首先将外键映射到EF代码中的非主代理键列 [英] Mapping foreign key to non primary surrogate key column in EF code first

问题描述

public class A    
{   
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public virtual int Aid { get; set; }    

    public virtual ICollection<B> B { get; set; }    
}


public class B
{    
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]     
    public virtual int Bid { get; set; }

    [Key]
    [Column(Order = 0)]
    [Required]           
    Public virtual string BName {get ; set}

    [Key]
    [Column(Order = 1)]
    [Required]      
    public virtual int Aid { get; set; }

    [ForeignKey("Aid")]
    public virtual  A A { get; set; }

    public virtual ICollection<C> C { get; set; }    
}


public class C
{
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]     
    public virtual int Cid { get; set; }

    [Key]
    [Column(Order = 0)]
    [Required]    
    Public virtual string CName {get ; set}    

    [Key]
    [Column(Order = 1)]
    [Required]          
    public virtual int Bid { get; set; }

     [ForeignKey("Bid")]
     public virtual  B B { get; set; } 
}

B和C之间的关系困扰着我。我不想包括BName作为C类中的外键

relationship between B and C is troubling me .I dont want to include BName as foreign key in Class C

错误：在关系约束中，从属角色和主体角色
的属性数必须为相同

Error : The number of properties in the Dependent and Principal Roles in a relationship constraint must be identical

我理解错误，但是我只想通过Bid指向C类，如何在不干扰两者之间关系的情况下实现它A和B。

I understand the error but I want to point to C class only by Bid ,how I can achieve it without disturbing the relationship between A and B.

推荐答案

该问题被标记为EF6。但是，如果您找到此搜索EF Core。可以使用备用键。

This question is tagged for EF6. But if you find this searching for EF Core. Can use Alternate Keys.

来自链接：

备用键可用作关系的目标。

Alternate keys can be used as the target of a relationship.

class MyContext : DbContext
{
    public DbSet<Blog> Blogs { get; set; }
    public DbSet<Post> Posts { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Post>()
            .HasOne(p => p.Blog)
            .WithMany(b => b.Posts)
            .HasForeignKey(p => p.BlogUrl)
            .HasPrincipalKey(b => b.Url);
    }
}

public class Blog
{
    public int BlogId { get; set; }
    public string Url { get; set; }

    public List<Post> Posts { get; set; }
}

public class Post
{
    public int PostId { get; set; }
    public string Title { get; set; }
    public string Content { get; set; }

    public string BlogUrl { get; set; }
    public Blog Blog { get; set; }
}

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