如何访问链接表

Question

我刚刚通过实体框架Core 6.0实现了两个模型，漫画和流派之间的许多关系，该模型在我的数据库中创建了链接表GenRemanga。我正在尝试访问与特定漫画相关的所有类型，但我坚持尝试访问链接表。我的解决方案遵循存储库结构和工作模式单位。

在这个类似问题上的stackoverflow答案使我达到了这种格式：

var genres = _unitOfWork.GenreMangas.Include(a => a.Genres);

但是，我无法像其他Stackoverflow用户那样访问链接表，我会收到此错误：

'iunitofwork'不包含“ genremangas”的定义，也没有可访问的扩展方法'genremangas'接受类型“ iunitofwork”的第一个参数（您是否缺少使用指令或汇编引用？）

也许我需要更改？我如何定义和使用一些东西？我什至不确定从哪里开始。如果有人可以将我指向正确的方向，我将不胜感激。

以下是我的很多课程，但我希望它可以解释结构（或混乱）。

public class Manga
    {
        public int Id { get; set; }
        [Required]
        public string Title { get; set; }
        [Required]
        public string Description { get; set; }
        public string Status { get; set; }
        public int Chapters { get; set; }
        public DateTime Updated { get; set; }
        [Range(1,5)]
        public double Rating { get; set; }
        public int Views { get; set; }
        [ValidateNever]
        public string ImageUrl { get; set; }
        public ICollection<Genre>? Genres { get; set; }
        [Required]
        [Display(Name = "Author")]
        public int AuthorId { get; set; }
        [ValidateNever]
        public Author Author { get; set; }
    }

public class Genre
    {
        [Key]
        public int Id { get; set; }
        [Required]
        public string Name { get; set; }
        public ICollection<Manga>? Mangas { get; set; }
    }

public class MangaVM
    {
        public Manga Manga { get; set; }
        [ValidateNever]
        public List<Genre>? Genres { get; set; }
        [ValidateNever]
        public List<string> GenresList { get; set; }
        [ValidateNever]
        public IEnumerable<SelectListItem> AuthorList { get; set; }
    }

public class ApplicationDbContext : IdentityDbContext
    {
        public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options) : base(options)
        {
        }

        public DbSet<Genre> Genres { get; set; }
        public DbSet<Author> Authors { get; set; }
        public DbSet<Manga> Mangas { get; set; }
        public DbSet<Page> Pages { get; set; }
        public DbSet<Chapter> Chapters { get; set; }
        public DbSet<ApplicationUser> ApplicationUsers { get; set; }
    }

public class UnitOfWork : IUnitOfWork
    {
        private ApplicationDbContext _dbContext;

        public UnitOfWork(ApplicationDbContext dbContext)
        {
            _dbContext = dbContext;
            Genre = new GenreRepository(_dbContext);
            Author = new AuthorRepository(_dbContext);
            Manga = new MangaRepository(_dbContext);
            Page = new PageRepository(_dbContext);
            Chapter = new ChapterRepository(_dbContext);
        }
        public IGenreRepository Genre { get; private set; }
        public IAuthorRepository Author { get; private set; }

        public IMangaRepository Manga { get; private set; }
        public IPageRepository Page { get; private set; }
        public IChapterRepository Chapter { get; private set; }
        public void Save()
        {
            _dbContext.SaveChanges();
        }
    }

public interface IUnitOfWork
    {
        IGenreRepository Genre { get; }
        IAuthorRepository Author { get; }
        IMangaRepository Manga { get; }
        IPageRepository Page { get; }
        IChapterRepository Chapter { get; }
        void Save();
    }

public class MangaRepository : Repository<Manga>, IMangaRepository
    {
        private ApplicationDbContext _dbContext;

        public MangaRepository(ApplicationDbContext dbContext) : base(dbContext)
        {
            _dbContext = dbContext;

        }

        public void Update(Manga obj)
        {
            var objFromDb = _dbContext.Mangas.FirstOrDefault(a => a.Id == obj.Id);
            if (objFromDb != null)
            {
                objFromDb.Title = obj.Title;
                objFromDb.Description = obj.Description;
                objFromDb.Status = obj.Status;
                objFromDb.Chapters = obj.Chapters;
                objFromDb.Updated = obj.Updated;
                objFromDb.Rating = obj.Rating;
                objFromDb.Views = obj.Views;
                objFromDb.AuthorId = obj.AuthorId;
                if (obj.ImageUrl != null)
                {
                    objFromDb.ImageUrl = obj.ImageUrl;
                }
            }
        }
    }

public interface IMangaRepository : IRepository<Manga>
    {
        void Update(Manga obj);
    }

public class Repository<T> : IRepository<T> where T : class
    {
        private readonly ApplicationDbContext _dbContext;
        internal DbSet<T> dbSet;
        public Repository(ApplicationDbContext dbContext)
        {
            _dbContext = dbContext;
            //_dbContext.Mangas.Include(a => a.Genre).Include(a=>a.Author);
            this.dbSet = _dbContext.Set<T>();
        }
        public void Add(T entity)
        {
            dbSet.Add(entity);
        }
        //includeProp - "Genre,Author"
        public IEnumerable<T> GetAll(string? includeProperties = null)
        {
            IQueryable<T> query = dbSet;
            if(includeProperties != null)
            {
                foreach(var includeProp in includeProperties.Split(new char[] {','}, StringSplitOptions.RemoveEmptyEntries))
                {
                    query = query.Include(includeProp);
                }
            }
            return query.ToList();
        }

        public IEnumerable<T> GetDataFromDbSetUsingFk(Expression<Func<T, bool>> filter, string? includeProperties = null)
        {
            IQueryable<T> query = dbSet;
            query = query.Where(filter);
            if (includeProperties != null)
            {
                foreach (var includeProp in includeProperties.Split(new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries))
                {
                    query = query.Include(includeProp);
                }
            }
            return query.ToList();
        }

        public T GetFirstOrDefault(Expression<Func<T, bool>> filter, string? includeProperties = null)
        {
            IQueryable<T> query = dbSet;
            query = query.Where(filter);
            if (includeProperties != null)
            {
                foreach(var includeProp in includeProperties.Split(new char[] {','}, StringSplitOptions.RemoveEmptyEntries))
                {
                    query = query.Include(includeProp);
                }
            }
            return query.FirstOrDefault();
        }

        public void Remove(T entity)
        {
            dbSet.Remove(entity);
        }

        public void RemoveRange(IEnumerable<T> entity)
        {
            dbSet.RemoveRange(entity);
        }
    }

public interface IRepository<T> where T : class
    {
        //T - Genre
        T GetFirstOrDefault(Expression<Func<T, bool>> filter, string? includeProperties = null);
        IEnumerable<T> GetDataFromDbSetUsingFk(Expression<Func<T, bool>> filter, string? includeProperties = null);
        IEnumerable<T> GetAll(string? includeProperties = null);
        void Add(T entity);
        void Remove(T entity);
        void RemoveRange(IEnumerable<T> entity);
    }

解决方案Explorer pic

db pic

编辑：尝试使用建议的使用此代码，但似乎有效，但类型是无效的，即使GenRemanga表中有两个记录，用于该漫画ID。我仍然觉得它根本无法访问链接表。

var mangaGenres = _unitOfWork.Manga.GetAll().Where(a => a.Id == id).SelectMany(a => a.Genres);

mangaobj

genremanga表

Answer 1

没有多余的抽象，很容易：

var genres = await _context.Manga
    .Where(m => m.Id == mangaId)
    .SelectMany(m => m.Genres)
    .ToListAsync();

请记住，dbcontext已经是工作单位，dbset已经是存储库，