c# - 如何在 Entity Framework 中设置两个一对多关系？

Question

假设我们正在使用 Entity Framework 代码优先方法，并且我们有两个对象，它们通过两个一对多关系链接(一个 Person 可以拥有多个 Car ，但每辆车都有一个车主和一个“主要司机”)。这是两个实体:

public class Person {
    #region Persisted fields
    [Required]
    public int PersonId { get; set; }
    [Required]
    public string FirstName { get; set; }
    [Required]
    public string Surname { get; set; }
    #endregion

    #region Navigation properties
    public virtual ICollection<Car> CarsOwned { get; set; }
    #endregion
}

public class Car {
    #region Persisted fields
    [Required]
    public int CarId { get; set; }
    [Required]
    public string Make { get; set; }
    [Required]
    public string Manufacturer { get; set; }
    [Required]
    public string RegNo { get; set; }
    [Required]
    [ForeignKey("Owner")]
    public int OwnerId { get; set; }
    [Required]
    [ForeignKey("MainDriver")]
    public int MainDriverId { get; set; }
    #endregion

    #region Navigation properties
    public virtual Person Owner { get; set; }
    public virtual Person MainDriver { get; set; }
    #endregion
}

我如何告诉 Entity Framework 应该使用两个外键(OwnerId 或 MainDriverId)中的哪一个来确定 CarsOwned 集合？我只是尝试用这两个实体自动创建一个数据库，它假设我出于某种原因想使用 MainDriverId 作为 CarsOwned 外键，而显然我想使用 OwnerId 外键。

Answer 1

我怀疑您必须使用流畅的配置来进行设置。

public class YourContext : DbContext
{
   ...
   protected override OnModelCreating(DbModelBuilder modelBuilder)
   {
      modelBuilder.Entity<Car>()
         .HasRequired(c => c.Owner)
         .WithMany(p => p.CarsOwned)
         .HasForeignKey(c => c.OwnerId)
         .WillCascadeOnDelete(false);
          // Otherwise you might get a "cascade causes cycles" error

      modelBuilder.Entity<Car>()
         .HasRequired(c => c.MainDriver)
         .WithMany() // No reverse navigation property
         .HasForeignKey(c => c.MainDriverId)
         .WillCascadeOnDelete(false);
   }
}