EF Core 中两个抽象类之间的一对一关系

Question

我在为两个抽象类创建一对一关系时遇到问题。每个类都有一个表和鉴别器。

类是：

public abstract class ValuationBase
{
    public Guid Id { get; internal set; }
    public DateTime CreationDateTime { get; internal set; }

    public Owner Owner { get; internal set; }
}

public abstract class Valuation<TResult> : ValuationBase where TResult : ValuationResult
{
    public abstract ValuationType Type { get; }

    public abstract TResult Result { get; protected set; }
}

public class ScoringCardValuation : Valuation<ScoringCardValuationResult>
{
    .
    .
    .

    public override ScoringCardValuationResult Result { get; protected set; }

    public override ValuationType Type => ValuationType.ScoringCardValuation;
}

public class FirstChicagoValuation : Valuation<FirstChicagoValuationResult>
{
    .
    .
    .

    public override ValuationType Type => ValuationType.FirstChicagoValuation;

    public override FirstChicagoValuationResult Result { get; protected set; }
}


public abstract class ValuationResult
{
    public Guid Id { get; set; }
    public abstract ValuationType ValuationType { get; }
}

public class ScoringCardValuationResult : ValuationResult
{
    .
    .
    .

    public override ValuationType ValuationType => ValuationType.ScoringCardValuation;
}

public class FirstChicagoValuationResult : ValuationResult
{
    .
    .
    .

    public override ValuationType ValuationType => ValuationType.FirstChicagoValuation;
}

我的映射是：

public class ValuationBaseMapping : IEntityTypeConfiguration<ValuationBase>
{
    public void Configure(EntityTypeBuilder<ValuationBase> builder)
    {
        builder.HasKey(c => c.Id);

        builder.HasDiscriminator()
            .HasValue<ScoringCardValuation>(nameof(ScoringCardValuation))
            .HasValue<FirstChicagoValuation>(nameof(FirstChicagoValuation));

        builder.OwnsOne(i => i.Owner);
    }
}

public class ScoringCardValuationMapping : IEntityTypeConfiguration<ScoringCardValuation>
{
    public void Configure(EntityTypeBuilder<ScoringCardValuation> builder)
    {
        builder.HasOne(c => c.Result).WithOne().HasForeignKey<ScoringCardValuationResult>("ValuationResultId");
    }
}

public class FirstChicagoValuationMapping : IEntityTypeConfiguration<FirstChicagoValuation>
{
    public void Configure(EntityTypeBuilder<FirstChicagoValuation> builder)
    {
        .
        .
        .

        builder.HasOne(c => c.Result).WithOne().HasForeignKey<FirstChicagoValuationResult>("ValuationResultId");
    }
}


public class ValuationResultMapping : IEntityTypeConfiguration<ValuationResult>
{
    public void Configure(EntityTypeBuilder<ValuationResult> builder)
    {
        builder.HasKey(c => c.Id);

        builder.HasDiscriminator()
            .HasValue<ScoringCardValuationResult>(nameof(ScoringCardValuationResult))
            .HasValue<FirstChicagoValuationResult>(nameof(FirstChicagoValuationResult));
    }
}

现在，我的问题是当我为 ValuationResult 表添加迁移 EF 创建牵引外键时

我想在 ValuationResult 表中有一个外键。 实际上，我希望 ValuationBase 与 ValuationResult 具有一对一的关系。这意味着我只想要两张桌子。 每个评估驱动的类都必须有一个其类型在泛型中定义的 ValuationResult。

我该如何解决这个问题？

Answer 1

您已经声明了两个不同的实体关系（尽管它们都继承自同一个基础）。这就是 EF 创建两个外键的原因。

除非有一些不为人知的理由将该通用层保留在继承结构中，否则我将删除它并将结果链接放在基类上。

同样，除非有一些不为人知的理由来保留类型的枚举 (ValuationType)，否则只需使用类类型：

typeof(ScoringCardValuation);
// or on an instance:
cardValuation.GetType();

我会将实体重构为：

public abstract class ValuationBase
{
    public Guid Id { get; internal set; }
    public DateTime CreationDateTime { get; internal set; }

    public Owner Owner { get; internal set; }

    public virtual ValuationResult Result { get; internal set; }
}

public class ScoringCardValuation : ValuationBase
{
    public override ScoringCardValuationResult Result 
    { 
        get => base.Result as ScoringCardValuationResult;
        protected set => base.Result = value; 
    }
}

public class FirstChicagoValuation : Valuation<FirstChicagoValuationResult>
{
    public override FirstChicagoValuationResult Result 
    { 
        get => base.Result as FirstChicagoValuationResult;
        protected set => base.Result = value; 
    }
}

然后配置：

public class ValuationBaseMapping : IEntityTypeConfiguration<ValuationBase>
{
    public void Configure(EntityTypeBuilder<ValuationBase> builder)
    {
        builder.HasKey(c => c.Id);

        builder.HasDiscriminator()
            .HasValue<ScoringCardValuation>(nameof(ScoringCardValuation))
            .HasValue<FirstChicagoValuation>(nameof(FirstChicagoValuation));

        builder.OwnsOne(i => i.Owner);

        builder.HasOne(c => c.Result)
            .WithOne()
            .HasForeignKey<ValuationResult>("ValuationResultId");
    }
}

public class ScoringCardValuationMapping : IEntityTypeConfiguration<ScoringCardValuation>
{
    public void Configure(EntityTypeBuilder<ScoringCardValuation> builder)
    {
    }
}

public class FirstChicagoValuationMapping : IEntityTypeConfiguration<FirstChicagoValuation>
{
    public void Configure(EntityTypeBuilder<FirstChicagoValuation> builder)
    {
    }
}