/*  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。*/
private void Form1_Load(object sender, EventArgs e)
{
    // 实现EF第一种方式：CodeFirst：代码先行机制
    /************************ 增加数据***********************/
    //01.创建EF上下文实例
    EFFirstEntities efFirst = new EFFirstEntities();
    #region 新增数据
    ////02.构造出一个实体
    //Student stu = new Student();
    //stu.Name = "张三";
    ////03.将实体对象添加到实体集合中
    //efFirst.Student.AddObject(stu);
    ////04.最后要告诉EM帮我去将数据保存到数据库
    //efFirst.SaveChanges();
    #endregion
   /*************************修改数据************************/
   //02.构造出你要修改的实体
    #region 修改数据
    //Student stu = new Student();
    //stu.Name = "李四";
    //stu.ID = 4;
    ////03.将当前实体用EF进行跟踪
    //efFirst.Student.Attach(stu);
    ////04.将状态设置为Modified
    //efFirst.ObjectStateManager.ChangeObjectState(stu, EntityState.Modified);
    ////05.保存
    //efFirst.SaveChanges();
    #endregion  
    /***********************删除数据*************************/
    #region 删除
    //Student stu = new Student();
    //stu.ID = 4;
    ////03.也是要跟踪当前的实体对象
    //efFirst.Student.Attach(stu);
    //efFirst.ObjectStateManager.ChangeObjectState(stu, EntityState.Deleted);
    //efFirst.SaveChanges();
    #endregion
    /***************************查询数据*************/
    //var 语法塘技术
    //foreach (var item in efFirst.Student)
    //{
    //    string result = string.Format("ID={0},Name={1}", item.ID, item.Name);
    //    MessageBox.Show(result);
    //}
    /****************** ***********通过linq方式查询***********/
   //EF有延迟加载机制  select * from student where 1=1
    //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
    var list = from c in efFirst.Student
               where c.ID > 1
               select c;
    foreach (var item in list)
    {
        MessageBox.Show(item.Name);
    } 

ModelFirstStudentContainer modelFirst = new ModelFirstStudentContainer();
/*******************************添加************************************************/
Customer customer = new Customer() { CName = "李小龙", CRemark = "功夫影星" };
modelFirst.Customer.AddObject(customer);
Order order1 = new Order() { OrderContent = "双节棍", Customer = customer, OrderDate = DateTime.Now };
modelFirst.Order.AddObject(order1);
Order order2 = new Order() { OrderContent = "布棍", Customer = customer, OrderDate = DateTime.Now };
modelFirst.Order.AddObject(order2);
modelFirst.SaveChanges();
/*************************************查询*************************************/
var temp = from c in modelFirst.Customer
           where c.Order.Count >= 2
           select c;
foreach (var item in temp)
{
    foreach (var o in item.Order)
    {
        MessageBox.Show(o.OrderContent);
    }
}
/*********************************修改********************************************/
Customer cust = new Customer(){CID = 1,CName = "小李",CRemark = "英雄"};
modelFirst.Customer.Attach(cust);
modelFirst.ObjectStateManager.ChangeObjectState(cust, EntityState.Modified);
modelFirst.SaveChanges();
/*********************************删除***********************************************/
var temp = from c in modelFirst.Order
           where c.Customer.CID == 1 
           select c;
foreach (var item in temp)
{
    modelFirst.Order.DeleteObject(item);
}
Customer cust = new Customer() 
{
    CID=1
};
modelFirst.Customer.Attach(cust);
modelFirst.ObjectStateManager.ChangeObjectState(cust, EntityState.Deleted);
modelFirst.SaveChanges();