Question

我目前正在尝试写入一个继承自抽象基类的表。当我尝试这样做时，我得到以下错误（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();
    }
}

我试图隐藏鉴别器＆＃34; ContactMethod＆＃34;通过将以下内容添加到ContactDetailConfiguration.cs文件：

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

一旦我完成了，我最终会遇到以下错误

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

Answer 1

您不应该隐藏从EF配置为TPH鉴别器的属性，因为它对于EF Core策略的EF Core实施至关重要。

初始错误只表示您的模型和数据库不同步。按惯例，EF Core使用string shadow property和名为Discriminator的列。但HasDiscriminator流畅API的全部目的是允许更改discriminator属性/列类型，以及将其映射到实体模型的现有属性。

这是这种情况。您已告知EF Core使用现有属性ContactMethod作为鉴别器，因此EF Core正在数据库表中查找名为ContactMethod的列。因此，要解决此问题，只需从模型更新数据库（使用模型更改时的常规过程 - 添加新迁移，更新数据库等）。

.Net核心实体框架 - Discrimator TPH

1 个答案: