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Entity Framework表拆分为多个实体_实用技巧_

2023-05-24 503人已围观

简介 Entity Framework表拆分为多个实体_实用技巧_

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。

1、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 { ///  /// 缩略图类 /// 
 public class Photograph { ///  /// 设置PhotoId是主键 自动增长 /// 
 [Key] [DatabaseGenerated(System.ComponentModel.DataAnnotations.Schema.DatabaseGeneratedOption.Identity)] public int PhotoId { get; set; } public string Title { get; set; } ///  /// 缩略图 /// 
 public byte[] ThumbnailBite { get; set; } ///  /// Photograph通过导航属性引用PhotographFullImage /// 
 [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; } ///  /// 高分辨率 /// 
 public byte[] HighResolutionBits { get; set; } ///  /// PhotographFullImage通过导航属性引用Photograph /// 
 [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 Photographs { get; set; } public DbSet PhotographFullImages { get; set; } protected override void OnModelCreating(DbModelBuilder modelBuilder) { // 设置主体 modelBuilder.Entity().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().ToTable("Photograph"); modelBuilder.Entity().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[100]; byte[] fullBits = new byte[2000]; 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(); } } }