Question

根据上图，我有一个要求，表C需要同时引用表A和表B。

注意：：Table_C中的RefId是表A和表B的参考键。

请参考代码段

Table_A类

public partial class Table_A
{
   public int Id { get; set; }
   public string Name { get; set; }
   public virtual ICollection<Table_C> Table_C { get; set; }
}

Table_B类

public partial class Table_B
{
   public int Id { get; set; }
   public string Name { get; set; }
   public virtual ICollection<Table_C> Table_C { get; set; }
}

Table_C类

public partial class Table_C
{
   public int Id { get; set; }
   public int RefId { get; set; }
   public Type Type {get; set; }
   public virtual Table_A Table_A { get; set; }
   public virtual Table_B Table_B { get; set; }
}

Fluent API

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Entity<Table_1>()
        .Property(e => e.Name)
        .IsFixedLength();

    modelBuilder.Entity<Table_1>()
        .HasMany(e => e.Table_3)
        .WithRequired(e => e.Table_1)
        .HasForeignKey(e => e.RefId)
        .WillCascadeOnDelete(false);

    modelBuilder.Entity<Table_2>()
        .Property(e => e.Name)
        .IsFixedLength();

    modelBuilder.Entity<Table_2>()
        .HasMany(e => e.Table_3)
        .WithRequired(e => e.Table_2)
        .HasForeignKey(e => e.RefId)
        .WillCascadeOnDelete(false);
}

但是，使用上面显示的代码尝试达到此要求时，会发生以下错误。

INSERT语句与FOREIGN KEY约束冲突 “ FK_dbo.TableC.TableA_Id”。数据库“ TestDB”中发生了冲突，表“ dbo.TableA”的“ Id”列。该声明已终止

如何使用Entity Framework 6（SQL Server 2014，.NET Framework 4.6.1）实现此功能？

Answer 1

似乎对我来说很好：

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Data;
using System.Data.Entity;
using System.IO;
using System.IO.Compression;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Ef6Test
{

    public partial class Table_A
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public virtual ICollection<Table_C> Table_C { get; } = new HashSet<Table_C>();
    }
    //Table_B Class
    public partial class Table_B
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public virtual ICollection<Table_C> Table_C { get; } = new HashSet<Table_C>();
    }
    //Table_C Class
    public partial class Table_C
    {
        public int Id { get; set; }
        public int RefId { get; set; }
        public string Type { get; set; }

        public virtual Table_A Table_A { get; set; }

        public virtual Table_B Table_B { get; set; }
    }

    class Db: DbContext
    {
        public DbSet<Table_A> Table_A { get; set; }
        public DbSet<Table_B> Table_B { get; set; }
        public DbSet<Table_C> Table_C { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {


            modelBuilder.Entity<Table_A>()
                .HasMany(e => e.Table_C)
                .WithRequired(e => e.Table_A)
                .HasForeignKey(e => e.RefId)
                .WillCascadeOnDelete(false);

            modelBuilder.Entity<Table_B>()
                .HasMany(e => e.Table_C)
                .WithRequired(e => e.Table_B)
                .HasForeignKey(e => e.RefId)
                .WillCascadeOnDelete(false);
        }
    }


    class Program
    {
        static void Main(string[] args)
        {

            Database.SetInitializer(new DropCreateDatabaseAlways<Db>());

            using (var db = new Db())
            {
                db.Database.Log = m => Console.WriteLine(m);
                db.Database.Initialize(true);

                var a = new Table_A();
                var b = new Table_B();
                var c = new Table_C();

                a.Table_C.Add(c);
                b.Table_C.Add(c);

                db.Table_A.Add(a);
                db.Table_B.Add(b);
                db.Table_C.Add(c);

                db.SaveChanges();
            }
            Console.ReadKey();

        }
    }
}

Answer 2

我使用@David Browne - Microsoft的评论设法满足了这一要求。因此，使用多列来引用多个相关表是这种情况的方法。希望这会对寻求此类问题答案的任何人有所帮助。感谢@David Browne - Microsoft的宝贵意见。

如何使用另一个表中的列引用两个表-Entity Framework

2 个答案: