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  • 分割一个表到多个实体<EntityFramework6.0>

    声明方式

     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>()
                    //配置必需关系。 数据库中的外键不可为 null否则无法保存到数据库。
                    .HasRequired(p => p.PhotographFullImage)
                    //作为关系目标的主体类型将成为依赖对象,且包含主体的外键
                    .WithRequiredPrincipal(p => p.Photograph);               
                modelBuilder.Entity<Photograph>().ToTable("Table1");
                modelBuilder.Entity<PhotographFullImage>().ToTable("Table2");
            }
        }

    怎么使用

      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}, 压缩 {1} bytes",
                        photo.Title, photo.ThumbnailBits.Length);
                        // 显式地加载了“昂贵”的实体
                        context.Entry(photo).Reference(p => p.PhotographFullImage).Load();
                        Console.WriteLine("原始: {0} bytes",
                        photo.PhotographFullImage.HighResolutionBits.Length);
                    }
                    Console.ReadKey();
                }
             }

    生成实体结构

    运行效果

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  • 原文地址:https://www.cnblogs.com/rohelm/p/4114601.html
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