Entity framework 实体框架核心：在WebAPI中包含多对多相关对象

我对.NET框架不太熟悉，但决定试用ASP.NET核心和EF核心。我想制作一个非常简单的Web API后端，但我在处理多对多关系时遇到了问题

我知道我需要为这两个实体创建一个关系表，如本文中的示例所示：

我还让我的模型生成器按照这里的描述创建关系

我的代码如下所示：

在DBContext中：

protected override void OnModelCreating(ModelBuilder builder)
    {
        base.OnModelCreating(builder);

        builder.Entity<MovieActor>().HasKey(x => new { x.MovieId, x.ActorId});

        builder.Entity<MovieActor>()
            .HasOne(m => m.Movie)
            .WithMany(ma => ma.MovieActors)
            .HasForeignKey(m => m.MovieId);

        builder.Entity<MovieActor>()
            .HasOne(m => m.Actor)
            .WithMany(ma => ma.MovieActors)
            .HasForeignKey(a => a.ActorId);

    }

    public DbSet<Movie> Movies { get; set; }

    public DbSet<Actor> Actors { get; set; }


}

---

您必须按如下所示进行更改

型号：

namespace Test.Models
{
    public class Movie
    {
        public int MovieId { get; set; }
        public string Title { get; set; }
        public DateTime ReleaseDate { get; set; }
        public string Code { get; set; }
        public string Path { get; set; }

        public ICollection<MovieActor> MovieActors { get; set; }
    }

    public class Actor
    {
        public int ActorId { get; set; }
        public string Name { get; set; }
        public ICollection<MovieActor> MovieActors { get; set; }
    }

    public class MovieActor
    {
        public int MovieId { get; set; }
        public Movie Movie { get; set; }

        public int ActorId { get; set; }
        public Actor Actor { get; set; }
    }
}

protected override void OnModelCreating(ModelBuilder builder)
    {
        base.OnModelCreating(builder);

        builder.Entity<MovieActor>().HasKey(x => new { x.MovieId, x.ActorId});

        builder.Entity<MovieActor>()
            .HasOne(m => m.Movie)
            .WithMany(ma => ma.MovieActors)
            .HasForeignKey(m => m.MovieId);

        builder.Entity<MovieActor>()
            .HasOne(m => m.Actor)
            .WithMany(ma => ma.MovieActors)
            .HasForeignKey(a => a.ActorId);

    }

    public DbSet<Movie> Movies { get; set; }

    public DbSet<Actor> Actors { get; set; }

    public DbSet<MovieActor> MovieActors { get; set; }

 }

var actor = new Actor { ... };
context.Actors.Add(actor);

var movie = new Movie { ... };
context.Movies.Add(movie);

var movieActor = new MovieActor { Actor = actor , Movie = movie };
context.MovieActors.Add(movieActor);

context.SaveChanges();

如何添加记录：

namespace Test.Models
{
    public class Movie
    {
        public int MovieId { get; set; }
        public string Title { get; set; }
        public DateTime ReleaseDate { get; set; }
        public string Code { get; set; }
        public string Path { get; set; }

        public ICollection<MovieActor> MovieActors { get; set; }
    }

    public class Actor
    {
        public int ActorId { get; set; }
        public string Name { get; set; }
        public ICollection<MovieActor> MovieActors { get; set; }
    }

    public class MovieActor
    {
        public int MovieId { get; set; }
        public Movie Movie { get; set; }

        public int ActorId { get; set; }
        public Actor Actor { get; set; }
    }
}

protected override void OnModelCreating(ModelBuilder builder)
    {
        base.OnModelCreating(builder);

        builder.Entity<MovieActor>().HasKey(x => new { x.MovieId, x.ActorId});

        builder.Entity<MovieActor>()
            .HasOne(m => m.Movie)
            .WithMany(ma => ma.MovieActors)
            .HasForeignKey(m => m.MovieId);

        builder.Entity<MovieActor>()
            .HasOne(m => m.Actor)
            .WithMany(ma => ma.MovieActors)
            .HasForeignKey(a => a.ActorId);

    }

    public DbSet<Movie> Movies { get; set; }

    public DbSet<Actor> Actors { get; set; }

    public DbSet<MovieActor> MovieActors { get; set; }

 }

var actor = new Actor { ... };
context.Actors.Add(actor);

var movie = new Movie { ... };
context.Movies.Add(movie);

var movieActor = new MovieActor { Actor = actor , Movie = movie };
context.MovieActors.Add(movieActor);

context.SaveChanges();

---

我已经做了这些更改，但现在我的控制器不高兴了。我无法再创建新的MovieActor实体并将其添加到上下文中，它表示，

“DbContext”不包含“MovieActor”的定义。

。我如何在这里添加关系？我现在创建了一部新电影，然后创建了一个新演员，然后用这些对象创建了一个电影演员实体。当然，我刚刚从控制器中添加了一个示例方法。尝试找到演员并将其添加到相应电影中的演员列表中。似乎您尚未实现我提到的更改。这样我们无法找到解决方案。因为如果您看到

EF core

文档，它们也显示了与我的帖子相同的方式。如果您无法根据这一点进行更改，希望您没有解决此问题的方法。例如：

\u context.Movie.FirstOrDefault（m=>m.code==Moviebundle.Movie.code）

。这必须是这样的

\u context.Movies.FirstOrDefault（m=>m.code==Moviebundle.Movie.code）

。还有很多其他人。。。