c# - Entity Framework 核心一对多

Question

我正在尝试使用 Entity Framework Core 构建电话列表。每当我尝试运行命令时:Add-Migration "Initial"

我收到以下错误:无法确定由“团队”类型的导航属性“Member.MemberTeam”表示的关系。手动配置关系，或从模型中忽略此属性。

这是我的模型:

public class Member {
        public int Id { get; set; }
        public string MemberName { get; set; }
        public string MemberTitle { get; set; }
        public Member MemberSupervisor { get; set; }
        public Team MemberTeam { get; set; }
    }

public class Team {
    public int Id { get; set; }
    public string TeamName { get; set; }
    public Member TeamSupervisor { get; set; }
    public ICollection<Member> TeamMembers { get; set; }
}

有什么建议吗？

Answer 1

Team 和Member 之间以及从Member 到Member 之间有多种关系。如果你只有这个模型......

public class Member
{
    public int Id { get; set; }
    public string MemberName { get; set; }
    public string MemberTitle { get; set; }
    public Team MemberTeam { get; set; }
}
public class Team
{
    public int Id { get; set; }
    public string TeamName { get; set; }
    public ICollection<Member> TeamMembers { get; set; }
}

... EF 不需要任何帮助。它会理解 Team.TeamMembers 和 Member.MemberTeam 是一个关联的两端。

现在如果你只添加...

public Member TeamSupervisor { get; set; }

... EF 必须选择这是与 MemberTeam 的一对一关联的反向端，还是一对多关联之外的新关联。但是，EF 不会为您选择，您必须通过显式映射关联来明确地指示它。例如(在您的 DbContext 子类中):

protected override void OnModelCreating(ModelBuilder mb)
{
    mb.Entity<Team>().Property(a => a.Id).UseSqlServerIdentityColumn();
    mb.Entity<Team>().HasMany(t => t.TeamMembers).WithOne(m => m.MemberTeam);
    mb.Entity<Team>().HasOne(t => t.TeamSupervisor).WithMany()
                     .HasForeignKey("SupervisorId");

    mb.Entity<Member>().Property(a => a.Id).UseSqlServerIdentityColumn();
    mb.Entity<Member>().HasOne(m => m.MemberSupervisor).WithMany()
                       .HasForeignKey("SupervisorId");
}