Question

之前我曾问过类似的问题，但想发布一个更新的问题并包含说明所需的所有必要代码：

我有2个实体;购物车和购物者。他们有1：1的关系。有时我不想加载导航属性来读取FK值。我已经创建了如下所述的实体并设置了购物车和购物者之间的关系（参见下面的映射类），但EF没有在实体上填充FK属性（参见下面的单元测试）。

using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Data.Entity.ModelConfiguration;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace ClassLibrary1
{
    public class Cart
    {
        public int ID { get; set; }
        public int ShopperID { get; set; }
        public virtual  Shopper Shopper { get; set; }
    }

    public class Shopper
    {
        public int ID { get; set; }
        public int CartID { get; set; }
        public virtual Cart Cart { get; set; }
    }

    public class CartMap:EntityTypeConfiguration<Cart>
    {
        public CartMap()
        {
            this.HasKey(t => t.ID);

            // Properties

            // Table & Column Mappings
            this.ToTable("Cart", "Cart2");
            this.Property(t => t.ID).HasColumnName("ID");
            this.Property(t => t.ShopperID).HasColumnName("ShopperID");
            //this.HasRequired(t => t.Shopper)
            //    .WithRequiredPrincipal(t => t.Cart);
        }

    }

    public class ShopperMap : EntityTypeConfiguration<Shopper>
    {
        public ShopperMap()
        {
            this.HasKey(t => t.ID);

            // Properties

            // Table & Column Mappings
            this.ToTable("Shopper", "Cart2");
            this.Property(t => t.ID).HasColumnName("ID");
            this.Property(t => t.CartID).HasColumnName("CartID");

            //// Relationships
            this.HasRequired(t => t.Cart)
                .WithRequiredDependent(t => t.Shopper)
                .WillCascadeOnDelete(true);
        }
    }

    public class CartDbContext : DbContext
    {
        public IDbSet<Cart> Carts { get; set; }
        public IDbSet<Shopper> Shoppers { get; set; }
        public CartDbContext():base("name=CartTest")
        {

        }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);
            modelBuilder.Configurations.Add(new CartMap());
            modelBuilder.Configurations.Add(new ShopperMap());
        }
    }

    public class DBSeedingData : DropCreateDatabaseAlways<CartDbContext>
    {
        protected override void Seed(CartDbContext context)
        {
            var cart1 = new Cart{Shopper = new Shopper()};
            var cart2 = new Cart {Shopper = new Shopper()};
            base.Seed(context);
            context.Carts.Add(cart1);
            context.Carts.Add(cart2);
            context.SaveChanges();
        }
    }

    [TestClass]
    public class TestClass
    {
        [ClassInitialize]
        public static void RunOnceForAllTests(TestContext testContext)
        {
            Console.WriteLine("Initializing Database");
            using (var ctx = new CartDbContext())
            {
                try
                {
                    Database.SetInitializer(new DBSeedingData());
                    ctx.Database.Initialize(true);
                    Console.WriteLine("Database Dropped, Created & Seeded.");
                }
                catch (Exception ex)
                {
                    throw ex;
                }
            }
        }
        [TestMethod]
        public void CanReadAllCarts()
        {
            using (var ctx = new CartDbContext())
            {
                foreach (var cart in ctx.Carts)
                {
                    Console.WriteLine(" actual: Cart Id: {0} Shopper Id: {1} Shopper's Cart Id: {2}", cart.ID, cart.ShopperID, cart.Shopper.CartID);
                    Assert.IsTrue(cart.ID > 0, "Cart PK was not set");
                    Assert.IsTrue(cart.ShopperID > 0, "Shopper FK in Cart was not set");
                    Assert.IsNotNull(cart.Shopper, "Failed to load navigation properties");
                    Assert.IsTrue(cart.Shopper.CartID > 0, "Cart FK in Shopper was not set");
                }    
            }    
        }
    }  
}

我在这里缺少什么？我一直试图解决这个问题一周。

Answer 1

我以前经历过这种情况，也很难在EF中做一对一。我们做了一个工作，其中只有两个实体之间有一个导航属性。在您的情况下，选择是否将导航属性放在Cart或Shopper类中。基本上，这是EF中的映射，其中只有一侧具有nav属性。缺点是没有导航属性的那个是盲目的，你无法分辨它与谁有关。这是关于它的article。

假设您将nav属性放在Shopper类

中

public class Cart
{
    public int ID { get; set; }

    // no nav property for Shopper
}

public class Shopper
{
    public int ID { get; set; }
    public int CartID { get; set; }
    public virtual Cart Cart { get; set; }
}

然后你会像这样映射它：

public class ShopperMap : EntityTypeConfiguration<Shopper>
{
    public ShopperMap()
    {
        // other mappings

        // mapping to cart, notice that the WithMany() is empty           
        this.HasRequired(t => t.Cart)
            .WithMany()
            .HasForeignKey(t => t.CartID);
    }
}

您将在文章中看到EF Code-First（或一般的EF）不支持一对一的外键关联。这项工作为我们工作，所以我希望它也适合你。

实体框架1：1关系FK

1 个答案: