c# - 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 网络应用程序，以将旧的遗留 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，而是在 SQL View 中全部完成。我希望通过此应用程序解决的问题。

当外键属于同一类类型时，我想确保自己全神贯注地设置外键。例如，我有以下类(class)。

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; }
        ...
    }
}

我在项目类末尾的键看起来像这样吗？

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; }

还有我的 DbContext 类中的模型生成器

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 类的多重关系。我是否需要像 public ICollection<Project> PmProjects { get; set; } 一样单独处理它们？ ？

Answer 1

是的，您需要有单独的项目集合。

在 Employee 中，您将拥有:

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

在 Project 中，您将:

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

构建器将是:

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");
 });