新建 .net core项目
NuGet程序包中添加以下包：

Microsoft.EntityFrameworkCore
Microsoft.EntityFrameworkCore.Tools
Pomelo.EntityFrameworkCore.MySql
Newtonsoft.Json

设计三个类：User、Department、Product 其中User与Department是一对一关系，User与Product是一对多关系。

using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace EFCoreLearn.Models
{
    [Table("t_user")]
    public class User
    {
        [Key]
        public string id { get; set; }

        public string name { get; set; }

        public string password {  get; set; }

        public Department department {  get; set; }

        public List<Product> products { get; set; }

    }
}

using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace EFCoreLearn.Models
{
    [Table("t_department")]
    public class Department
    {
        [Key]
        public string id { get; set; }

        public string departmentName {  get; set; }

        public string userId {  get; set; }
    }
}

using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace EFCoreLearn.Models
{

    [Table("t_product")]
    public class Product
    {
        [Key]
        public string id { get; set; }


        public string productName {  get; set; }

        public string userId {  get; set; }

    }
}

创建CustomMigrationsSqlGenerator类，编写代码取消数据库迁移时生成的外键。

using Microsoft.EntityFrameworkCore.Metadata;
using Microsoft.EntityFrameworkCore.Migrations;

namespace EFCoreLearn.Models
{
    public class CustomMigrationsSqlGenerator : MigrationsSqlGenerator
    {
        public CustomMigrationsSqlGenerator(MigrationsSqlGeneratorDependencies dependencies, IMigrationsAnnotationProvider migrationsAnnotations) : base(dependencies)
        {
        }

        protected override void Generate(Microsoft.EntityFrameworkCore.Migrations.Operations.CreateTableOperation operation, IModel? model, MigrationCommandListBuilder builder, bool terminate = true)
        {
            operation.ForeignKeys.Clear();
            base.Generate(operation, model, builder, terminate);
        }
    }
}

创建UserContext类继承DbContext，重写OnConfiguring方法，在方法中应用刚才写的CustomMigrationsSqlGenerator

using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Migrations;

namespace EFCoreLearn.Models
{
    public partial class UserContext : DbContext
    {
        public UserContext()
        {
        }

        public UserContext(DbContextOptions<UserContext> options) : base(options)
        {
        }

        //这行代码定义了一个 User 属性，该属性表示数据库中的用户表。
        //通过在 DbContext 中声明这样的属性，Entity Framework Core 就能够跟踪和操作与该实体类相关联的数据库表。
        //当你对 User 属性进行查询、插入、更新或删除时，
        //Entity Framework Core 会负责将这些操作转化为相应的 SQL 查询并与数据库进行交互。
        public DbSet<User> User { get; set; } = null!;

        public DbSet<Department> department {  get; set; } = null!;

        public DbSet<Product> product { get; set; } = null!;


        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.ReplaceService<IMigrationsSqlGenerator, CustomMigrationsSqlGenerator>();
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.UseCollation("utf8_general_ci").HasCharSet("utf8");

            modelBuilder.Entity<User>().HasMany(e => e.products); //user 与 product一对多
            modelBuilder.Entity<User>().HasOne(e => e.department); //user 与 department 一对一

            OnModelCreatingPartial(modelBuilder);
        }

        partial void OnModelCreatingPartial(ModelBuilder modelBuilder);
    }

}

执行数据库迁移（根据代码配置自动生成数据库表）
在vs的程序包管理控制台中输入

add-migration init
update-database

检查数据库中生成的表

写接口测试

using EFCoreLearn.Models;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using Newtonsoft.Json;


namespace EFCoreLearn.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class TestController : ControllerBase
    {
        UserContext userContext;

       
        public TestController(UserContext userContext)
        {
            this.userContext = userContext;
        }

        /// <summary>
        /// 添加用户 部门 产品
        /// </summary>
        /// <param name="user"></param>
        /// <returns></returns>
        [HttpPost("add")]
        public ObjectResult add()
        {   
            User user = new User();
            user.id = Guid.NewGuid().ToString();
            user.name = "zhangsan";
            user.password = "123456";
            user.department = new Department {
                id = Guid.NewGuid().ToString(),
                departmentName = "IT部",
                userId = user.id
            };
            user.products = new List<Product> { 
                new Product {id=Guid.NewGuid().ToString(),productName="键盘",userId=user.id},
                new Product {id=Guid.NewGuid().ToString(),productName="鼠标",userId=user.id}
            };
            
            userContext.User.Add(user);
            userContext.SaveChanges();
            return new ObjectResult("ok");
        }

        /// <summary>
        /// 添加用户
        /// </summary>
        /// <returns></returns>
        [HttpPost("addUser")]
        public ObjectResult addUser() {
            User user = new User();
            user.id = Guid.NewGuid().ToString();
            user.name = "lisi";
            user.password = "123456";

            userContext.User.Add(user);
            userContext.SaveChanges();

            return new ObjectResult("ok");
        }


        /// <summary>
        /// 获取列表（用户 部门 产品）
        /// </summary>
        /// <returns></returns>
        [HttpGet("list")]
        public ActionResult list()
        {
            //var list = userContext.User.Include(a => a.products).Include(a=>a.department).Single<User>(e=>e.id=="03038eca-4b53-4b31-87dc-de5b568923a4");
            var list = userContext.User.Include(a => a.products).Include(a => a.department).ToList();
            if (list == null)
            {
                return new JsonResult("list is null");
            }
            var result = JsonConvert.SerializeObject(list);
            return Content(result, "application/json");
        }

        /// <summary>
        /// 更新 用户 部门 产品
        /// </summary>
        /// <returns></returns>
        [HttpPut("update")]
        public ObjectResult update() {

            User user = new User();
            user.id = "03038eca-4b53-4b31-87dc-de5b568923a4"; //要修改的用户的id
            user.name = "zhangsan_update";
            user.password = "123456_update";
            user.department = new Department
            {
                id = "a099a496-cde0-4495-9701-afd79228be8d",
                departmentName = "IT部_update",
                userId = user.id
            };
            user.products = new List<Product> {
                new Product {id="2afbf390-49d2-4737-bba4-c8fbcb160914",productName="键盘_update",userId=user.id},
                new Product {id="92bcbc28-b671-47a1-9a3c-24faba8338a9",productName="鼠标_update",userId=user.id}
            };

            userContext.User.Update(user);
            userContext.SaveChanges();
            return new ObjectResult("ok");
        }


        /// <summary>
        /// 更新 用户 
        /// </summary>
        /// <returns></returns>
        [HttpPut("updateUser")]
        public ObjectResult updateUser()
        {

            User user = new User();
            user.id = "5705f49f-0d24-4723-a524-f14808a59274"; //要修改的用户的id
            user.name = "lisi_update";
            user.password = "123456_update";
            

            userContext.User.Update(user);
            userContext.SaveChanges();
            return new ObjectResult("ok");
        }

    }
}