c# - EF6 必需-可选关系（一对零或一）无法正常工作

Question

我有一对零或一的关系，我遇到的问题是依赖实体到主体实体的导航属性始终为空，除非首先从其 DbSet 加载主体实体。

数据库关系是 Employee.ID -> TrainerProfile.TrainerID，其中 TrainerID 是主键和外键。

实体是使用 [Column] 属性映射的 Employee.Id -> TrainerProfile.Id。

//Principal
public class Employee : BaseEntity<int>
{
    [Key]
    [Column("ID")]
    public override int Id { get; protected set; }

    [Required(ErrorMessage = "A Username is required")]
    [DataType(DataType.Text)]
    [StringLength(256)]
    public string UserName { get; set; }

    [Required(ErrorMessage = "A First Name is required")]
    [StringLength(40)]
    public string FName { get; set; }

    [Required(ErrorMessage = "A Last Name is required")]
    [StringLength(40)]
    public string LName { get; set; }
    ...
}

//Dependent
public class TrainerProfile : BaseEntity<int>
{   
    private TrainerProfile()
    {
    } 

    protected TrainerProfile(int id) : base(id)
    {
    }

    [Key]
    [Column("TrainerID")]
    public override int Id { get; protected set; }

    public bool Passport { get; set; }

    [StringLength(1000)]
    public string SpecialConsiderations { get; set; }

    [StringLength(10)]
    public string SeatPreference { get; set; }

    [ForeignKey("Id")]
    public virtual Employee Employee { get; set; }
}


//DBContext OnModelCreating()
modelBuilder.Entity<Employee>()
            .HasOptional(e => e.TrainerProfile)
            .WithRequired(e => e.Employee);

modelBuilder.Entity<TrainerProfile>()
            .HasKey(e => e.Id)
            .HasRequired(e => e.Employee)
            .WithOptional(e => e.TrainerProfile);

更新

var db = new DBContext();
var profile = db.TrainerProfiles.First(); //profile.Employee null
var employee = db.Employees.List(); //profile.Employee now loaded

标签： c#entity-frameworkentity-framework-6

Answer 1

我能够通过将默认构造函数访问器从私有更改为受保护来解决这个问题。

//Dependent
public class TrainerProfile : BaseEntity<int>
{   
    protected TrainerProfile() //***Changed from private to protected***
    {
    } 

    protected TrainerProfile(int id) : base(id)
    {
    }

    [Key]
    [Column("TrainerID")]
    public override int Id { get; protected set; }

    public bool Passport { get; set; }

    [StringLength(1000)]
    public string SpecialConsiderations { get; set; }

    [StringLength(10)]
    public string SeatPreference { get; set; }

    [ForeignKey("Id")]
    public virtual Employee Employee { get; set; }
}