Question

我有两个多对多数据库表

tblBook idBook 标题作家等等...

tblBookGenre ID idBook idGenre

tblGenre idGenre NameGenre

然后 tblBook idBook 标题作家等等...

tblBookTag ID idBook idGenre

tblTag idTag NameTag

我这样映射他们

 public class Book:INotifyPropertyChanged
    {
        Connection con = new Connection();

        private int _idBook;
        private string _title;
        private List<Genre> _genres;
        private List<Tag> _tag;
        private ObservableCollection<Book> _books;

      public int IdBook
        {
            get { return _idBook; }
            set { _idBook = value; }
        }

        public string Title
        {
            get { return _title; }
            set { _title = value; }
        }

       public List<Genre> Genres
        {
            get { return _genres; }
            set { _genres = value; }
        }

        public List<Tag> Tags
        {
            get { return _tag; }
            set { _tag = value; }
        }

        public ObservableCollection<Book> Books
        {
            get { return _books; }
            set { _books = value; }
        }
       public Book()
        {
            Tags = new List<Tag>();
            Books = new ObservableCollection<Book>();
            Genres = new List<Genre>();
        }

我使用sqlcommand和reader从数据库中读取


        public ObservableCollection<Book> GetBooks()
        {
            con.Open();
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = con.con;

            cmd.CommandText = "SELECT idBook,Title FROM tblBook WHERE Active = 1 ORDER BY b.idBook";
            SqlDataReader rd = cmd.ExecuteReader();
            if (rd.HasRows)
            {
                while (rd.Read())
                {
                    Book book = new Book();

                    var id = Convert.ToInt32(rd["IdBook"]);
                    var title = rd["Title"].ToString();

                    book.IdBook = id;
                    book.Title = title;

                    List<Tag> tags = GetTagsThatMatch(id);
                    book.Tags = tags;
                    book.Genres = GetGenresThatMatch(id);

                    Books.Add(book);

                }
                rd.Close();
            }
            con.Close();
            return Books;
        }


        public ObservableCollection<Tag> GetTagsThatMatch(int id)
        {
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = con.con;
            cmd.CommandText = "SELECT t.IdTag,t.Name FROM tblTag t LEFT OUTER JOIN tblBookTag bt ON bt.idTag = t.idTag WHERE bt.idBook = @ID";
            cmd.Parameters.AddWithValue("@ID", id);
            SqlDataReader rd = cmd.ExecuteReader();
            if (rd.HasRows)
            {
                while (rd.Read())
                {
                    Tag tag = new Tag();
                    tag.IdTag = Convert.ToInt32(rd["IdTag"]);
                    tag.Name = rd["Name"].ToString();
                    Tags.Add(tag);
                }
            }
            return Tags;
        }

        public List<Genre> GetGenresThatMatch(int id)
        {
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = con.con;
            cmd.CommandText = "SELECT g.Name FROM tblGenre g LEFT JOIN tblBookGenre bg ON g.IdGenre = bg.IdGenre LEFT OUTER JOIN tblBook b ON bg.IdBook = b.IdBook WHERE b.IdBook = @Id";
            cmd.Parameters.AddWithValue("@ID", id);
            SqlDataReader rd = cmd.ExecuteReader();
            if (rd.HasRows)
            {
                while (rd.Read())
                {
                    Genre genre = new Genre();
                    genre.Name = rd["Name"].ToString();
                    Genres.Add(genre);
                }
            }
            return Genres;
        }

问题是它会显示所有书籍的所有流派和标签

书1-类型1，类型2，类型3 -Tag1，Tag2，Tag3

书2-类型1，类型2，类型3 -Tag1，Tag2，Tag3

何时仅显示匹配项

书籍1-类型1，类型2 -Tag1，Tag2

Book 2-Genre3 -Tag3

我真的很想在没有ORM的情况下做到这一点，而且看起来很简单，但是如果没有ORM，我将找不到很多资源。同样，任何文章或示例都将被理解。

C＃-在没有ORM的情况下处理多对多

0 个答案: