灵动思绪EF(Entity FrameWork)

  1  /*  注意点：数据库中的表必须有主键，如果是模型先行，则模型也c必须有主键。
  2 
  3          */
  4 
  5         private void Form1_Load(object sender, EventArgs e)
  6 
  7         {
  8 
  9             // 实现EF第一种方式：CodeFirst：代码先行机制
 10 
 11             /************************ 增加数据***********************/
 12 
 13             //01.创建EF上下文实例
 14 
 15             EFFirstEntities efFirst = new EFFirstEntities();
 16 
 17             #region 新增数据
 18 
 19             ////02.构造出一个实体
 20 
 21             //Student stu = new Student();
 22 
 23             //stu.Name = "张三";
 24 
 25             ////03.将实体对象添加到实体集合中
 26 
 27             //efFirst.Student.AddObject(stu);
 28 
 29             ////04.最后要告诉EM帮我去将数据保存到数据库
 30 
 31             //efFirst.SaveChanges();
 32 
 33             #endregion
 34 
 35            /*************************修改数据************************/
 36 
 37            //02.构造出你要修改的实体
 38 
 39             #region 修改数据
 40 
 41             //Student stu = new Student();
 42 
 43             //stu.Name = "李四";
 44 
 45             //stu.ID = 4;
 46 
 47             ////03.将当前实体用EF进行跟踪
 48 
 49             //efFirst.Student.Attach(stu);
 50 
 51             ////04.将状态设置为Modified
 52 
 53             //efFirst.ObjectStateManager.ChangeObjectState(stu, EntityState.Modified);
 54 
 55             ////05.保存
 56 
 57             //efFirst.SaveChanges();
 58 
 59             #endregion
 60 
 61            
 62 
 63             /***********************删除数据*************************/
 64 
 65             #region 删除
 66 
 67             //Student stu = new Student();
 68 
 69             //stu.ID = 4;
 70 
 71             ////03.也是要跟踪当前的实体对象
 72 
 73             //efFirst.Student.Attach(stu);
 74 
 75             //efFirst.ObjectStateManager.ChangeObjectState(stu, EntityState.Deleted);
 76 
 77             //efFirst.SaveChanges();
 78 
 79             #endregion
 80 
 81  
 82 
 83             /***************************查询数据*************/
 84 
 85             //var 语法塘技术
 86 
 87             //foreach (var item in efFirst.Student)
 88 
 89             //{
 90 
 91             //    string result = string.Format("ID={0},Name={1}", item.ID, item.Name);
 92 
 93             //    MessageBox.Show(result);
 94 
 95             //}
 96 
 97             /****************** ***********通过linq方式查询***********/
 98 
 99            //EF有延迟加载机制  select * from student where 1=1
100 
101             //所谓延迟加载机制，当你真正需要数据的时候，EF才帮我们加载
102 
103             var list = from c in efFirst.Student
104 
105                        where c.ID > 1
106 
107                        select c;
108 
109  
110 
111             foreach (var item in list)
112 
113             {
114 
115                 MessageBox.Show(item.Name);
116 
117             }

 1  ModelFirstStudentContainer modelFirst = new ModelFirstStudentContainer();
 2             /*******************************添加************************************************/
 3             Customer customer = new Customer() { CName = "李小龙", CRemark = "功夫影星" };
 4             modelFirst.Customer.AddObject(customer);
 5             Order order1 = new Order() { OrderContent = "双节棍", Customer = customer, OrderDate = DateTime.Now };
 6             modelFirst.Order.AddObject(order1);
 7 
 8             Order order2 = new Order() { OrderContent = "布棍", Customer = customer, OrderDate = DateTime.Now };
 9             modelFirst.Order.AddObject(order2);
10             modelFirst.SaveChanges();
11             /*************************************查询*************************************/
12             var temp = from c in modelFirst.Customer
13                        where c.Order.Count >= 2
14                        select c;
15             foreach (var item in temp)
16             {
17                 foreach (var o in item.Order)
18                 {
19                     MessageBox.Show(o.OrderContent);
20                 }
21             }
22             /*********************************修改********************************************/
23             Customer cust = new Customer(){CID = 1,CName = "小李",CRemark = "英雄"};
24             modelFirst.Customer.Attach(cust);
25             modelFirst.ObjectStateManager.ChangeObjectState(cust, EntityState.Modified);
26             modelFirst.SaveChanges();
27             /*********************************删除***********************************************/
28             var temp = from c in modelFirst.Order
29                        where c.Customer.CID == 1 
30                        select c;
31             foreach (var item in temp)
32             {
33                 modelFirst.Order.DeleteObject(item);
34             }
35             Customer cust = new Customer() 
36             {
37                 CID=1
38             };
39             
40             modelFirst.Customer.Attach(cust);
41             modelFirst.ObjectStateManager.ChangeObjectState(cust, EntityState.Deleted);
42             modelFirst.SaveChanges();