Entity Framework表拆分

一、概念

表拆分：一个表拆分成多个实体，例如Photograph表，可以拆分为Photograph和PhotographFullImage两张表。

Photograph实体结构：

 using System;
 using System.Collections.Generic;
 using System.ComponentModel.DataAnnotations;
 using System.ComponentModel.DataAnnotations.Schema;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;

 namespace CodeFirstTableSplit.Model
 {
     /// <summary>
     /// 缩略图类
     /// </summary>
     public class Photograph
     {
         /// <summary>
         /// 设置PhotoId是主键 自动增长
         /// </summary>
         [Key]
         [DatabaseGenerated(System.ComponentModel.DataAnnotations.Schema.DatabaseGeneratedOption.Identity)]
         public int PhotoId { get; set; }

         public string Title { get; set; }

         /// <summary>
         /// 缩略图
         /// </summary>
         public byte[] ThumbnailBite { get; set; }

         /// <summary>
         /// Photograph通过导航属性引用PhotographFullImage
         /// </summary>
         [ForeignKey("PhotoId")]
         public virtual PhotographFullImage PhotographFullImage { get; set; }
     }
 }

2、PhotographFullImage实体结构：

 using System;
 using System.Collections.Generic;
 using System.ComponentModel.DataAnnotations;
 using System.ComponentModel.DataAnnotations.Schema;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;

 namespace CodeFirstTableSplit.Model
 {
     public class PhotographFullImage
     {
         [Key]
         public int PhotoId { get; set; }

         /// <summary>
         /// 高分辨率
         /// </summary>
         public byte[] HighResolutionBits { get; set; }

         /// <summary>
         /// PhotographFullImage通过导航属性引用Photograph
         /// </summary>
         [ForeignKey("PhotoId")]
         public virtual Photograph Photograph { get; set; }
     }
 }

3、创建数据上下文对象子类：

 using CodeFirstTableSplit.Model;
 using System;
 using System.Collections.Generic;
 using System.Data.Entity;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;

 namespace CodeFirstTableSplit.DatabaseContext
 {
     public class EFDbContext :DbContext
     {
         public EFDbContext()
             : base("name=Default")
         { }

         public DbSet<Photograph> Photographs { get; set; }

         public DbSet<PhotographFullImage> PhotographFullImages { get; set; }

         protected override void OnModelCreating(DbModelBuilder modelBuilder)
         {
             // 设置主体
             modelBuilder.Entity<Photograph>().HasRequired(p => p.PhotographFullImage).WithRequiredPrincipal(t => t.Photograph);

             // 生成同一张表:设置两个实体有相同的表名
             modelBuilder.Entity<Photograph>().ToTable("Photograph");
             modelBuilder.Entity<PhotographFullImage>().ToTable("Photograph");
             base.OnModelCreating(modelBuilder);
         }

     }
 }

4、使用数据迁移生成数据库结构，查看生成后的结构：

5、写入数据

 using CodeFirstTableSplit.DatabaseContext;
 using CodeFirstTableSplit.Model;
 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;

 namespace CodeFirstTableSplit
 {
     class Program
     {
         static void Main(string[] args)
         {
             using (var context = new EFDbContext())
             {
                 // 写入数据
                 byte[] thumbBits = new byte[];
                 byte[] fullBits = new byte[];
                 var photo = new Photograph() { Title = "李四", ThumbnailBite = thumbBits };
                 var fullImage = new PhotographFullImage() { HighResolutionBits = fullBits };

                 photo.PhotographFullImage = fullImage;
                 context.Photographs.Add(photo);
                 // 保存
                 context.SaveChanges();
             }
             Console.WriteLine("创建成功");
             Console.ReadKey();
         }
     }
 }

6、查询数据