Entity Framework表拆分

Bertha 。 2023-06-01 11:27 32阅读 0赞

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：

![复制代码][Image 1]

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 }

![复制代码][Image 1]

2、PhotographFullImage实体结构：

![复制代码][Image 1]

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 }

![复制代码][Image 1]

3、创建数据上下文对象子类：

![复制代码][Image 1]

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 }

![复制代码][Image 1]

4、使用数据迁移生成数据库结构，查看生成后的结构：

![1033738-20171209001732984-1033871002.png][]

5、写入数据

![复制代码][Image 1]

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 }

![复制代码][Image 1]

6、查询数据

![1033738-20171209002000327-564291502.png][]

转载于:https://www.cnblogs.com/dgg2015/p/11152657.html

[Image 1]: 
[1033738-20171209001732984-1033871002.png]: /images/20230601/e0fcc3fc060e45a8acf37f9b08b2c01e.png
[1033738-20171209002000327-564291502.png]: /images/20230601/45500bdf231e45259a1205267b844927.png