Entity Framework表拆分

Posted 2022-03-27 dgg2015

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：

 

 1 using System;
 2 using System.Collections.Generic;
 3 using System.ComponentModel.DataAnnotations;
 4 using System.ComponentModel.DataAnnotations.Schema;
 5 using System.Linq;
 6 using System.Text;
 7 using System.Threading.Tasks;
 8 
 9 namespace CodeFirstTableSplit.Model
10 
11     /// <summary>
12     /// 缩略图类
13     /// </summary>
14     public class Photograph
15     
16         /// <summary>
17         /// 设置PhotoId是主键 自动增长
18         /// </summary>
19         [Key]
20         [DatabaseGenerated(System.ComponentModel.DataAnnotations.Schema.DatabaseGeneratedOption.Identity)]
21         public int PhotoId  get; set; 
22 
23         public string Title  get; set; 
24 
25         /// <summary>
26         /// 缩略图
27         /// </summary>
28         public byte[] ThumbnailBite  get; set; 
29 
30         /// <summary>
31         /// Photograph通过导航属性引用PhotographFullImage
32         /// </summary>
33         [ForeignKey("PhotoId")]
34         public virtual PhotographFullImage PhotographFullImage  get; set; 
35     
36 

 2、PhotographFullImage实体结构：

 1 using System;
 2 using System.Collections.Generic;
 3 using System.ComponentModel.DataAnnotations;
 4 using System.ComponentModel.DataAnnotations.Schema;
 5 using System.Linq;
 6 using System.Text;
 7 using System.Threading.Tasks;
 8 
 9 namespace CodeFirstTableSplit.Model
10 
11     public class PhotographFullImage
12     
13         [Key]
14         public int PhotoId  get; set; 
15 
16         /// <summary>
17         /// 高分辨率
18         /// </summary>
19         public byte[] HighResolutionBits  get; set; 
20 
21         /// <summary>
22         /// PhotographFullImage通过导航属性引用Photograph
23         /// </summary>
24         [ForeignKey("PhotoId")]
25         public virtual Photograph Photograph  get; set; 
26     
27 

 3、创建数据上下文对象子类：

 1 using CodeFirstTableSplit.Model;
 2 using System;
 3 using System.Collections.Generic;
 4 using System.Data.Entity;
 5 using System.Linq;
 6 using System.Text;
 7 using System.Threading.Tasks;
 8 
 9 namespace CodeFirstTableSplit.DatabaseContext
10 
11     public class EFDbContext :DbContext
12     
13         public EFDbContext()
14             : base("name=Default")
15          
16 
17         public DbSet<Photograph> Photographs  get; set; 
18 
19         public DbSet<PhotographFullImage> PhotographFullImages  get; set; 
20 
21         protected override void OnModelCreating(DbModelBuilder modelBuilder)
22         
23             // 设置主体
24             modelBuilder.Entity<Photograph>().HasRequired(p => p.PhotographFullImage).WithRequiredPrincipal(t => t.Photograph);
25 
26             // 生成同一张表:设置两个实体有相同的表名
27             modelBuilder.Entity<Photograph>().ToTable("Photograph");
28             modelBuilder.Entity<PhotographFullImage>().ToTable("Photograph");
29             base.OnModelCreating(modelBuilder);
30         
31 
32 
33     
34 

 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

 1 using CodeFirstTableSplit.DatabaseContext;
 2 using CodeFirstTableSplit.Model;
 3 using System;
 4 using System.Collections.Generic;
 5 using System.Linq;
 6 using System.Text;
 7 using System.Threading.Tasks;
 8 
 9 namespace CodeFirstTableSplit
10 
11     class Program
12     
13         static void Main(string[] args)
14         
15             using (var context = new EFDbContext())
16             
17                 // 写入数据
18                 byte[] thumbBits = new byte[100];
19                 byte[] fullBits = new byte[2000];
20                 var photo = new Photograph()  Title = "李四", ThumbnailBite = thumbBits ;
21                 var fullImage = new PhotographFullImage()  HighResolutionBits = fullBits ;
22 
23                 photo.PhotographFullImage = fullImage;
24                 context.Photographs.Add(photo);
25                 // 保存
26                 context.SaveChanges();
27             
28             Console.WriteLine("创建成功");
29             Console.ReadKey();
30         
31     
32 

 6、查询数据