Entity Framework 核心一对多

Question

我正在尝试使用 Entity Framework 核心构建一个 phone 列表。每当我尝试 运行 表扬时：Add-Migration "Initial"

我收到以下错误：Unable to determine the relationship represented by navigation property 'Member.MemberTeam' of type 'Team'. Either manually configure the relationship, or ignore this property from the model.

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Member和Member之间存在多种关系。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。可以理解为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，还是除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");
}