使用代码首先在实体框架问题建模关系 [英] Problem modelling relationship in Entity Framework using code first

问题描述

我想先在实体框架内学习码时遇到了问题建模的关系。这是一个基本的人力资源数据库，这对于这个份上有两个实体，员工和部门。

I'm trying to learn code first within the Entity Framework and am having trouble modelling a relationship. It's a basic HR database which for the sake of this has two entities, Employees and Departments.

该员工属于一个部门，该部门拥有一支由管理员和经理，他们两人都在影响员工。我已经试过这使用以下模型：

The Employee belongs to a department and the department has a Team Administrator and a Manager, both of whom are in effect employees. I've tried to model this using the following:

EMPLOYEE

public int? DepartmentID { get; set; }
public virtual Department Department { get; set; }

Context:

modelBuilder.Entity<Employee>().HasOptional(x => x.Department);

DEPARTMENT

public class Department
{
    [Required]
    public int DepartmentID { get; set; }

    [Required(ErrorMessage = "The description is required.")]
    public string Description { get; set; }

    public int? ManagerID { get; set; }
    public virtual Employee Manager { get; set; }

    public int? TeamAdministratorID { get; set; }
    public virtual Employee TeamAdministrator { get; set; }
}

Context:

modelBuilder.Entity<Department>().HasOptional(x => x.Manager);
modelBuilder.Entity<Department>().HasOptional(x => x.TeamAdministrator);

显然，我希望Department表只具有四列 - 的DepartmentID，说明，经理ID和TeamAdministratorID但它产生一个额外的两个用于关系，即Manager_EmployeeID和Team_Administrator_EmployeeID。此外，在雇员表中的列Department_DepartmentID生成到存储中的DepartmentID，而不是它使用我在实体规定的DepartmentID列。

Obviously I would want the Department table to have only four columns - DepartmentID, Description, ManagerID and TeamAdministratorID but it is generating an extra two for the relationship, namely Manager_EmployeeID and Team_Administrator_EmployeeID. Also, in the Employee table the column Department_DepartmentID is generated to store the DepartmentID instead of it using the DepartmentID column I specified in the entity.

我在做什么错了？我如何需要定义字段和关系，以避免代码先不理会我指定并生成它的数据库中的自己的导航领域？

What am I doing wrong? How do I need to define the fields and relationships to avoid having code first ignore what I specify and generate it's own navigation fields in the database?

推荐答案

这是因为你的车型配置是不完整的 - 你流利的API开始自己的映射，所以你必须告诉EF这些属性的确是关系FKS。对于员工使用：

That because your model configuration is incomplete - you started your own mapping with Fluent API so you must tell EF that these properties are indeed FKs for relations. For employee use:

modelBuilder.Entity<Employee>()
            .HasOptional(x => x.Department)
            .WithMany()
            .HasForeignKey(x => x.DepartmentID);

和供部门使用：

modelBuilder.Entity<Department>()
            .HasOptional(x => x.Manager)
            .WithMany()
            .HasForeignKey(x => x.ManagerID);
modelBuilder.Entity<Department>()
            .HasOptional(x => x.TeamAdministrator);
            .WithMany()
            .HasForeignKey(x => x.TeamAdministratorID);

顺便说一句。而对关系的对面集合导航属性将难以用模型（均 WithMany 是空的）。至少处应该有：

Btw. without collection navigation properties on opposite side of relations it will be hard to use model (all WithMany are empty). At least Department should have:

public virtual ICollection<Employee> Employees { get; set;}

和映射应该被修改为：

modelBuilder.Entity<Employee>()
            .HasOptional(x => x.Department)
            .WithMany(y => y.Employees)
            .HasForeignKey(x => x.DepartmentID);

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