entity-framework - EF6 Code First - 可能导致循环或多个级联路径

Question

我首先使用 EF6 代码。
我有两个类(class):

public class Player
{
    [DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
    [Key]
    public int Id { get; set; }

    [Required, MinLength(2, ErrorMessage = "Player name must be at least 2 characters length")]
    public string Name { get; set; }

    [Required]
    public int TeamClubId { get; set; }

    [Required]
    public int TeamNationalId { get; set; }

    [Required, ForeignKey("TeamClubId")]
    public virtual Team Club { get; set; }

    [Required, ForeignKey("TeamNationalId")]
    public virtual Team National { get; set; }

}

和:

 public class Team
{
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }

    [Required, MinLength(2, ErrorMessage = "Team name must be at least 2 characters length")]
    public string Name { get; set; }

    [Required]
    public TeamType Type { get; set; }

    public virtual ICollection<Player> Players { get; set; }
}

这是我的两个类与他们的关系。
一名球员属于两支球队:俱乐部和国家队。
一支球队可以是俱乐部的，也可以是国家队的，并且拥有一批球员。

在我的上下文文件中，我使用:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Player>()
                .HasRequired<Team>(p => p.National)
                .WithMany(t => t.Players)
                .WillCascadeOnDelete(false);

        base.OnModelCreating(modelBuilder);
    }

运行迁移工具更新数据库时，出现以下错误:

在表 'Players' 上引入 FOREIGN KEY 约束 'FK_dbo.Players_dbo.Teams_TeamNationalId' 可能会导致循环或多个级联路径。指定 ON DELETE NO ACTION 或 ON UPDATE NO ACTION，或修改其他 FOREIGN KEY 约束。
无法创建约束。请参阅以前的错误。

我该如何解决？

Answer 1

使用 Fluent API:

        //player - national team relations
        modelBuilder.Entity<Player>()
            .HasRequired<Team>(p => p.National)
            .WithMany()
            .WillCascadeOnDelete(false);

        //player - club team relations
        modelBuilder.Entity<Player>()
            .HasRequired<Team>(p => p.Club)
            .WithMany()
            .WillCascadeOnDelete(false);