在.Net Core / EF Core中设置多个相同类的外键答案

【问题标题】：Setting up multiple Foreign keys of same class in .Net Core / EF Core在.Net Core / EF Core中设置多个相同类的外键
【发布时间】：2023-03-31 03:12:01
【问题描述】：

我正在构建一个 .Net Core Web 应用程序，以将旧的 Access ADP/ADE 前端替换为项目管理 SQL Server 数据库。但是，原始数据库的构建者并没有设置很多外键关系，而是在 SQL 视图中完成所有这些。我希望用这个应用程序来补救。

我想确保当外键属于同一类类型时，我已经开始考虑设置外键了。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; }
        ...
    }
}

Employee.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; }
        ...
    }
}

我在项目类结束时的键会像这样吗？

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; }

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 类的多个关系。我需要像public ICollection<Project> PmProjects { get; set; }一样单独处理吗？

【问题讨论】：

标签： c# entity-framework asp.net-core

【解决方案1】：

是的，您需要有单独的项目集合。

在员工中，您将：

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

在 Project 中，您将拥有：

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

建造者是：

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");
 });

【讨论】：