学步园

数据库中有这样的三张表，Artist，Album，ArtistAlbum

 

Artist和Album是多对多的关系，ArtistAlbum 是Artist和Album的关联表。ArtistAlbum 是双主键，除了Artist和Album表的ID外没有其他任何其他字段。

新建一个项目，添加一个ADO.NET Entity Data Model，在数据库中选择上面三张表：

 

EMD中并没有关联表ArtistAlbum并没有作为一个实体呈现在EDM中 

  下面的代码是向Artist和Album表添加新的数据和在model中查询Artist的Album以及Album所属的Artist

 

            using (EFDemoEntities context = new EFDemoEntities())
            {
                // add an artist with two albums
                var artist = new Artist { ArtistName = "徐悲鸿" };
                var album1 = new Album { AlbumName = "八骏图" };
                var album2 = new Album { AlbumName = "八丑图" };
                artist.Albums.Add(album1);
                artist.Albums.Add(album2);
                context.Artists.AddObject(artist);
                // add an album for two artists
                var artist1 = new Artist { ArtistName = "zjz" };
                var artist2 = new Artist { ArtistName = "张大千" };
                var album = new Album { AlbumName = "大虾图" };
                artist1.Albums.Add(album);
                artist2.Albums.Add(album);
                context.Albums.AddObject(album);
                context.SaveChanges();
            }
            using (EFDemoEntities context = new EFDemoEntities())
            {
                Console.WriteLine("Artists and their albums...");
                var artists = from a in context.Artists select a;
                foreach (var artist in artists)
                {
                    Console.WriteLine("{0}", artist.ArtistName);
                    foreach (var album in artist.Albums)
                    {
                        Console.WriteLine("\t{0}", album.AlbumName);
                    }
                }
                Console.WriteLine("\nAlbums and their artists...");
                var albums = from a in context.Albums select a;
                foreach (var album in albums)
                {
                    Console.WriteLine("{0}", album.AlbumName);
                    foreach (var artist in album.Artists)
                    {
                        Console.WriteLine("\t{0}", artist.ArtistName);
                    }
                }
            }

 

输出结果如下：