Entity Framework Code First 一對多關聯設定

2014-11-25 16:17:00

兩個類別之間，一個包含集合導覽屬性，一個包含引用屬性，就會被當成一對多關系

主表

namespace ConsoleApplication1.Models
{
    using System.Collections.Generic;
    using System.ComponentModel.DataAnnotations.Schema;

    [Table(“Topic”)]
    public class Topic
    {
        public int TopicId { get; set; }

        public string Title { get; set; }

        public virtual ICollection<Reply> Reply { get; set; }
    }
}

明細表
外鍵的命名只有符合預設的規則，就會建立關系，規則如下
1. 目標類型索引的名稱
2. 目標類型名稱+目標類型主索引名稱
3. 導覽屬性名稱+目標類型主索引名稱

namespace ConsoleApplication1.Models
{
    using System.ComponentModel.DataAnnotations.Schema;

    [Table(“Reply”)]
    public class Reply
    {
        public int ReplyId { get; set; }

        public int TopicId { get; set; }
        // public int TopicTopicId { get; set; }
        // public int TheTopicTopicId { get; set; }

        public string Title { get; set; }

        public virtual Topic TheTopic { get; set; }
    }
}

若不是用預設規則的命名方式，可以透過ForeignKey這個Attribute設定

namespace ConsoleApplication1.Models
{
    using System.ComponentModel.DataAnnotations.Schema;

    [Table(“Reply”)]
    public class Reply
    {
        public int ReplyId { get; set; }

        [ForeignKey(“TheTopic”)]
        public int tid { get; set; }

        public string Title { get; set; }

        public virtual Topic TheTopic { get; set; }
    }
}

也可以設定在引用屬性上

namespace ConsoleApplication1.Models
{
    using System.ComponentModel.DataAnnotations.Schema;

    [Table(“Reply”)]
    public class Reply
    {
        public int ReplyId { get; set; }

        public int tid { get; set; }

        public string Title { get; set; }

        [ForeignKey(“tid”)]
        public virtual Topic TheTopic { get; set; }
    }
}

透過FluentAPI設定方式

namespace ConsoleApplication1.Models
{
    using System.Data.Entity;

    public class DemoContext : DbContext
    {
        public DbSet<Topic> Topic { get; set; }

        public DbSet<Reply> Reply { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Topic>()
                .HasMany(x => x.Reply)
                .WithRequired(x => x.TheTopic)
                .HasForeignKey(x => x.tid)
                .WillCascadeOnDelete(true);
        }
    }
}

資料表建立的樣子

關聯圖

Code First, Entity Framework