自参照许多一对多的关系

Question

我有一个Ticket实体：

public class Ticket 
    { 
     public int Id { get; set; } 
     public string Title { get; set; } 

     public virtual ICollection<Relation> RelatedTickets { get; set; } 
    } 

我想设置实体框架中的核心多到很多自我的关系，所以我做了两个一到多关系：

public class Relation 
{ 
    [Required, ForeignKey("TicketFrom")] 
    public int FromId { get; set; } 

    [Required, ForeignKey("TicketTo")] 
    public int ToId { get; set; } 

    public virtual Ticket TicketFrom { get; set; } 
    public virtual Ticket TicketTo { get; set; } 
} 

我试图用建立的关系流利的API：

 builder.Entity<Relation>() 
       .HasKey(uc => new { uc.FromId, uc.ToId }); 
     builder.Entity<Relation>() 
      .HasOne(c => c.TicketFrom) 
      .WithMany(p => p.RelatedTickets) 
      .HasForeignKey(pc => pc.FromId); 
     builder.Entity<Relation>() 
      .HasOne(c => c.TicketTo) 
      .WithMany(p => p.RelatedTickets) 
      .HasForeignKey(pc => pc.ToId); 

但结果我有一个错误：

Cannot create a relationship between 'Ticket.RelatedTickets' and 'Relation.TicketTo', because there already is a relationship between 'Ticket.RelatedTickets' and 'Relation.TicketForm'. Navigation properties can only participate in a single relationship.

可能的解决方案是直接添加父关系TicketEntity：

public class Ticket 
{ 
    public int Id { get; set; } 

    [Required, ForeignKey("ParentRelation")] 
    public Nullable<int> ParentRelationId { get; set; } 

    public virtual Ticket ParentRelation {get;set;} 

    public virtual ICollection<Ticket> RelatedTickets { get; set; } 
    ... 
} 

用流利的API是这样的：

modelBuilder.Entity<Ticket> => 
{ 
    entity 
     .HasMany(e => e.RelatedTickets) 
     .WithOne(e => e.ParentRelation) 
     .HasForeignKey(e => e.ParentRelationId); 
}); 

但它看起来 '脏' 到存储这样的父母关系。
什么是正确的方法？

Answer 1

不可能只有一个关系集合。您需要两张关系票等于TicketFrom，第二张关票等于TicketTo。

事情是这样的：

型号：

public class Ticket 
{ 
    public int Id { get; set; } 
    public string Title { get; set; } 

    public virtual ICollection<Relation> RelatedTo { get; set; } 
    public virtual ICollection<Relation> RelatedFrom { get; set; } 
} 

public class Relation 
{ 
    public int FromId { get; set; } 
    public int ToId { get; set; } 

    public virtual Ticket TicketFrom { get; set; } 
    public virtual Ticket TicketTo { get; set; } 
} 

配置：

modelBuilder.Entity<Relation>() 
    .HasKey(e => new { e.FromId, e.ToId }); 

modelBuilder.Entity<Relation>() 
    .HasOne(e => e.TicketFrom) 
    .WithMany(e => e.RelatedTo) 
    .HasForeignKey(e => e.FromId); 

modelBuilder.Entity<Relation>() 
    .HasOne(e => e.TicketTo) 
    .WithMany(e => e.RelatedFrom) 
    .HasForeignKey(e => e.ToId); 

注意，使用母公司的解决方案是不等价的，因为它会创建one-to-many协会，如果我理解正确，你正在寻找为many-to-many。