增+查

using EFDemo01.Modules;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data.Entity.Validation;

namespace EFDemo01
{
    internal class Program
    {
        static void Main(string[] args)
        {
            using (var db = new DBModel())
            {
                /**
                 */
                //person表insert数据
                db.people.Add(new person { name = "张三", age = 20, position = "码农", departmentId = 2 });
                db.people.Add(new person { name = "李四", age = 19, position = "工程", departmentId = 3 });
                //department表insert数据
                db.departments.Add(new department { departmentName = "SI" });
                db.departments.Add(new department { departmentName = "CIM" });
                db.departments.Add(new department { departmentName = "TED" });
                //提交transact sql
                db.SaveChanges();

                //查
                var resultPeople = db.people.Where(p => p.age >= 20).DefaultIfEmpty();
                foreach (var per in resultPeople)
                {
                    Console.WriteLine($"姓名：{per.name}, 年龄：{per.age}, 部门：{per.position}");
                }
                var resultDepartment = from depar in db.departments select depar;
                foreach (var depar in resultDepartment)
                {
                    Console.WriteLine($"部门：{depar.departmentName}");
                }
            }
            Console.Read();
        }
    }
}

改

using EFDemo01.Modules;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data.Entity.Validation;

namespace EFDemo01
{
    internal class Program
    {
        static void Main(string[] args)
        {
            using (var db = new DBModel())
            {
                var resultBeforeUpdate = db.people.Where(p => p.age >= 20).DefaultIfEmpty();

                //改
                var person = db.people.Where(p => p.name=="小明").FirstOrDefault();
                if (person != null)
                {
                    person.age = 22;
                    db.SaveChanges();
                }

                var resultAfterUpdate = db.people.Where(p => p.age >= 20).DefaultIfEmpty();

                Console.WriteLine("修改前：");
                foreach (var per in resultBeforeUpdate)
                {
                    Console.WriteLine($"姓名：{per.name}, 年龄：{per.age}, 部门：{per.position}");
                }
                Console.WriteLine("修改后：");
                foreach (var per in resultAfterUpdate)
                {
                    Console.WriteLine($"姓名：{per.name}, 年龄：{per.age}, 部门：{per.position}");
                }

            }
            Console.Read();
        }
    }
}