c# - Entity Framework - 在 Seed() 方法中实现一对多外键关系

Question

我有以下类(class):

楼主

[Table("Landlord")]
public class Landlord : UserProfile
{
    public static int LandlordProfileViews { get; set; }

    // A Landlord can have many ResidentialProperties
    [ForeignKey("ResidentialPropertyId")]
    public virtual ICollection<ResidentialProperty> ResidentialProperties { get; set; }

}

住宅属性(property)

[Table("ResidentialProperty")]
public class ResidentialProperty
{
    [Key]
    [DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
    public int ResidentialPropertyId { get; set; }
    // ...

    // A ResidentialProperty has 1 Landlord
    [ForeignKey("UserId")]
    public int UserId { get; set; }
    public virtual UserProfile UserProfile { get; set; }
}

Landlord 可以有很多 ResidentialProperties，所以关联是一对多的。我正在尝试使用 Seed() 方法将测试数据添加到我的数据库中。我的问题是我不知道如何在方法中定义关系的多端。以下是我尝试过的:

var residentialProperties = new List<ResidentialProperty>
{
    // Property 1 associated with LandLord 1
    new ResidentialProperty { /* properties */ },
    // ...
 }

var landlords = new List<Landlord>
 {
    new Landlord { /* properties */ ResidentialProperties = residentialProperties.FirstOrDefault(x => x.ResidentialPropertyId == 1) },
    // ...
 }

ResidentialProperties = residentialProperties.FirstOrDefault(x => x.ResidentialPropertyId == 1) 给出“无法将类型 ResidentialProperty 隐式转换为 ICollection 错误。

如何在 Seed() 方法中实现一对多关系？

编辑:

我在我的上下文类中添加了以下内容来尝试实现这种类型的关系:一个房东可以有很多 ResidentialProperties。 ResidentialProperty 只能有一个房东:

modelBuilder.Entity<Landlord>()
            .HasMany(x => x.ResidentialProperties)
            .WithRequired()
            .HasForeignKey(x => x.ResidentialPropertyId);

modelBuilder.Entity<ResidentialProperty>()
            .HasRequired(x => x.UserProfile);

我仍然收到此错误:

\tSystem.Data.Entity.Edm.EdmAssociationEnd: : Multiplicity is not valid in Role 'Landlord_ResidentialProperties_Target' in relationship 'Landlord_ResidentialProperties'. Because the Dependent Role refers to the key properties, the upper bound of the multiplicity of the Dependent Role must be '1'..

仍然不知道我做错了什么。

Answer 1

您需要返回 ResidentalProperties 列表。您的查询 ResidentialProperties = residentialProperties.FirstOrDefault(x => x.ResidentialPropertyId == 1) 仅返回一个 ResidentialProperty 实体。只需执行 ResidentialProperties = residentialProperties

编辑:您可以通过单个配置进行多对一设置。您还必须指定外键。

            //ResidentialProperty has 1 Landlord ,
            //Landlord has many ResidentialProperties
            modelBuilder.Entity<ResidentialProperty>().HasRequired(a=> a.UserProfile)
                .WithMany(c=> c.ResidentialProperties)
                .HasForeignKey(a=> a.UserId);