Csharp 具有单一导航属性的EF核心一对多关系

格特·阿诺德是正确的.在阅读了他们提供的链接并更好地查看了我的用例之后，我确实需要使用每个层次 struct 的表和鉴别器多态关系.我不能张贴我的确切代码，因为它是为了工作.但我确实改变了上面的例子，以包含我所做的事情.

长话短说.我需要创建我的基本实体的两个子类，并将每个子类的属性添加到父类.我还需要配置EFCore，使其知道将使用单个DB表来保存两个不同类的数据.

  [Table("parent")]
  public class Parent
  {
      [Key]
      [Column("parentid")]
      public long ParentId { get; set; }

      [Column("name")]
      public string Name { get; set; }

      // The following properties are of different class but their data is stored in
      // the same DB table.
      public Son Son { get; set; }

      public Daughter Daughter { get; set; }
  }

  public enum Gender
  {
      Male,
      Female
  }

  // Base class must be marked as abstract or another call to .HasValue on the DB context needs to be made.
  [Table("child")]
  public abstract class Child
  {
      [Key]
      [Column("childid")]
      public long ChildId { get; set; }

      public Gender Gender { get; set; }

      [Column("name")]
      public string Name { get; set; }

      public List<Grandchild1> Grandchildren1 { get; set; }

      public List<Grandchild2> Grandchildren2 { get; set; }

      public List<Grandchild3> Grandchildren3 { get; set; }
  }

  public class Son : Child
  {

  }

  public class Daughter : Child
  {

  }

  [Table("grandchild1")]
  public class Grandchild1
  {
      [Key]
      [Column("grandchildid")]
      public long ChildId { get; set; }
  }

  [Table("grandchild2")]
  public class Grandchild2
  {
      [Key]
      [Column("grandchildid")]
      public long ChildId { get; set; }
  }

  [Table("grandchild3")]
  public class Grandchild3
  {
      [Key]
      [Column("grandchildid")]
      public long ChildId { get; set; }
  }

  public class FamilyDbContext : DbContext
  {
      protected override void OnModelCreating(ModelBuilder builder)
      {
          // This call tells EFCore that the Child entity will contain a column (Gender)
          // that is used to determine if a given record in the DB maps to either a
          // Son or Daughter class based on the value.
          builder.Entity<Child>(c =>
          {
              c.HasDiscriminator(c => c.Gender)
              .HasValue<Son>(Gender.Male)
              .HasValue<Daughter>(Gender.Female);
          });
      }

      public DbSet<Parent> Parents { get; set; }

      public DbSet<Child> Children { get; set; }

      public DbSet<Grandchild1> Grandchildren1 { get; set; }

      public DbSet<Grandchild2> Grandchildren2 { get; set; }

      public DbSet<Grandchild3> Grandchildren3 { get; set; }


      public Parent GetParent()
      {
          Parent parent = Parents
              .Include(p => p.Son).ThenInclude(c => c.Grandchildren1)
              .Include(p => p.Son).ThenInclude(c => c.Grandchildren2)
              .Include(p => p.Son).ThenInclude(c => c.Grandchildren3)
              .FirstOrDefault(p =>
              p.Name == "ParentName" &&
              p.Son.Name == "ChildName");
          return parent;
      }
  }