如何使用 Fluent API 在 Employee 实体和 ICollection<Employee> 之间建立关系？

Question

我正在使用实体框架，并且我在其他实体中有一个 Employee 实体。我希望员工拥有的一个导航属性是该员工管理的员工列表。这是 Employee 类（它实际上使用了 EF 前缀，但我指的是不带前缀的类，以减少混淆）：

/// <summary>
/// The Class model for the Employee Entity
/// </summary>
[Table("employee_entity")]
public class EFEmployee : EFBusinessEntity
{
    /// <summary>
    /// The hire date of the employee
    /// </summary>
    [Column("hire_date")]
    public DateTime HireDate { get; set; }

    /// <summary>
    /// The list of jobtitles for the employee
    /// </summary>
    [Column("job_title")]
    [Required]
    public byte[] JobTitle { get; set; }

    /// <summary>
    /// The Employee's salary (note: not attached to jobtitle necessarily)
    /// </summary>
    [Column("salary")]
    public int Salary { get; set; }

    /// <summary>
    /// List of Certifications for the employee
    /// </summary>
    [Column("certifications")]
    public byte[] Certifications { get; set; }

    /// <summary>
    /// Employee's stored up vacation time
    /// </summary>
    [Column("vacation_time")]
    public int VacationTime { get; set; }

    /// <summary>
    /// Employee's stored up sick time
    /// </summary>
    [Column("sick_time")]
    public int SickTime { get; set; }

    /// <summary>
    /// Maps the employee entity to the office entity
    /// </summary>
    [ForeignKey("office_entity")]
    public virtual EFOffice Office { get; set; }

    /// <summary>
    /// Maps the employee entity to the person entity
    /// </summary>
    public virtual EFPerson Identity { get; set; }

    /// <summary>
    /// Maps the employee entity to another employee entity
    /// </summary>
    public virtual EFEmployee ReportingTo { get; set; }

    /// <summary>
    /// Maps the employee entity to a collection of employee entites
    /// </summary>
    public virtual ICollection<EFEmployee> Managing { get; set; }

    /// <summary>
    /// Constructor for an Entity. Only requires the properties that cannot be null.
    /// </summary>
    /// <param name="Id"></param>
    /// <param name="TenantId"></param>
    /// <param name="hire"></param>
    /// <param name="titles"></param>
    /// <param name="salary"></param>
    /// <param name="certifications"></param>
    /// <param name="vacationTime"></param>
    /// <param name="sickTime"></param>
    public EFEmployee(Guid Id, Guid TenantId, DateTime hire, byte[] titles, int salary, byte[] certifications, int vacationTime, int sickTime)
    {
        this.HireDate = hire;
        this.JobTitle = titles;
        this.Salary = salary;
        this.Certifications = certifications;
        this.SickTime = sickTime;
        this.VacationTime = vacationTime;
    }
}

如您所见，Employee 的导航属性之一是

public virtual ICollection<EFEmployee> Managing { get; set; }

我有一个 EmployeeMap 类，它使用 Fluent API 来建立 Employee 实体和其他实体之间的关系。它现在不完整，但它看起来是这样的：

public partial class EmployeeMap : EntityTypeConfiguration<EFEmployee>
{
    public EmployeeMap()
    {
        // Relations
        HasRequired(t => t.Office).WithMany(u => u.Employees);
        HasMany(t => t.Managing).WithRequired(u => u.Employees);
    }
}

与办公室和员工的第一个关系有效且有意义，因为每个办公室实体都有许多员工实体。但是，第二个关系映射出现错误。具体来说，最后的“员工”给出了一个错误，说

Employee 不包含“Employees”的定义，也没有扩展方法等...

我得到这个错误的原因很明显。我还没有在 Employee for Employees 中声明财产，我不知道为什么要这样做。但是，我如何在相同类型的两个实体之间建立关系呢？如果你回头看看我的 Employee 实体类，我也有导航属性：

public virtual EFEmployee ReportingTo { get; set; }

在这里，我还尝试在 Employee 和另一个 Employee 之间建立关系，但我不知道这将如何工作，因为在实体数据模型中，Employee 实体仅表示为一个具有其属性的表。有谁知道我在说什么以及如何绕过它？

Answer 1

当您定义关系时，您使用的属性需要彼此相反。对于Managing，我认为您正在寻找的是：

HasMany(t => t.Managing).WithRequired(t => t.ReportingTo);

因为我猜你想要：

someEmployee.ReportingTo.Managing.Contains(someEmployee) == true

并且您希望someManager.Managing 中的每个EFEmployee 都拥有ReportingTo == someManager。

---

如果您实际上没有定义逆属性，则不需要在模型配置中定义：

// someEmployee can possibly have many other EFEmployees with 
// ReportingTo == someEmployee, but no collection property on someEmployee to 
// represent that relationship!
HasRequired(t => t.ReportingTo).WithMany();