在 ef core 中的表设置中添加另一个外键

Question

我正在与 ef 一起从事 .net 核心项目。 我有两张桌子：

    public class Asset
    {
        [Key]
        public Guid Id { get; set; }
        
        public string Name { get; set; }
        public string Description { get; set; }
        
        // Relationships
        public ICollection<AssetMixRecord> AssetMixRecords { get; set; }
    }

    public class AssetMixRecord
    {        
        public decimal Percentage { get; set; }        
        public Guid AssetId { get; set; }

        // Relationships
        public Guid ParentAssetId { get; set; }
    }

上下文如下所示：

            modelBuilder.Entity<Asset>()
                .HasMany(a => a.AssetMixRecords)
                .WithOne()
                .OnDelete(DeleteBehavior.Cascade);

            modelBuilder.Entity<AssetMixRecord>()
                .HasKey(c => new { c.ParentAssetId, c.AssetId })
                .IsClustered();

此迁移代码如下所示：

            migrationBuilder.CreateTable(
                name: "AssetMixRecords",
                columns: table => new
                {
                    AssetId = table.Column<Guid>(nullable: false),
                    ParentAssetId = table.Column<Guid>(nullable: false),
                    Percentage = table.Column<decimal>(type: "decimal(8,7)", nullable: false)
                },
                constraints: table =>
                {
                    table.PrimaryKey("PK_AssetMixRecords", x => new { x.ParentAssetId, x.AssetId })
                        .Annotation("SqlServer:Clustered", true);
                    table.ForeignKey(
                        name: "FK_AssetMixRecords_Assets_AssetId",
                        column: x => x.AssetId,
                        principalTable: "Assets",
                        principalColumn: "Id",
                        onDelete: ReferentialAction.Cascade);
                });

这一切都很好。但是“ParentAssetId”也是“Assets.Id”的外键。

我们的用例如下所示：

var asset1 = new Asset();
            var asset2 = new Asset();

            dbContext.Add(asset1);
            dbContext.Add(asset2);
            dbContext.SaveChanges();

            var asset3 = new Asset();

            asset3.AssetMixRecords.Add(new AssetMixRecord()
            {
                AssetId = asset1.Id,
                ParentAssetId = asset3.Id
            });

            asset3.AssetMixRecords.Add(new AssetMixRecord()
            {
                AssetId = asset2.Id,
                ParentAssetId = asset3.Id
            });

            dbContext.Add(asset3);
            dbContext.SaveChanges();

我无法将第二个外键放入迁移代码中。我应该手动添加吗？

感谢和问候

S.

Answer 1

请查看我的完整演示解决方案，它将生成以下迁移。我不确定DeleteBehavior.Cascade 是否可以使用这种架构，EF 迁移工具抱怨循环依赖。

migrationBuilder.DropForeignKey(
    name: "FK_AssetMixRecords_Assets_AssetId",
    table: "AssetMixRecords");

migrationBuilder.AddForeignKey(
    name: "FK_AssetMixRecords_Assets_AssetId",
    table: "AssetMixRecords",
    column: "AssetId",
    principalTable: "Assets",
    principalColumn: "Id");

migrationBuilder.AddForeignKey(
    name: "FK_AssetMixRecords_Assets_ParentAssetId",
    table: "AssetMixRecords",
    column: "ParentAssetId",
    principalTable: "Assets",
    principalColumn: "Id");

演示本身如下。请注意Asset 内部有 2 个导航属性。 EF 将根据子实体的位置（AssetId 或 ParentAssetId）加载那里的子实体

using Microsoft.EntityFrameworkCore;
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;

namespace ConsoleApp9
{
    public class Asset
    {
        [Key]
        public Guid Id { get; set; }

        public string Name { get; set; }
        public string Description { get; set; }

        // items where AssetMixRecord.AssetId == Id
        public ICollection<AssetMixRecord> AssetMixRecords { get; set; }

        // items where AssetMixRecord.ParentAssetId == Id
        public ICollection<AssetMixRecord> ParentAssetMixRecords { get; set; }
    }

    public class AssetMixRecord
    {
        public decimal Percentage { get; set; }
        public Guid AssetId { get; set; }
        public virtual Asset Asset { get; set; }
        public Guid ParentAssetId { get; set; }
        public virtual Asset ParentAsset { get; set; }
    }

    public class ApplicationDbContext : DbContext
    {
        public DbSet<Asset> Assets { get; set; }
        public DbSet<AssetMixRecord> AssetMixRecords { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseSqlServer("Server=DESKTOP-1111111;Database=testef11db;Integrated Security=true;");

            base.OnConfiguring(optionsBuilder);
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Asset>()
                .HasMany(a => a.AssetMixRecords)
                .WithOne(x => x.Asset)
                .HasForeignKey(x => x.AssetId)
                .OnDelete(DeleteBehavior.NoAction);

            modelBuilder.Entity<Asset>()
                .HasMany(x => x.ParentAssetMixRecords)
                .WithOne(x => x.ParentAsset)
                .HasForeignKey(x => x.ParentAssetId)
                .OnDelete(DeleteBehavior.NoAction);

            modelBuilder.Entity<AssetMixRecord>()
                .HasKey(c => new { c.ParentAssetId, c.AssetId })
                .IsClustered();

            base.OnModelCreating(modelBuilder);
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            var dbContext = new ApplicationDbContext();

            var asset1 = new Asset();
            var asset2 = new Asset();

            dbContext.Add(asset1);
            dbContext.Add(asset2);
            dbContext.SaveChanges();

            var assetDataMixRecord = new AssetMixRecord()
            {
                AssetId = asset1.Id,
                ParentAssetId = asset2.Id
            };

            dbContext.Add(assetDataMixRecord);
            dbContext.SaveChanges();

            var assets = dbContext.Assets
                .Include(x => x.AssetMixRecords)
                .Include(x => x.ParentAssetMixRecords)
                .ToList();
        }
    }
}

如果您不想 ParentAssetId 等于 ChildAssetId，只需将下面的代码添加到上面的解决方案中

modelBuilder.Entity<AssetMixRecord>()
    .HasCheckConstraint("PK_Check_ChildAssetId_And_ParentAssetId", "ParentAssetId != ChildAssetId");

如果您将AssetMixRecords 更改为ParentAssetMixRecords for asset3，您的用例将正常工作

var dbContext = new ApplicationDbContext();
var asset1 = new Asset();
var asset2 = new Asset();

dbContext.Add(asset1);
dbContext.Add(asset2);
dbContext.SaveChanges();

var asset3 = new Asset();

asset3.ParentAssetMixRecords.Add(new AssetMixRecord()
{
    AssetId = asset1.Id,
    ParentAssetId = asset3.Id
});

asset3.ParentAssetMixRecords.Add(new AssetMixRecord()
{
    AssetId = asset2.Id,
    ParentAssetId = asset3.Id
});

dbContext.Add(asset3);
dbContext.SaveChanges();