EF Core 种子数据库与预定义列表的一对多关系

我试图在我的数据库中使用定义的 List 建立 OneToMany 关系，并收到以下错误消息

'无法添加实体类型“Country”的种子实体，因为它设置了导航“WineRegions”。要种子关系，您需要将相关实体种子添加到“WineRegion”并指定外键值 {'CountryId'}。考虑使用“DbContextOptionsBuilder.EnableSensitiveDataLogging”来查看涉及的属性值。

我使用此页面来创建我的课程：https://www.learnentityframeworkcore.com/relationships#one-to-many https://www.learnentityframeworkcore.com/relationships#one-to-many...我只能猜测我以某种方式需要手动定义键，即使它应该自动工作...

这是我的两副眼镜。葡萄酒产区包含一个国家/地区，而国家/地区包含一系列葡萄酒产区：

public class WineRegion
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int WineRegionId { get; set; }

    public string WineRegionName { get; set; }   

    public int CountryId { get; set; }
    public Country Country { get; set; }
}

public class Country
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int CountryId { get; set; }

    [Required]
    [MaxLength(255)]
    public string CountryName { get; set; }

    [Required]
    [MaxLength(2)]
    public string ISO3166Alpha2 { get; set; }

    public ICollection<WineRegion> WineRegions { get; set; }
}

在播种期间，我不想使用硬编码对象，例如（顺便说一句，此代码有效......）：

        modelBuilder.Entity<Country>().HasData(
            new { Id = 1, Name = "France", ISO3166Alpha2 = "FR" }
            );

        modelBuilder.Entity<WineRegion>().HasData(
            new { Id = 1, Name = "Bordeaux", CountryId = 1 }
            );

正如我之前提到的，我想使用在 JSON 解析过程中生成的列表。

所以这就是我所做的：

        modelBuilder.Entity<Country>().HasData(listOfCountries);  // List<Country>
        modelBuilder.Entity<WineRegion>().HasData(listOfWineRegions); //List<WineRegion>

我的 JSON 看起来像这样：

  "wineregions": [
    {
      "id": 1,
      "country": "France",
      "iso2": "FR",
      "region": [
        {
          "id": 1,
          "name": "Bordeaux"
        },
        {
          "id": 2,
          "name": "Burgundy"
        },
        {
          "id": 4,
          "name": "Burgundy"
        },
        {
          "id": 5,
          "name": "Beaujolais"
        },
        {
          "id": 6,
          "name": "Champagne"
        },
        {
          "id": 7,
          "name": "Loire"
        },
        {
          "id": 8,
          "name": "Alsace"
        },
        {
          "id": 9,
          "name": "Rhône"
        },
        {
          "id": 10,
          "name": "Provence"
        },
        {
          "id": 11,
          "name": "Languedoc-Roussillon"
        },
        {
          "id": 12,
          "name": "Jura"
        }
      ]
    },
    {
      "id": 2,
      "country": "Italy",
      "iso2": "IT",
      "region": [
        {
          "id": 1,
          "name": "Piedmont"
        },
        {
          "id": 2,
          "name": "Barolo"
        },
        {
          "id": 3,
          "name": "Barbaresco"
        },
        {
          "id": 4,
          "name": "Tuscany"
        },
        {
          "id": 5,
          "name": "Veneto"
        },
        {
          "id": 6,
          "name": "Friuli-Venezia"
        },
        {
          "id": 7,
          "name": "Giulia"
        },
        {
          "id": 8,
          "name": "Abruzzo"
        },
        {
          "id": 9,
          "name": "Sicily"
        },
        {
          "id": 10,
          "name": "Lambrusco"
        }
      ]
    }
  ]
} 


Thanks in advance

Your WineRegionId and ConutryId是 Identity 并且由 SQL 自动生成。

当您的数据库密钥是身份时Id = 1 doesn't work.

您应该从中删除身份CountryId and WineRegionId.

[Key]
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public int CountryId { get; set; }

[Key]
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public int WineRegionId { get; set; }

其他方式

您可以将代码更改为此。

Country country = new Country { Name = "France", ISO3166Alpha2 = "FR" };
modelBuilder.Entity<Country>().HasData(country);

modelBuilder.Entity<WineRegion>().HasData(
            new { Name = "Bordeaux", Country = country }
            );

在这种情况下ConutryId and WineRegionId自动生成SQL以及之间的关系Conutry and WineRegion由该行创建

new { Name = "Bordeaux", Country = country/*<--NOTE THIS*/ }