c# - EF6 POCO 无法在 1..* 关系中转换 HashSet 类型的对象

Question

我正在尝试针对具有以下结构的现有数据库使用 Entity Framework 6 和 POCO:

Departments
DepartmentID        UNIQUEIDENTIFIER      NOT NULL PK
SortOrder               INT                                  NULL
Image                     IMAGE                            NULL
Status                     BIT                                  NULL
LastUpdated           DATETIME                      NOT NULL
UpdatedBy             NVARCHAR(10)              NULL
Approved                BIT                                  NOT NULL
ApprovedBy            NVARCHAR(10)             NULL
ApprovedDate         DATETIME                     NULL
ParentDepartment   UNIQUEIDENTIFIER     NULL

DepartmentDescriptions
DepartmentID   UNIQUEIDENTIFIER   NOT NULL PK, FK
LocaleID           INT                                NOT NULL PK, FK
Description       NVARCHAR(50)           NOT NULL

Locales
LocaleID           INT                       NOT NULL PK
ShortString       NVARCHAR(10)   NOT NULL
Description       NVARCHAR(50)   NOT NULL
Status               BIT                        NOT NULL

我的类(class)是:

public class Department
{
    [Key]
    public Guid DepartmentID { get; set; }
    public Int32? SortOrder { get; set; }
    public Byte[] Image { get; set; }
    public Boolean Status { get; set; }
    public DateTime LastUpdated { get; set; }
    public String UpdatedBy { get; set; }
    public Boolean Approved { get; set; }
    public String ApprovedBy { get; set; }
    public DateTime ApprovedDate { get; set; }
    public Guid? ParentDepartment { get; set; }

    // Navigation Properties
    public virtual ICollection<DepartmentDescription> DepartmentDescriptions { get; set; }

    public Department()
    {
        DepartmentDescriptions = new HashSet<DepartmentDescription>();
    }

}


public class DepartmentDescription
{
    [Key]
    public Guid DepartmentID { get; set; }
    public Int32 LocaleID { get; set; }
    public String Description { get; set; }

    // Navigation Properties
    [ForeignKey("DepartmentID"), Required] 
    public virtual Department Department { get; set; }

    [ForeignKey("LocaleID"), Required]
    public virtual Locale Locale { get; set; }

}

public class Locale
{
    [Key]
    public Int32 LocaleID { get; set; }
    public String ShortString { get; set; }
    public String Description { get; set; }
    public Boolean Status { get; set; }

    // Navigation Properties
    public virtual ICollection<DepartmentDescription> DepartmentDescriptions { get; set; }

    public Locale()
    {
        DepartmentDescriptions = new HashSet<DepartmentDescription>();
    }
}

当我尝试向上下文添加新部门时，我得到:

*Unable to cast object of type 'System.Collections.Generic.HashSet`1[DepartmentDescription]' to type 'DepartmentDescription'.*  

添加新部门的代码(释义)是:

Department _department = new Department
    {
        DepartmentID = new Guid("aed99956-c3e1-44a7-b09a-00169f64bdff"),
        Status = true, 
        SortOrder = 320, 
        Image = null, 
        Approved = true, 
        ApprovedBy = "Import", 
        ApprovedDate = Convert.ToDateTime("11/22/2016 3:40:50PM"), 
        LastUpdated = Convert.ToDateTime("11/22/2016 3:40:50PM"), 
        UpdatedBy = Import
    };  

DepartmentDescription _description = new DepartmentDescription 
    {
        DepartmentID = new Guid("aed99956-c3e1-44a7-b09a-00169f64bdff"),
        LocaleID = 1033, 
        Description = "Department Description"
    };

_department.DepartmentDescriptions.Add(_description);
context.Departments.Add(_department);  

我确信我正在做的事情值得被打脸，但我已经盯着它看太久了，看不出我错过了什么。任何建议将不胜感激!

Answer 1

DepartmentDescriptions 表有一个复合主键，它不由 DepartmentDescription 类表示。因此，DbContext 正在尝试使用未正确映射到数据库架构的 POCO 来执行其神奇的 ORM 操作。

使用 DataAnnotations，DepartmentDescription 类应该如下所示:

public class DepartmentDescription
{
   [Key]
   [Column(Order = 1)]
   public Guid DepartmentID { get; set; }
   [Key]
   [Column(Order = 2)]
   public Int32 LocaleID { get; set; }
   public String Description { get; set; }

   // Navigation Properties
   [ForeignKey("DepartmentID"), Required]
   public virtual Department Department { get; set; }

   [ForeignKey("LocaleID"), Required]
   public virtual Locale Locale { get; set; }

}