orm框架中entityframework的 增删改查操作

/////////////////////第一种//////////////////////////

namespace ConsoleApplication3

{

    class Program

    {

        static void Main(string[] args)

        {

            Model1Container m = new Model1Container();

            Student s = new Student();

            s.Name = "小明";

            m.Student集.AddObject(s);   //增加操作

            m.SaveChanges();            //运行增加

            Console.WriteLine("增加成功");

 

            var Slist = from Stu in m.Student集 select Stu;   //查询操作

            foreach (Student sl in Slist)

            {

                Console.WriteLine("输出的学生名字为:");

                Console.WriteLine(sl.Name);

            }

 

            Console.WriteLine("更新操作");

            Student sc = new Student();

            sc.ID = 2;

            sc.Name = "小改明";

            m.Student集.Attach(sc);   //这句很重要把要更新的实体写入实体集中

            m.ObjectStateManager.ChangeObjectState(sc, System.Data.EntityState.Modified);   //对实体进行更新

            m.SaveChanges();   //运行更新操作

 

            Console.WriteLine("删除操作");

            Student sd = new Student();

            sd.ID = 3;

            m.Student集.Attach(sd);

            m.ObjectStateManager.ChangeObjectState(sd, System.Data.EntityState.Deleted);  //删除操作

            m.SaveChanges();

        }

    }

}

////////////////////////////////////第二种//////////////////////////

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

 

namespace ConsoleApplication1

{

    class Program

    {

        static void Main(string[] args)

        {

            //创建数据库实体

            ModelStudentContainer DemoDB = new ModelStudentContainer();

 

            #region 增加数据

 

            ////创建具体实体（表中一行）

            //Student stu1 = new Student()

            //{

            //    ID = 1,

            //    Name = "张飞",

            //    Age = 20

            //};

            //Student stu2 = new Student()

            //{

            //    ID = 2,

            //    Name = "关羽",

            //    Age = 21

            //};

            //Student stu3 = new Student()

            //{

            //    ID = 3,

            //    Name = "赵云",

            //    Age = 22

            //};

            //Student stu4 = new Student()

            //{

            //    ID = 4,

            //    Name = "刘备",

            //    Age = 23

            //};

            //Student stu5 = new Student()

            //{

            //    ID = 5,

            //    Name = "刘表",

            //    Age = 24

            //};

            //Student stu6 = new Student()

            //{

            //    ID = 6,

            //    Name = "刘禅",

            //    Age = 25

            //};

 

            ////将实体stu添加到数据库实体对象中

            //DemoDB.Student.AddObject(stu1);

            //DemoDB.Student.AddObject(stu2);

            //DemoDB.Student.AddObject(stu3);

            //DemoDB.Student.AddObject(stu4);

            //DemoDB.Student.AddObject(stu5);

            //DemoDB.Student.AddObject(stu6);

 

            ////保存对数据库的修改

            //DemoDB.SaveChanges();

 

            #endregion

 

            #region 查询1：一般查询，查询所有数据

 

            //var result = from u in DemoDB.Student

            //             select u;

 

            //foreach (var item in result)

            //{

            //    Console.WriteLine("ID：{0}，姓名：{1}，年龄：{2}。", item.ID, item.Name, item.Age);

            //}

 

            #endregion

 

            #region 查询2：使用ToList防止延迟加载，拆分子查询

 

            ////这个查询结果可以保存到服务器内存中

            //var result1 = (from u in DemoDB.Student

            //               where u.Age >= 22

            //               select u).ToList();

 

            //var result2 = from u in result1

            //              where u.Name != "赵云"

            //              select u;

 

            //foreach (var item in result2)

            //{

            //    Console.WriteLine("ID：{0}，姓名：{1}，年龄：{2}。", item.ID, item.Name, item.Age);

            //}

 

            #endregion

 

            #region 查询3：使用Where方法（lambda表达式）

 

            ////使用了Where泛型方法，要传入一个lambda表达式

            //var result = DemoDB.Student

            //    .Where(t => t.ID == 1);

 

            //foreach (var item in result)

            //{

            //    Console.WriteLine("ID：{0}，姓名：{1}，年龄：{2}。", item.ID, item.Name, item.Age);

            //}

 

            #endregion

 

            #region 查询4：Linq分页查询

 

            ////要跳过多少页

            //int skipPage;

            ////每页两条数据

            //int countPerPage=2;

 

            ////从跳过0页到跳过2页（输出第1-3页）

            //for (skipPage = 0; skipPage <= 2; skipPage++)

            //{

            //    var result = DemoDB.Student

            ////分页必须排序

            //        .OrderBy(t => t.ID)

            ////跳过指定页数

            //        .Skip(skipPage * countPerPage)

            ////获取条数

            //        .Take(countPerPage);

 

            //    Console.WriteLine("第{0}页：", skipPage + 1);

            ////输出查询结果（该页）

            //    foreach (var item in result)

            //    {

            //        Console.WriteLine("ID：{0}，姓名：{1}，年龄：{2}。", item.ID, item.Name, item.Age);

            //    }

 

            //    Console.WriteLine();

            //}

 

            #endregion

 

            #region 查询5：使用匿名类查询多个字段

 

            //var result = from p in DemoDB.Student

            //             where p.ID < 4

            ////定义一个包含了ID和Name信息的匿名类

            //             select new { p.ID, p.Name };

 

            //foreach (var item in result)

            //{

            ////这里无法输出年龄

            //    Console.WriteLine("ID：{0}，姓名：{1}。", item.ID, item.Name);

            //}

 

            #endregion

 

            #region 修改1：修改1条记录

 

            ////这里没有写where字句，会查询出4条记录

            //var result = from u in DemoDB.Student

            //             select u;

 

            ////但是这个方法一次只能取出一条记录

            ////注：First方法如果返回空值则抛异常

            //var target = result.FirstOrDefault();

            ////所以只修改了查询结果集中的第一条记录

            //target.Name = "司马懿";

 

            //DemoDB.SaveChanges();

 

            #endregion

 

            #region 修改2：修改多条记录

 

            //var result = from u in DemoDB.Student

            //             select u;

 

            ////使用循环方式，修改所有查询到的记录

            //foreach (var item in result)

            //{

            //    item.Age = 10;

            //}

 

            //DemoDB.SaveChanges();

 

            #endregion

 

            #region 删除

 

            //var result = from u in DemoDB.Student

            //             where u.Name == "关羽"

            //             select u;

 

            ////删除所有查询结果（这里只有一条结果）

            //foreach (var item in result)

            //{

            //    DemoDB.Student.DeleteObject(item);

            //}

 

            //DemoDB.SaveChanges();

 

            #endregion

 

            Console.WriteLine("执行完毕！");

            Console.ReadKey();

        }

    }

}

 

转载于:https://www.cnblogs.com/mengqimoli/p/8552520.html