Entity Framework表拆分為多個(gè)實(shí)體

更新時(shí)間：2022年03月05日 09:44:04 作者：.NET開發(fā)菜鳥

這篇文章介紹了Entity Framework表拆分為多個(gè)實(shí)體的方法，文中通過示例代碼介紹的非常詳細(xì)。對(duì)大家的學(xué)習(xí)或工作具有一定的參考借鑒價(jià)值，需要的朋友可以參考下

概念

表拆分：一個(gè)表拆分成多個(gè)實(shí)體，例如Photograph表，可以拆分為Photograph和PhotographFullImage兩張表。

1、Photograph實(shí)體結(jié)構(gòu)：

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>
    /// 縮略圖類
    /// </summary>
    public class Photograph
    {
        /// <summary>
        /// 設(shè)置PhotoId是主鍵 自動(dòng)增長
        /// </summary>
        [Key]
        [DatabaseGenerated(System.ComponentModel.DataAnnotations.Schema.DatabaseGeneratedOption.Identity)]
        public int PhotoId { get; set; }

        public string Title { get; set; }

        /// <summary>
        /// 縮略圖
        /// </summary>
        public byte[] ThumbnailBite { get; set; }

        /// <summary>
        /// Photograph通過導(dǎo)航屬性引用PhotographFullImage
        /// </summary>
        [ForeignKey("PhotoId")]
        public virtual PhotographFullImage PhotographFullImage { get; set; }
    }
}

2、PhotographFullImage實(shí)體結(jié)構(gòu)：

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通過導(dǎo)航屬性引用Photograph
        /// </summary>
        [ForeignKey("PhotoId")]
        public virtual Photograph Photograph { get; set; }
    }
}

3、創(chuàng)建數(shù)據(jù)上下文對(duì)象子類：

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)
        {
            // 設(shè)置主體
            modelBuilder.Entity<Photograph>().HasRequired(p => p.PhotographFullImage).WithRequiredPrincipal(t => t.Photograph);

            // 生成同一張表:設(shè)置兩個(gè)實(shí)體有相同的表名
            modelBuilder.Entity<Photograph>().ToTable("Photograph");
            modelBuilder.Entity<PhotographFullImage>().ToTable("Photograph");
            base.OnModelCreating(modelBuilder);
        }


    }
}

4、使用數(shù)據(jù)遷移生成數(shù)據(jù)庫結(jié)構(gòu)，查看生成后的結(jié)構(gòu)：

5、寫入數(shù)據(jù)

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())
            {
                // 寫入數(shù)據(jù)
                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("創(chuàng)建成功");
            Console.ReadKey();
        }
    }
}