实体框架核心一对多

Question

我正在尝试使用 Entity Framework Core 构建电话列表。每当我尝试运行推荐时：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 之间以及从 Member 到 Member 之间有几种关系。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，您必须通过明确映射关联来明确指示它。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");
}