在 .Net Core / EF Core 中设置多个相同类的外键

Question

我正在构建一个 .Net Core Web 应用程序，以将旧的旧式 Access ADP/ADE 前端替换为项目管理 SQL Server 数据库。然而，原始数据库的构建者并没有设置大量的外键关系，而是为了在 SQL 视图中完成所有操作。我希望用这个应用程序来补救。

当外键属于相同的类类型时，我想确保我的头脑集中在设置外键上。例如，我有以下课程。

项目.cs

using System;
using System.Collections.Generic;

namespace ProjectLogic.Models
{
    public class Project
    {
        public int Id { get; set; };
        public string Name { get; set; }
        public int? PmEmployeeId { get; set; }
        public int? CadEmployeeId { get; set; }
        public int? SalesRepEmployeeId { get; set; }
        ...
    }
}

员工.cs

using System;
using System.Collections.Generic;

namespace ProjectLogic.Models
{
    public class Employee
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public string Title { get; set; }
        ...
    }
}

我在项目课程结束时的钥匙会像这样吗？

public Employee PmEmployee { get; set; }
public Employee CadEmployee { get; set; }
public Employee SalesRepEmployee { get; set; }

在 Employee 类中有相应的声明

public ICollection<Project> Projects { get; set; }

以及我的 DbContext 类中的模型构建器

modelBuilder.Entity<Project>(entity =>
{
// Fluent API for column properties
...
entity.HasOne(d => d.PmEmployee)
    .WithMany(p => p.Projects)
    .HasForeignKey(d => d.PmEmployeeId)
    .OnDelete(DeleteBehavior.SetNull)
    .HasConstraintName("FK_Project_Employee_PM");

entity.HasOne(d => d.CadEmployee)
    .WithMany(p => p.Projects)
    .HasForeignKey(d => d.CadEmployeeId)
    .OnDelete(DeleteBehavior.SetNull)
    .HasConstraintName("FK_Project_Employee_CAD");

entity.HasOne(d => d.SalesRepEmployee)
    .WithMany(p => p.Projects)
    .HasForeignKey(d => d.SalesRepEmployeeId)
    .OnDelete(DeleteBehavior.SetNull)
    .HasConstraintName("FK_Project_Employee_SALES");
});

我想我最大的担忧/问题是 Employee 类将如何处理与 Project 类的多种关系。我是否也需要单独处理这些public ICollection<Project> PmProjects { get; set; }？

Answer 1

是的，您需要有单独的项目集合。

在员工中，您将拥有：

public ICollection<Project> PmProjects { get; set; }
public ICollection<Project> CadProjects { get; set; }
public ICollection<Project> SalesProjects { get; set; }

在项目中，您将拥有：

public Employee PmEmployee { get; set; }
public Employee CadEmployee { get; set; }
public Employee SalesRepEmployee { get; set; }

建造者将是：

modelBuilder.Entity<Project>(entity =>
{
// Fluent API for column properties
...
entity.HasOne(d => d.PmEmployee)
    .WithMany(p => p.PmProjects)
    .HasForeignKey(d => d.PmEmployeeId)
    .OnDelete(DeleteBehavior.SetNull)
    .HasConstraintName("FK_Project_Employee_PM");

entity.HasOne(d => d.CadEmployee)
    .WithMany(p => p.CadProjects)
    .HasForeignKey(d => d.CadEmployeeId)
    .OnDelete(DeleteBehavior.SetNull)
    .HasConstraintName("FK_Project_Employee_CAD");

 entity.HasOne(d => d.SalesRepEmployee)
    .WithMany(p => p.SalesProjects)
    .HasForeignKey(d => d.SalesRepEmployeeId)
    .OnDelete(DeleteBehavior.SetNull)
    .HasConstraintName("FK_Project_Employee_SALES");
 });