多对多自参考

Question

一个用户可以管理多个公司。并且用户可以从多公司列表中一次拥有一个活跃的公司。我怎么能做到这一点？

我目前的模型是：

public class User

{

    public int Id

    public virtual ICollection<Company> Companies { get; set; }

    public User()

    {

        this.Companies = new HashSet<Company>();

    }

}

public class Company

{

    public int Id

    public virtual ICollection<User> Users { get; set; }

    public User()

    {

        this.Users = new HashSet<User>();

    }

}

如果我添加另一个注释：

public class User

{

    public int CompanyId

    public virtual Company Company { get; set; }

}

该模型不会引用多对多表哪个UserCompany表。

我怎么能做到这一点？或者这种情况有另一种方法吗？

现在我正在考虑制作手动多对多关系模型并添加ActiveCompany从自定义多对多关系引用的另一个字段。这是好方法吗？

Answer 1

我很确定你可以通过使用 fluent api 并覆盖OnModelCreating你的 中的方法来做到这一点DbContext，但我没有手头的例子。但是，您可能会发现为您的用户添加另一个属性更容易public int ActiveCompanyId { get; set; }有很多变量，例如您是否使用延迟加载、有多少公司/用户、您的数据访问模式是什么，这可能决定您的最佳整体方法。如果您的Companies属性通常或总是被填充，那么您可以创建一个get未映射的唯一属性：public class User{&nbsp; &nbsp; public int Id&nbsp; &nbsp; public virtual ICollection<Company> Companies { get; set; }&nbsp; &nbsp; public int ActiveCompanyId { get; set; }&nbsp; &nbsp; [NotMapped]&nbsp; &nbsp; public Company ActiveCompany&nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; get&nbsp; &nbsp; &nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; return this.Companys == null ? null :&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Companies.Where(x => x.Id == this.Active.CompanyId)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;.SingleOrDefault;&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; }&nbsp; &nbsp; public User()&nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp;this.Companies = new HashSet<Company>();&nbsp; &nbsp; }}

Answer 2

你能试试这个映射吗：protected override void OnModelCreating(DbModelBuilder modelBuilder){&nbsp; &nbsp; modelBuilder.Entity<Company>()&nbsp; &nbsp; &nbsp; &nbsp; .HasMany(c => c.Users)&nbsp; &nbsp; &nbsp; &nbsp; .WithMany(u => u.Comapnies)&nbsp; &nbsp; &nbsp; &nbsp; .Map(x =>&nbsp; &nbsp; &nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; x.MapLeftKey("CompanyId");&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; x.MapRightKey("UserId");&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; x.ToTable("UserCompany");&nbsp; &nbsp; &nbsp; &nbsp; });&nbsp; &nbsp; modelBuilder.Entity<User>()&nbsp; &nbsp; &nbsp; &nbsp; .HasRequired(b => b.Company)&nbsp; &nbsp; &nbsp; &nbsp; .WithMany()&nbsp; &nbsp; &nbsp; &nbsp; .WillCascadeOnDelete(false);}