如何建立具有多种原则的'拥有'数据库关系？

Question

在代码中我有一个对象图，看起来像这样：

public class Author 
{ 
    public int AuthorId { get; set; } 
    public string Name { get; set; } 
    public Address Address { get; set; } 
} 

public class Publisher 
{ 
    public int PublisherId { get; set; } 
    public string Name { get; set; } 
    public Address Address { get; set; } 
} 

public class Address 
{ 
    public int AddressId { get; set; } 
    public string Postcode { get; set; } 
} 

如何在关系数据库模式的模型呢？

这需要是0-1..1的关系，即作者和发布者可能有或没有地址。

理想情况地址必须由作者或发布者引用，但不能同时引用。

如果您可以使用导航属性在实体框架核心中对其进行建模，并且级联删除删除作者或发布者时删除地址，则可以获得巨大的奖励。 （但我敢打赌，没有人能够）。

我列出了所有我尝试过的东西，但是这个帖子太久没有人会阅读它了。只是说我已经尝试了所有我能想到的事情就会更快。

Answer 1

您有很多方法可以在EF Core中实现目标。关键的一点是，Address将是关系的依赖结束，它将包含可选 FKS到主要实体Author和Publisher。

这里是可能Address型号和配置：

（1）Address具有明确FK和导航属性

型号：

public class Address 
{ 
    public int AddressId { get; set; } 
    public string Postcode { get; set; } 

    public int? AuthorId { get; set; } 
    public Author Author { get; set; } 

    public int? PublisherId { get; set; } 
    public Publisher Publisher { get; set; } 
} 

配置：

modelBuilder.Entity<Author>() 
    .HasOne(e => e.Address) 
    .WithOne(e => e.Author) 
    .HasForeignKey<Address>(e => e.AuthorId) 
    .OnDelete(DeleteBehavior.Cascade); 

modelBuilder.Entity<Publisher>() 
    .HasOne(e => e.Address) 
    .WithOne(e => e.Publisher) 
    .HasForeignKey<Address>(e => e.PublisherId) 
    .OnDelete(DeleteBehavior.Cascade); 

（2）与Address导航属性仅

型号：

public class Address 
{ 
    public int AddressId { get; set; } 
    public string Postcode { get; set; } 

    public Author Author { get; set; } 

    public Publisher Publisher { get; set; } 
} 

配置：

modelBuilder.Entity<Author>() 
    .HasOne(e => e.Address) 
    .WithOne(e => e.Author) 
    .HasForeignKey<Address>("AuthorId") 
    .OnDelete(DeleteBehavior.Cascade); 

modelBuilder.Entity<Publisher>() 
    .HasOne(e => e.Address) 
    .WithOne(e => e.Publisher) 
    .HasForeignKey<Address>("PublisherId") 
    .OnDelete(DeleteBehavior.Cascade); 

（3）Address具有明确FK属性仅

型号：

public class Address 
{ 
    public int AddressId { get; set; } 
    public string Postcode { get; set; } 

    public int? AuthorId { get; set; } 

    public int? PublisherId { get; set; } 
} 

配置：

modelBuilder.Entity<Author>() 
    .HasOne(e => e.Address) 
    .WithOne() 
    .HasForeignKey<Address>(e => e.AuthorId) 
    .OnDelete(DeleteBehavior.Cascade); 

modelBuilder.Entity<Publisher>() 
    .HasOne(e => e.Address) 
    .WithOne() 
    .HasForeignKey<Address>(e => e.PublisherId) 
    .OnDelete(DeleteBehavior.Cascade); 

（4）Address没有明确FK和导航属性

型号：

public class Address 
{ 
    public int AddressId { get; set; } 
    public string Postcode { get; set; } 
} 

配置：

modelBuilder.Entity<Author>() 
    .HasOne(e => e.Address) 
    .WithOne() 
    .HasForeignKey<Address>("AuthorId") 
    .OnDelete(DeleteBehavior.Cascade); 

modelBuilder.Entity<Publisher>() 
    .HasOne(e => e.Address) 
    .WithOne() 
    .HasForeignKey<Address>("PublisherId") 
    .OnDelete(DeleteBehavior.Cascade); 

参考：Relationships