Ef Core，多对多连接 table 具有不同数据类型的复合键

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；

从'GroupUsers.Groups'到'Group.GroupUsers'具有外键属性{'UserId' : string}的关系不能以主键{[=为目标28=] : int} 因为它不兼容。为此关系配置主键或一组兼容的外键属性。

我的表是多对多关系，主键的类型不同，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; }
}

这是我忘记展示的 Fluent 方面

     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

看了你流畅的配置，看来你的HasForeignKey调用被切换了。

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);

Ef Core，多对多连接 table 具有不同数据类型的复合键

Ef Core, many-to-many connection table composite key with different datatypes

c#

entity-framework-core

ef-fluent-api