如何將記錄插入到 EF Core 中的聯接表中

Question

我首先是 Entity Framework Core 代碼的新手（使用 EF Core 6.07）。 我正在嘗試將一條記錄插入到具有兩列的連接表中，但我收到“InvalidOperationException：嘗試保存更改時'MovieGenre.MovieId'的值未知”的錯誤。這是因為該屬性也是關系中的主要實體未知的外鍵。” 連接表如下：

    public class MovieGenre
    {
        [Required(ErrorMessage = "Movie Id required")]
        public int MovieId { get; set; }
        public Movies Movies { get; set; }

        [Required(ErrorMessage = "Genre Id required")]
        public int GenreId { get; set; }
        public Genre Genre { get; set; }
    }

它的兩列引用下表的 ID 列：

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

        [Required(ErrorMessage = "Title cannot be Null")]
        [Column(TypeName = "nvarchar(256)")]
        public string Title { get; set; }

        [Column(TypeName = "nvarchar(MAX)")]
        public string Overview { get; set; }

        [Column(TypeName = "nvarchar(512)")]
        public string Tagline { get; set; }

        [Column(TypeName = "decimal(18,2)")]
        public decimal Budget { get; set; }

        [Column(TypeName = "decimal(18,2)")]
        public decimal Revenue { get; set; }

        [Column(TypeName = "nvarchar(2084)")]
        public string ImdbUrl { get; set; }

        [Column(TypeName = "nvarchar(2084)")]
        public string TmdbUrl { get; set; }

        [Column(TypeName = "nvarchar(2084)")]
        public string PosterUrl { get; set; }

        [Column(TypeName = "nvarchar(2084)")]
        public string BackdropUrl { get; set; }

        [Column(TypeName = "nvarchar(64)")]
        public string OriginalLanguage { get; set; }

        [Column(TypeName = "datetime2(7)")]

        public DateTime ReleaseDate { get; set; }

        public int RunTime { get; set; }

        [Column(TypeName = "decimal(5,2)")]
        public decimal Price { get; set; }

        [Column(TypeName = "datetime2(7)")]
        public DateTime CreatedDate { get; set; }

        [Column(TypeName = "datetime2(7)")]
        public DateTime UpdatedDate { get; set; }

        [Column(TypeName = "nvarchar(MAX)")]
        public string UpdatedBy { get; set; }

        [Column(TypeName = "nvarchar(MAX)")]
        public string CreatedBy { get; set; }
        
        public List<MovieCrew> MovieCrews { get; set; }

        public List<MovieCast> MovieCasts { get; set; }

        public List<MovieGenre> MovieGenres { get; set; }

        public List<Trailer> Trailers { get; set; }

        public List<Favorite> Favorites { get; set; }

        public List<Purchase> Purchases { get; set; }

        public List<Review> Reviews { get; set; }
    }

    public class Genre
    {
        [Key]
        public int GenreId { get; set; }

        [Required(ErrorMessage = "Name cannot be null")]
        [Column(TypeName = "nvarchar(64)")]
        public string Name { get; set; }

        public List<MovieGenre> MovieGenres { get; set; }
    }

我還設置了我的自定義數據庫上下文文件來手動指定兩個主表和連接表之間的外鍵關系。 另外，我在連接表中添加了兩個外鍵列作為復合主鍵。

protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Movies>()
                .HasMany(x => x.MovieGenres).WithOne(x => x.Movies).HasForeignKey(x => x.MovieId);
            modelBuilder.Entity<Genre>()
                .HasMany(x => x.MovieGenres).WithOne(x => x.Genre).HasForeignKey(x => x.GenreId);

            modelBuilder.Entity<MovieGenre>()
                .HasKey(o => new { o.MovieId, o.GenreId });
        }

我正在嘗試使用 model、controller 和視圖將數據插入連接表。 我能夠成功地插入到 Movies 和 Genre 表中，但是當我嘗試為連接表 MovieGenre 執行此操作時，我收到了上面粗體提到的錯誤。 我嘗試插入連接表的 MovieID 和 GenreID 已經存在於 Movie 和 Genre 表中。 有人可以幫我了解我做錯了什么嗎？

編輯：添加我用來插入交叉引用表的代碼。

IRepositoryAsync：

using System;
namespace Antra.Movie.Core.Contracts.Repositories
{
    public interface IRepositoryAsync<T> where T: class
    {
        Task<int> InsertAsync(T Entity);
        Task<int> UpdateAsync(T Entity);
        Task<T> GetByIdAsync(int id);
        Task<int> DeleteAsync(int id);
        Task<IEnumerable<T>> GetAllAsync();
    }
}

IMovieGenreRepositoryAsync：

using System;
using Antra.Movie.Core.Entities;
namespace Antra.Movie.Core.Contracts.Repositories
{
    public interface IMovieGenreRepositoryAsync:IRepositoryAsync<MovieGenre>
    {
    }
}

BaseRepositoryAsync：

using System;
using Antra.Movie.Core.Contracts.Repositories;
using Antra.Movie.Infrastructure.Data;
using Microsoft.EntityFrameworkCore;

namespace Antra.Movie.Infrastructure.Repositories
{
    public class BaseRepositoryAsync<T>:IRepositoryAsync<T> where T: class
    {

        MovieDbContext db;

        public BaseRepositoryAsync(MovieDbContext _context)
        {
            db = _context;
        }

        public async Task<int> DeleteAsync(int id)
        {
            var entity = await db.Set<T>().FindAsync(id);
            db.Set<T>().Remove(entity);
            return await db.SaveChangesAsync();

        }

        public async Task<IEnumerable<T>> GetAllAsync()
        {
            return await db.Set<T>().ToListAsync();
        }

        public async Task<T> GetByIdAsync(int id)
        {
            var entity = await db.Set<T>().FindAsync(id);
            return entity;
        }

        public async Task<int> InsertAsync(T Entity)
        {
            await db.Set<T>().AddAsync(Entity);
            return await db.SaveChangesAsync();

        }

        public async Task<int> UpdateAsync(T Entity)
        {
            db.Entry<T>(Entity).State = EntityState.Modified;
            return await db.SaveChangesAsync();
        }
    }
}

MovieGenreRepositoryAsync：

using System;
using Antra.Movie.Core.Contracts.Repositories;
using Antra.Movie.Core.Entities;
using Antra.Movie.Infrastructure.Data;

namespace Antra.Movie.Infrastructure.Repositories
{
    public class MovieGenreRepositoryAsync : BaseRepositoryAsync<MovieGenre>, IMovieGenreRepositoryAsync
    {
        public MovieGenreRepositoryAsync(MovieDbContext _context):base(_context)
        {
        }
    }
}

IMovieGenreServiceAsync：

using System;
using Antra.Movie.Core.Model;

namespace Antra.Movie.Infrastructure.Services
{
    public interface IMovieGenreServiceAsync
    {
        Task<int> InsertMovieGenre(MovieGenreModel _movieGenreModel);
    }
}

電影流派服務異步：

using System;
using Antra.Movie.Core.Contracts.Repositories;
using Antra.Movie.Core.Entities;
using Antra.Movie.Core.Model;

namespace Antra.Movie.Infrastructure.Services
{
    public class MovieGenreServiceAsync:IMovieGenreServiceAsync
    {
        IMovieGenreRepositoryAsync MovieGenreRepo;
        public MovieGenreServiceAsync(IMovieGenreRepositoryAsync _movieGenreRepo)
        {
            MovieGenreRepo = _movieGenreRepo;
        }

        public async Task<int> InsertMovieGenre(MovieGenreModel _movieGenreModel)
        {
            MovieGenre moviegenreentity = new MovieGenre()
            {
                MovieId = _movieGenreModel.MovieId,
                GenreId = _movieGenreModel.GenreId
            };
            return await MovieGenreRepo.InsertAsync(moviegenreentity);
        }
    }
}

電影流派型號：

using System;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using Antra.Movie.Core.Entities;

namespace Antra.Movie.Core.Model
{
    public class MovieGenreModel
    {
        [Required(ErrorMessage = "Movie Id required")]
        public int MovieId { get; set; }
        public Movies Movies { get; set; }

        [Required(ErrorMessage = "Genre Id required")]
        public int GenreId { get; set; }
        public Genre Genre { get; set; }

        public MovieGenreModel()
        {
        }
    }
}

電影流派控制器：

using System;
using Antra.Movie.Core.Model;
using Antra.Movie.Infrastructure.Services;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Rendering;

namespace Antra.Movie.WebMVC.Controllers
{
    public class MovieGenreController:Controller
    {
        IGenreServiceAsync genreServiceAsync;
        IMovieServiceAsync movieServiceAsync;
        IMovieGenreServiceAsync movieGenreServiceAsync;
        public MovieGenreController(IGenreServiceAsync _genreService, IMovieServiceAsync _movieService, IMovieGenreServiceAsync _moviegenreService)
        {
            genreServiceAsync = _genreService;
            movieServiceAsync = _movieService;
            movieGenreServiceAsync = _moviegenreService;
        }
        public async Task<IActionResult> Index()
        {
            ViewBag.GenreSelect = new SelectList(await genreServiceAsync.GetAllGenres(), "Id", "Name");

            return View();
        }
        [HttpGet]
        public IActionResult Create()
        {
            return View();
        }
        [HttpPost]
        public async Task<IActionResult> Create(MovieGenreModel _model)
        {
            if (ModelState.IsValid)
            {
                await movieGenreServiceAsync.InsertMovieGenre(_model);
            }
            return View(_model);
        }
    }
}

為 MovieGenreController 創建.cshtml 視圖：

@addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers
@model GenreModel
<form method="post" asp-controller="MovieGenre" asp-action="Create">
    <div class="form-group">
        <label for="GenreName">GenreId</label>
        <input type="text" name="Name" class="form-control" id="GenreName" placeholder="Enter genre name">
        <span asp-validation-for="Name"></span>
    </div>
    <div class="form-group">
        <label for="GenreName">MovieId</label>
        <input type="text" name="Name" class="form-control" id="GenreName" placeholder="Enter genre name">
        <span asp-validation-for="Name"></span>
    </div>
    <button type="submit" class="btn btn-primary">Save</button>
</form>

Answer 1

首先，除非您沒有任何特定屬性，否則您不需要將映射表作為MovieGenre 。 此外，如果您首先使用代碼，則無需在DbContext中執行任何操作，映射和您需要的所有內容都將自動創建，除了DbSets 。 所以我會推薦：

在上下文中

public virtual DbSet<Movie> Movies { get; set; }
public virtual DbSet<Genre> Genres { get; set; }

電影

public class Movie
{
   public Movie()
   {
       this.Genres = new HashSet<Genre>();
   }

    public int Id { get; set; }

    // Other Props....

    public virtual ICollection<Genre> Genres { get; set; }
}

流派

public class Genre
{
    public Genre()
    {
        this.Movies = new HashSet<Movie>();
    }

    public int Id { get; set; }

    //Other Props....

    public virtual ICollection<Movie> Movies { get; set; }
}

無需添加分隔符，

var genre = new Genre { Name = "Action" };
var movie = new Movie { Name = "MovieName" };
movie.Genres.Add(genre);

await context.AddAsync(movie);
await context.SaveChangesAsync();

詢問

//by movie name
var moviesByName = db.Movies.Include(x => x.Genres).Where(x => x.Name = "MovieName").ToList();
//by genre
var moviesByGenres = context.Movies.Include(x => x.Genres).Where(x => x.Genres.Any(x => x.Name == "Action")).ToList();