试图添加一个实体，但也插入另一个实体到 db

Question

我有三个实体：产品、项目（由一个产品和客户购买的产品数量组成）和因素如下：

public class Factor
{
    [Key,DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public virtual int FactorId { get; set; }
    [Required]
    public virtual System.Guid TrackingCode { set; get; }
    [StringLength(1000)]
    public string StatusOfFactor { set; get; }
    [Required, DataType(DataType.EmailAddress), StringLength(200)]
    public string EmailOfFactor { set; get; }
    // price before discount
    public virtual double PriceOfFactor { set; get; }
    public virtual double DiscountOfFactor { set; get; }
    [StringLength(3000,MinimumLength =0)]
    public virtual string GeneralDescription { set; get; }
    public virtual List<Item> Items { set; get; }
}


public class Item
{
    //[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int ItemId { set; get; }
    public int Count { set; get; }
    // 1 -> 1 relationship between product and Item
    public virtual Product Product { set; get; }
    // * -> * relationship between Item and Factor
    public virtual List<Factor> Factors { set; get; }
}


public class Product
{
    [Key,DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public virtual int ProductId { set; get; }
    [Required]
    [StringLength(128)]
    public virtual string NameFa { set; get; }
    [Required]
    [Range(0, 990000000)]
    public virtual double Price { set; get; }
    // many->many relationship category and product
    public virtual List<Category> Categories { set; get; }
    //public virtual List<Factor> Factors { get; set; }
    public virtual Item Item { set; get; }
}

实体之间的关系如下： 1 -> 1 在 Product-Item 和 * -> * 在 Item-Factor

public class ProductConfig:EntityTypeConfiguration<Product>
{
    public ProductConfig() {
        // one to one relationship between product and item
        HasOptional(p => p.Item).WithRequired(i => i.Product);
    }
}

和

public class FactorConfig : EntityTypeConfiguration<Factor>
{
    public FactorConfig( ) {
       HasMany(p => p.Items)
      .WithMany(p => p.Factors)
      .Map(c => {
          c.ToTable("ItemsFactors");
          c.MapLeftKey("FactorID");
          c.MapRightKey("ItemID");
      });
    }
}

当我在数据库中插入一个因子时，另一个产品也会添加到产品表中！！！ 这是向 db 插入因子的代码：

[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult RegisterFactor( [Bind(Include = "FactorId,TrackingCode,RegistrationDate,PaymentSucceed,PaymentIdOfBank,PaymentDate,StatusOfFactor,EmailOfFactor,TranmissionSucceed,TransmissionDate,PriceOfFactor,DiscountOfFactor,GeneralDescription,IsReturned,ReturnedDate,ReturnedDescription")]Factor factor )  
{  
    {
        // Session consist of Items and Items consist of Products
        List<Item> purchasedItems =
        (List<Item>)Session[Constants.SHOPPINGBAG];
        double totalPriceBeforeDiscount = 0.0d; 
        double totalDiscount = 0.0d;            
        double totalPriceAfterDiscount = 0.0; 
        //
        Guid trackingCode = Guid.NewGuid();
        factor.Items = new List<Item>();
        if ( purchasedItems == null )
        {
            return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
        }
        foreach ( Item item in purchasedItems )
        {
            if ( item.Product != null )
            {
                factor.Items.Add(item);
            }
        }
        // allocate data to factor
        factor.PriceOfFactor = totalPriceBeforeDiscount;
        factor.DiscountOfFactor = totalDiscount;
        factor.PaymentDate = DateTime.Now;
        factor.RegistrationDate = DateTime.Now;
        factor.TrackingCode = trackingCode;
        if ( ModelState.IsValid )
        {
            //db.Factors.AsNoTracking();
            db.Products.AsNoTracking();
            db.Factors.Add(factor);
            db.SaveChanges();
            EmptyShoppingCart();
            return View("RegisterFactorSucceed", factor);
        }
        return View(factor);
    }
}

这真的很尴尬（对我来说）。为什么会这样？

Answer 1

您的“ProductConfig”表示只要 Item 具有“product”，则应将其添加到 Product 表中。这是修改后的代码。

ProductConfig 类

public class ProductConfig : EntityTypeConfiguration<Product>
{
    public ProductConfig()
    {
        // one to one relationship between product and item
        HasOptional(p => p.Item).WithOptionalDependent(i => i.Product);
    }
}

如果您将 Item.Product 更改为 null，则它不会添加到 Product 表中。

foreach (Item item in purchasedItems)
        {
            if (item.Product != null)
            {
                factor.Items.Add(item);
                item.Product = null;//Setting Product to null
            }
        }

Answer 2

问题很可能是您的 Factor 对象引用了您要传回 EF 的内存中的产品。因此，EF 将其解释为新产品并将其与因子一起添加。

你需要……

1. 不要将填充的产品与您添加的因素一起传递到内存中，并使用 Id 链接它
2. 确保在保存之前从数据库中加载要附加因子的现有产品并进行跟踪。

我认为https://msdn.microsoft.com/en-gb/magazine/dn166926.aspx 可能会有所帮助。