分割一個表到多個實體

聲明方式

 public class Photograph
    {
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int PhotoId { get; set; }
        public string Title { get; set; }
        public byte[] ThumbnailBits { get; set; }
        [ForeignKey("PhotoId")]
        public virtual PhotographFullImage PhotographFullImage { get; set; }
    }

    public class PhotographFullImage
    {
        [Key]
        public int PhotoId { get; set; }
        public byte[] HighResolutionBits { get; set; }
        [ForeignKey("PhotoId")]
        public virtual Photograph Photograph { get; set; }
    }

    public class PhotoContext : DbContext
    {
        public DbSet<Photograph> Photographs { get; set; }
        public DbSet<PhotographFullImage> PhotographFullImages { get; set; }
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);
            modelBuilder.Entity<Photograph>()
                //配置必需關係。 數據庫中的外鍵不可爲 null不然沒法保存到數據庫。
                .HasRequired(p => p.PhotographFullImage)
                //做爲關係目標的主體類型將成爲依賴對象，且包含主體的外鍵
                .WithRequiredPrincipal(p => p.Photograph);               
            modelBuilder.Entity<Photograph>().ToTable("Table1");
            modelBuilder.Entity<PhotographFullImage>().ToTable("Table2");
        }
    }

怎麼使用

  static void Main(string[] args)
        {
            var thumbBits = new byte[100];
            var fullBits = new byte[2000];
            using (var context = new PhotoContext())
            {
                var photo = new Photograph
                {
                    Title = "小狗",
                    ThumbnailBits = thumbBits
                };
                var fullImage = new PhotographFullImage { HighResolutionBits = fullBits };
                photo.PhotographFullImage = fullImage;
                context.Photographs.Add(photo);
                context.SaveChanges();
            }
            using (var context = new PhotoContext())
            {
                foreach (var photo in context.Photographs)
                {
                    Console.WriteLine("照片: {0}, 壓縮 {1} bytes",
                    photo.Title, photo.ThumbnailBits.Length);
                    // 顯式地加載了「昂貴」的實體
                    context.Entry(photo).Reference(p => p.PhotographFullImage).Load();
                    Console.WriteLine("原始: {0} bytes",
                    photo.PhotographFullImage.HighResolutionBits.Length);
                }
                Console.ReadKey();
            }
         }

生成實體結構

運行效果