EF6一对多和一对一相同实体之间 [英] EF6 One to Many and Many to One between same entities

问题描述

我正在尝试创造双重关系。让我们说一个团队和玩家 - 一个团队有很多玩家，但只有一个队长。

  public class Team 
 {
 public int Id {get;组; } 
 public virtual ICollection< Player>玩家{get;组; } 
 
 public Player Captain {get;组; } 
 public int CaptainId {get;组; } 
} 
 
 
 public class Player 
 {
 public int Id {get;组; } 
 public string Name {get;组; } 
 
 [InverseProperty（Players）] 
 public virtual Team Team {get;组; } 
 public int TeamId {get;组; } 
} 
  

当运行update-database时，会导致沿着
ALTER TABLE语句与FOREIGN KEY约束FK_dbo.Teams_dbo.Players_TeamId冲突。冲突发生在数据库dev，表dbo.Players，列Id。 （我正在从我真正的类名/字段翻译）

解决方案

使用Fluent API明确描述您的实体关系。 >

  modelBuilder.Entity< Team>（）。HasMany（t => t.Players）.WithRequired（p => p.Team ）.HasForeignKey（p => p.TeamId）; 
 modelBuilder.Entity< Team>（）。HasRequired（t => t.Captain）.WithMany（）。HasForeignKey（t => t.CaptainId）; 
  

您可以在上面看到Team-> Captain关系被视为一对一。大概一个给定的球员不能是不止一个队伍的队长，但是由于Team-> Player的关系是一对多的，所以一个给定的球员不在一个队伍上，而且应该很容易确保你的用户界面，一个团队的队长也是该队的一名球员，因此一名给定的球员只能是一队的队长。

I'm trying to create a double relationship. Lets say its a Team and Players - a Team has many Players but only one captain

    public class Team
    {
        public int Id { get; set; }
        public virtual ICollection<Player> Players { get; set; }

        public Player Captain { get; set; }
        public int CaptainId { get; set; }
    }


    public class Player
    {
        public int Id { get; set; }
        public string Name { get; set; }

        [InverseProperty("Players")]
        public virtual Team Team { get; set; }
        public int TeamId { get; set; }
    }

When running update-database this is resulting in an error along the lines of The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK_dbo.Teams_dbo.Players_TeamId". The conflict occurred in database "dev", table "dbo.Players", column 'Id'. (I'm translating from my real classnames/fields)

解决方案

Explicitly describe your entity relationship using the Fluent API.

modelBuilder.Entity<Team>().HasMany(t => t.Players).WithRequired(p => p.Team).HasForeignKey(p => p.TeamId);
modelBuilder.Entity<Team>().HasRequired(t => t.Captain).WithMany().HasForeignKey(t => t.CaptainId);

You can see above that the Team->Captain relationship is treated as a many-to-one. Presumably a given player can't be captain of more than one team, but since the Team->Player relationship is one-to-many, a given player isn't on more than one team anyway and it should be easy to ensure through your UI that a team's captain is also a player for that team and thus a given player will only be captain for one team.

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