Ef 核心，具有不同数据类型的多对多连接表复合键

Question

如何确保具有不同数据类型的两个属性的组合键？EF Core 抱怨说;

从具有外键属性 {'UserId' ： string} 的 'GroupUsers.Groups' 到 'Group.GroupUsers' 的关系不能以主键 {'GroupId' ： int} 为目标，因为它不兼容。为此关系配置一个主键或一组兼容的外键属性。

我的表是与主键的多对多关系，其类型不同，如下所示

public class Group
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int GroupId { get; set; }
    [Required]
    public string GroupName { get; set; }
    public ICollection<GroupUsers> GroupUsers { get; set; }
}
public class User
{
    [Key]
    public string UserId { get; set; }
    public string Email { get; set; }
    public ICollection<GroupUsers> GroupUsers { get; set; }
}
public class GroupUsers
{
    public string UserId { get; set; }
    public int GroupId { get; set; }
    [ForeignKey("GroupId")]
    public Group Groups { get; set; }
    [ForeignKey("UserId")]
    public User Users { get; set; }
}

这是我忘了展示的流利的一面

     modelBuilder.Entity<GroupUsers>().HasKey(gu => new { gu.GroupId, gu.UserId});
     modelBuilder.Entity<GroupUsers>().HasOne(ub => ub.Users)
            .WithMany(x => x.GroupUsers).HasForeignKey(h => h.GroupId)
            .OnDelete(DeleteBehavior.SetNull);
      modelBuilder.Entity<GroupUsers>().HasOne(ub => ub.Groups)
            .WithMany(x => x.GroupUsers).HasForeignKey(h => h.UserId)
            .OnDelete(DeleteBehavior.Cascade);

Answer 1

看到您的流畅配置后，您的HasForeignKey呼叫似乎已切换。

它应该是：

modelBuilder.Entity<GroupUsers>().HasKey(gu => new { gu.GroupId, gu.UserId});
modelBuilder.Entity<GroupUsers>().HasOne(ub => ub.Users)
    .WithMany(x => x.GroupUsers).HasForeignKey(h => h.UserId)  // <-- change to this
    .OnDelete(DeleteBehavior.SetNull);
modelBuilder.Entity<GroupUsers>().HasOne(ub => ub.Groups)
    .WithMany(x => x.GroupUsers).HasForeignKey(h => h.GroupId)  // <-- change to this
    .OnDelete(DeleteBehavior.Cascade);