C#外键无法将对象添加到对象列表

Question

我有 2 个模型类电影和客户。我制作了一对多外键，以便可以将电影添加到客户列表中。但现在我无法向客户添加电影，也没有出现任何错误。

这是我的代码。

电影课

public class Movie
{
    [Key]
    public int MovieId { get; set; }
    public String Name { get; set; }

    [Column(TypeName = "datetime2")]
    public DateTime? DateCreated { get; set; }

    public int? CustomerId { get; set; }
    public Customer Customer { get; set; }
}

客户类别

public class Customer
{
    [Key]
    public int CustomerId { get; set; }
    public string Name { get; set; }
    public string LastName { get; set; }
    public bool IsCreated { get; set; }
    public int MaxMovies { get; set; }

    [Column(TypeName = "datetime2")]
    public DateTime Created { get; set; }

    [Column(TypeName = "datetime2")]
    public DateTime? LastEdited { get; set; }

    [ForeignKey("MovieId")]
    public List<Movie> Movies = new List<Movie>();
}

这是我的CustomerController 类中的代码，应该将电影添加到我的客户

[HttpGet]
public IActionResult AddMovie(int id)
{
    List<Movie> movieList = new List<Movie>();
    movieList = dbContext.Movies.ToList();

    AddMovieViewModel viewModel = new AddMovieViewModel()
    {
        movies = movieList,
        customer = dbContext.Customers
           .Where(s => s.CustomerId == id)
           .FirstOrDefault()
    };

    return View(viewModel);
}

[HttpPost]
public IActionResult AddMovie (int id,int cid)
{
    Customer customer = dbContext.Customers
        .Where(s => s.CustomerId == cid)
        .FirstOrDefault();
    Movie movie = dbContext.Movies
        .Where(s => s.MovieId == id)
        .FirstOrDefault();
    movie.CustomerId = customer.CustomerId;
    customer.Movies.Add(movie);

    dbContext.SaveChanges();
    return RedirectToAction("Index");
}

我希望有人能告诉我我的代码有什么问题。

Answer 1

我相信这是您正在寻找的模型结构

客户

public class Customer
{

    [Key]
    public int CustomerId { get; set; }

    public string Name { get; set; }
    public string LastName { get; set; }
    public bool IsCreated { get; set; }
    public int MaxMovies { get; set; }

    [Column(TypeName = "datetime2")]
    public DateTime Created { get; set; }

    [Column(TypeName = "datetime2")]
    public DateTime? LastEdited { get; set; }

    public ICollection<Movie> Movies = new List<Movie>();

}

电影

public class Movie
{

    [Key]
    public int MovieId { get; set; }

    public String Name { get; set; }

    [Column(TypeName = "datetime2")]
    public DateTime? DateCreated { get; set; }

    [ForeignKey("Customer")]
    public int? CustomerId { get; set; }

    public Customer Customer { get; set; }

}

然后在创建/编辑电影时，只需为电影分配一个 CustomerId，然后您就可以通过访问 Customer.Movies 检索客户的电影

Answer 2

您不是在创建新的Movie，而是在搜索现有的电影。所以创建新电影并分配CustomerId：

Customer customer = dbContext.Customers
    .Where(s => s.CustomerId == cid)
    .FirstOrDefault();
Movie movie = new Movie();
movie.CustomerId = customer.CustomerId;
movie.Name = "My new movie";
movie.DateCreated = DateTime.Now;

dbContext.Customers.Add(customer);
dbContext.Movies.Add(movie);

dbContext.SaveChanges();

EntityFramework 将插入一个新实体。