是否可以在没有外键的情况下设置导航属性？

Question

是否可以有两个（或多个）相同类型的导航属性？

我的模型看起来像这样......

public class Agreement
{
    public int Id { get; set; }
    public Guid? BuyerId { get; set; }
    public Guid? SellerId { get; set; }

    public AgreementInfo ByerAgreementInfo { get; set; }
    public AgreementInfo SellerAgreementInfo { get; set; }
}

public class AgreementInfo
{
    // PK is AgreementId and OwnerActorId combined.
    public int AgreementId { get; set; }
    public Guid OwnerActorId { get; set; }
    public string Name { get; set; }
}

...我试图通过匹配AgreementId和ByerId/SellerId来包含导航属性...

modelBuilder.Entity<Agreement>().HasOne(x => x.ByerAgreementInfo).WithOne().HasForeignKey<Agreement>(x => new {x.Id, x.ProviderId});
modelBuilder.Entity<Agreement>().HasOne(x => x.SellerAgreementInfo).WithOne().HasForeignKey<Agreement>(x => new { x.Id, x.RequesterId });

...但这会导致循环依赖。

有没有办法在不使用外键的情况下包含这些属性？ 或者是否有另一种解决方案（除了向信息表添加一个 id 列）允许我使用信息表行作为协议类中的导航属性？

Answer 1

有很多方法可以实现您想要的。 您可以在您的子项上使用具有InverseProperty属性的数据注释，在您的父项上使用ForeignKey属性，或者在模型构建器中以任何一种方式使用流畅的语法。 我倾向于尽可能使用属性（数据注释）（这只是我个人的喜好），我发现它需要查看实际模式本身中的关系（尽管其他人可能不会）。

使用ForeignKey属性：

public class Agreement
{
    ...

    [ForeignKey("ByerAgreementInfo ")]
    public int ByerAgreementInfoId { get; set; }
    public AgreementInfo ByerAgreementInfo { get; set; }

    [ForeignKey("SellerAgreementInfo ")]
    public int SellerAgreementInfoId { get; set; }
    public AgreementInfo SellerAgreementInfo { get; set; 
}

使用InverseProperty属性：

public class AgreementInfo
{

    ...

    [InverseProperty("ByerAgreementInfo ")]
    public ICollection<Agreement> Sellers { get; set; }
    [InverseProperty("SellerAgreementInfo ")]
    public ICollection<Agreement> Buyers { get; set; }
}

如果您想使用Fluent Syntax ，我相信以下方法会起作用（尽管我已经有一段时间没有使用它了）：

modelBuilder.Entity<Agreement>()
    .HasOne(x => x.ByerAgreementInfo)
    .WithOne()
    .HasForeignKey<Agreement>(p => p.ByerAgreementInfoId);

modelBuilder.Entity<Agreement>()
    .HasOne(x => x.SellerAgreementInfo)
    .WithOne()
    .HasForeignKey<Agreement>(p => p.SellerAgreementInfoId);

_{注意：我认为您可能需要模型中的实际 Id，但我不记得了。}

Answer 2

...但这会导致循环依赖

是的！ 它会。 要克服这个问题，您必须指定.OnDelete(DeleteBehavior.Restrict); 在您的Fluent API配置中，如下所示，但首先您也必须按如下方式编写您的Agreement模型类：

public class Agreement
{
    public int Id { get; set; }
    public Guid? BuyerId { get; set; }
    public Guid? SellerId { get; set; }

    public int AgreementIdForBuyer { get; set; }
    public Guid OwnerActorIdForBuyer { get; set; }

    public int AgreementIdForSeller { get; set; }
    public Guid OwnerActorIdForSeller { get; set; }

    public AgreementInfo ByerAgreementInfo { get; set; }
    public AgreementInfo SellerAgreementInfo { get; set; }
}

现在在Fluent API配置中：

modelBuilder.Entity<Agreement>()
    .HasOne(x => x.ByerAgreementInfo)
    .WithOne()
    .HasForeignKey<Agreement>(p => new {p.AgreementIdForBuyer, p.AgreementIdForBuyer})
    .OnDelete(DeleteBehavior.Restrict); // <-- Here it is

modelBuilder.Entity<Agreement>()
    .HasOne(x => x.SellerAgreementInfo)
    .WithOne()
    .HasForeignKey<Agreement>(p => new {p.AgreementIdForSeller, p.OwnerActorIdForSeller})
    .OnDelete(DeleteBehavior.Restrict); // <-- Here it is