c# - 如何基于自定义属性添加一对多关系

Question

假设我有两个实体:

public class Customer
{
     public int CustomerId { get; set; }
     public Guid CustomerKey { get; set; }

     public ICollection<Product> Products { get; set; }
}

public class Product
{
     public int ProductId { get; set; }
     public Guid CustomerKey { get; set; }
     public string Name { get; set; }
}

1 个客户可以拥有许多产品，但我想根据 CustomerKey 属性绑定(bind)它们。以下是示例数据的示例:

CustomerId | CustomerKey
    1      | {00000000-0000-0000-0000-111111111111}
    2      | {00000000-0000-0000-0000-222222222222}

ProductId  | Name     | CustomerKey
    1      | Product1 | {00000000-0000-0000-0000-111111111111}
    2      | Product2 | {00000000-0000-0000-0000-111111111111}
    3      | Product3 | {00000000-0000-0000-0000-222222222222}

因此，第一个客户拥有前两种产品，第二个客户拥有最后一个产品。我尝试做类似的事情:

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<Customer>().HasMany(m => m.Products);
}

但是我如何指定要将它们绑定(bind)到 CustomerKey 上？

Answer 1

这是可能的，但前提是 Customer 的 CustomerKey 属性(列)是唯一的。这是EF Core的要求(实际上是关系数据库FK要求，但EF Core仅支持可以表示为关系数据库FK约束的关系)，所以如果不是，那么您所要求的就是不可能的。

流畅的 API 是 HasPrincipalKey方法:

Configures the unique property(s) that this relationship targets. Typically you would only call this method if you want to use a property(s) other than the primary key as the principal property(s). If the specified property(s) is not already a unique constraint (or the primary key) then a new unique constraint will be introduced.

当然，FK 照常配置为 HasForeignKey .

将其应用到您的模型:

modelBuilder.Entity<Customer>()
    .HasMany(customer => customer.Products)
    .WithOne() // no navigation property
    .HasForeignKey(product => product.CustomerKey)
    .HasPrincipalKey(customer => customer.CustomerKey);