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.

以下是我的模特：

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以及Member到Member之间存在多种关系。如果你只有这个型号......

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结束，还是除了一对多关联之外的新关联。但是，EF不会为您选择，您必须明确地通过映射关联来明确指示它。例如（在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");
}

实体框架核心一对多

1 个答案: