系。

But there is not any relationship between Artists and Genres when MVC generate views automatically.

例如，我需要改变一个艺术家的流派在编辑看来，在创建视图我可以设置流派的艺术家，或在索引视图我想展示流派每个艺术家。但是，没有任何一代的有关艺术家的时候MVC自动生成的意见流派。

For example, I need to change Genres of an Artist in edit view, in Create view I can set Genres for an Artist, or in Index View I want show genres for each Artist. But there isn't any generation for Genres in relation to Artist when MVC generate views automatically.

我知道我可以从两侧同时访问的流派和艺术家，但我感兴趣的MVC中自动生成的观点，因为我们希望：为前：每个艺人演出相关的流派

I know I can access both Genres and Artists from both side but I am interesting in MVC automatically generate views as we want: for ex: for each artist show related Genres.

我怎样才能做到这一点？是我的模型是否正确？这是适用于任何（N至N）的关系，需要对ICollection的两侧？或者我需要的上下文类的 OnModelCreating压倒一切的一些元素的方法，例如是这样的：

How can I do this? Is my model correct? Is this true for any (n to n) relation that needs ICollection on both side? Or do I need some elements in overriding of OnModelCreating method in context class, for example something like this:

modelBuilder.Entity<Artist>()
    .HasMany(a => a.Genres)
    .WithMany(g => g.Artists);

请帮帮我，我不知道NTON关系的真正实现。

Please help me, I don't know the exact implementation of NtoN relationship.

推荐答案

您还没有创建一个单独的型号在一个多于─之间的关联模型一对多的关系。真正的 ArtistsGenres 是没有必要的。因此，删除它，你只需要改变你的模型构建器来这样一句：

You haven't to create a separate Model for association between to models in a many-to-many relationship. Really the ArtistsGenres is not necessary. So, remove it, and you just have to change your modelBuilder to this one:

modelBuilder.Entity<Artist>()
    .HasMany(c => c.Genres)
    .WithMany(x => x.Artists)
    .Map(a => {
        a.ToTable("ArtistsGenres");
        a.MapLeftKey("ArtistId");
        a.MapRightKey("GenreId");
    });

这将使用 ArtistsGenres 表映射一个多到多艺术家之间的关系表流派表自动。

It will use the ArtistsGenres table to map a many-to-many relationship between Artists table andGenres table automatically.

注意：当你定义的 ArtistsGenres 模式，EF不会把它视为一种关系，因为你告诉他的嘿EF，我还有一个名为model ArtistsGenres ！请管理它给我！的

Note: When you define the ArtistsGenres model, EF will not look at it as a relationship,because you tell him that Hey EF, I have another model named ArtistsGenres! Please manage it for me!!!

您的新实体和的DbContext将是这些：

public class Artist {
    public long Id { get; set; }
    public string Name { get; set; }
    public ICollection<Genre> Genres { get; set; }
}

public class Genre {
    public long Id { get; set; }
    public string Title { get; set; }
    public ICollection<Artist> Artists { get; set; }
}

public class MusicDB : DbContex {

    public DbSet<Artist> Artists { get; set; }
    public DbSet<Genre> Genres { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder) {
    modelBuilder.Entity<Artist>()
        .HasMany(c => c.Genres)
        .WithMany(x => x.Artists)
        .Map(a => {
            a.ToTable("ArtistsGenres");
            a.MapLeftKey("ArtistId");
            a.MapRightKey("GenreId");
        });

}

让我知道，如果您有任何疑问或需要任何部分澄清。

Let me know if you have any questions or need clarifications on any part.

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