.Net Core Entity Framework - 鉴别器 TPH

Question

我目前正在尝试写入从抽象基础 class 继承的 table。当我尝试这样做时，出现以下错误（ContactMethod 属性是鉴别器）：

System.Data.SqlClient.SqlException: Invalid column name 'ContactMethod'.

EmailContactDetails.cs:

public class EmailContactDetail : ContactDetail
{
    [ApiMember(Description = "The Contact Method")]
    public override ContactMethod ContactMethod => ContactMethod.Email;

    [ApiMember(Description = "Email Address")]
    public string EmailAddress { get; set; }
}

EmailContactDetailConfiguration.cs:

public class EmailContactDetailsConfiguration : IEntityTypeConfiguration<EmailContactDetail>
{
    public void Configure(EntityTypeBuilder<EmailContactDetail> builder) => Configure(builder, "dbo");

    public void Configure(EntityTypeBuilder<EmailContactDetail> builder, string schema)
    {
        builder.Property(x => x.EmailAddress).HasColumnName("EmailAddress").HasColumnType("nvarchar(255)");
    }
}

ContactDetail.cs:

public abstract class ContactDetail
{
    [ApiMember(Description = "The Identifier")]
    public Guid Id { get; set; }

    [ApiMember(Description = "The Contact Method")]
    public virtual ContactMethod ContactMethod { get; set; }
}

ContactDetailConfiguration.cs

public class ContactDetailsConfiguration : IEntityTypeConfiguration<ContactDetail>
{
    public void Configure(EntityTypeBuilder<ContactDetail> builder) => Configure(builder, "dbo");

    public void Configure(EntityTypeBuilder<ContactDetail> builder, string schema)
    {
        builder.ToTable("ContactDetails", schema);

        // Table per hierarchy. all subclasses share the same db table for performance.
        builder.HasDiscriminator(x => x.ContactMethod)
            .HasValue<EmailContactDetail>(ContactMethod.Email);

        builder.Property(x => x.Id).HasColumnName("Id").IsRequired().HasColumnType("uniqueidentifier").ValueGeneratedOnAdd();
    }
}

我尝试通过将以下内容添加到 ContactDetailConfiguration.cs 文件来隐藏鉴别器 "ContactMethod"：

builder.Ignore(x => x.ContactMethod);

完成后，出现以下错误

The entity type 'EmailContactDetail' is part of a hierarchy, but does not have a discriminator property configured.

Answer 1

您不应向 EF 隐藏配置为 TPH 鉴别器的属性，因为它对于 EF Core 实施 TPH 策略至关重要。

初始错误仅表示您的模型和数据库不同步。的确，按照惯例，EF Core 使用 string shadow property 和名为 Discriminator 的列。但是 HasDiscriminator fluent API 的全部目的是允许更改鉴别器 property/column 类型，以及将其映射到实体模型的现有属性。

这里是这样的。您已告知 EF Core 使用现有属性 ContactMethod 作为鉴别器，因此 EF Core 正在数据库 table 中查找名为 ContactMethod 的列。因此，要解决此问题，只需从模型更新数据库（在更改模型时使用通常的过程 - 添加新迁移、更新数据库等）。

.Net Core Entity Framework - 鉴别器 TPH

.Net Core Entity Framework - Discrimator TPH

c#

entity-framework-core

ef-fluent-api

.net-core