3 表關系

Question

我正在嘗試在 c# 中建立 3 個表之間的關系我的模型是：吉他：

public class Guitar
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    [Required]
    public int Id { get; set; }
    [MaxLength(30)]
    [Required]
    public string Model { get; set; }
    public int? Price { get; set; }
    [NotMapped]
    public virtual Brand Brand { get; set; }
    public int BrandId { get; set; }

牌：

public class Brand
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    [Required]
    public int Id { get; set; }
    [Required]
    public string Name { get; set; }
    [NotMapped]
    public virtual ICollection<Guitar> Guitars { get; set; }
    public Brand()
    {
        Guitars = new HashSet<Guitar>();
    }

購買：（此處可能缺少某些屬性）

public class Purchase
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    [Required]
    public int Id { get; set; }
    [Required]
    [MaxLength(40)]
    public string BuyerName { get; set; }
    
    [NotMapped]
    public virtual Guitar Guitar { get; set; }
    public int GuitarId { get; set; }
    

}

我已經設法將吉他和品牌表連接在一起，但我無法處理第三個。 到目前為止，這是我的代碼：

modelBuilder.Entity<Guitar>(entity =>
        {
            entity.HasOne(guitar => guitar.Brand)
                .WithMany(brand => brand.Guitars)
                .HasForeignKey(guitar => guitar.BrandId)
                .OnDelete(DeleteBehavior.ClientSetNull);
        });

Purchases 表中的外鍵應該是吉他的 ID，但如果你有更好的主意，我願意接受。 那么，我如何對購買做同樣的事情呢？

Answer 1

從您的課程中刪除所有 [NotMapped]，我也會添加買家 class

public class Guitar
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    [Required]
    public int Id { get; set; }
    ....
  [Required]
     public int? BrandId { get; set; }
     public virtual Brand Brand { get; set; }
  
}
  public class Brand
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    [Required]
    public int Id { get; set; }
     .....
   
    public virtual ICollection<Guitar> Guitars { get; set; }

    public Brand()
    {
        Guitars = new HashSet<Guitar>();
    }
}

public class Buyer
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    [Required]
    public int Id { get; set; }
     [Required]
    [MaxLength(40)]
    public string Name { get; set; }
   
    public virtual ICollection<Purchase> Purchases { get; set; }
    public Bayer()
    {
        Purchases = new HashSet<Purchase>();
    }
}

public class Purchase
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    [Required]
    public int Id { get; set; }

    [Required]
    public int? BuyerId { get; set; }
     public virtual Buyer Buyer { get; set; }

       [Required]
    public int? GuitarId { get; set; }
    public virtual Guitar Guitar { get; set; }
}

如果您使用的是 net core 5+，則不需要任何流利的 api