EF框架一对多 多对多关系总结

原文连接 https://blog.csdn.net/hhhhhhenrik/article/details/89216909

总结几种项目中遇到的一对多 多对多关系

1 基本的多对多关系

  public class npc
  {
      public string Name;
      public ICollection<Content> Contents;
  }

  public class Content
  {
      public string Name;

      public ICollection<npc> npcs;
  }

  //fluent api
  HasMany(m => m.Contents).WithMany(w => w.npcs).Map(m =>
  {
      m.ToTable("C_NPC_Content_Relation");
      m.MapLeftKey("npcId");
      m.MapRightKey("ContentId");
  });
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2 同一个表建立两个多对多关系

    public class npc
    {
        public string Name;
        public ICollection<Content> Contents1;
        public ICollection<Content> Contents2;
    }

    public class Content
    {
        public string Name;

        public ICollection<npc> npcs;
    }
     //fluent api
    HasMany(m => m.Contents1).WithMany(w => w.npcs).Map(m =>
    {
        m.ToTable("C_NPC_Content1_Relation");
        m.MapLeftKey("npcId");
        m.MapRightKey("ContentId");
    });
    HasMany(m => m.Contents2).WithMany().Map(m =>
    {
        m.ToTable("C_NPC_Content2_Relation");
        m.MapLeftKey("npcId");
        m.MapRightKey("ContentId");
    });
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3 普通的一对多

   public class npc
   {
       public string Name;
       public int ContentId;//外键
   }

   public class Content
   {
       public string Name;
       public ICollection<npc> npcs;
   }
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4 同一个表建立两份一对多关系

   public class npc
   {
        public string Name;
        public int ContentId_1;//外键1
        public int ContentId_2;//外键2
    }

    public class Content
    {
        public string Name;
        public ICollection<npc> npcs_1;
        public ICollection<npc> npcs_2;
    }
    //fluent api(npc)
     this.HasRequired(t => t.Content)
       .WithMany(t => t.npcs_1)
       .HasForeignKey(t => t.ContentId_1)
       .WillCascadeOnDelete(false);
     this.HasOptional(t => t.Content)
        .WithMany(t => t.npcs_2)
        .HasForeignKey(t => t.ContentId_2)
        .WillCascadeOnDelete(false);
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