EF ORM

             //新增
            UserInfo userInfo = new UserInfo();
            userInfo.UserName = "YANG";
            userInfo.UserPass = "123";
            userInfo.Email = "[email protected]";
            userInfo.RegTime = System.DateTime.Now;

            Model1Container db = new Model1Container();
            db.UserInfoSet.Add(userInfo);
            db.SaveChanges();
            Response.Write(userInfo.Id); 
            //删除
            UserInfo userInfo = new UserInfo() { Id = 2 };
            Model1Container db =new Model1Container();
            // db.UserInfoSet.Remove(userInfo);//必须提前知道对象，不然报错，找不到对象
            db.Entry<UserInfo>(userInfo).State = System.Data.Entity.EntityState.Deleted;
            db.SaveChanges();
            //查询
            Model1Container db = new Model1Container();
            var userInfoList = from u in db.UserInfoSet
                               where u.Id == 2
                               select u;
            foreach (var userInfor in userInfoList)
            {
                Response.Write(userInfor.UserName);
            }
            //修改
            Model1Container db = new Model1Container();
            var userInfoList = from u in db.UserInfoSet
                               where u.Id == 3
                               select u;
            var userInfo = userInfoList.FirstOrDefault();
            userInfo.UserName = "成龙";
            db.Entry<UserInfo>(userInfo).State = System.Data.Entity.EntityState.Modified;
            db.SaveChanges();  
          //一对多 新增 
            Model2Container db = new Model2Container();
            Customer customer = new Customer() { CustomerName = "张三", CustomerPwd = "123", SubTime = DateTime.Now };
            OrderInfo orderInfo1 = new OrderInfo() { id = Guid.NewGuid(), OrderNum = "10001", CreateDateTime = DateTime.Now, Customer = customer };
            OrderInfo orderInfo2 = new OrderInfo() { id = Guid.NewGuid(), OrderNum = "10002", CreateDateTime = DateTime.Now, Customer = customer };
            OrderInfo orderInfo3 = new OrderInfo() { id = Guid.NewGuid(), OrderNum = "10003", CreateDateTime = DateTime.Now, Customer = customer };
            db.CustomerSet.Add(customer);
            db.OrderInfoSet.Add(orderInfo1);
            db.OrderInfoSet.Add(orderInfo2);
            db.OrderInfoSet.Add(orderInfo3);
            db.SaveChanges(); 
         .// 查询部分列
         Model1Container db =new Model1Container();
            var userInfoList = from u in db.UserInfoSet
                               where u.Id == 3
                               select new { userName = u.UserName, userPwd = u.UserPass };
            foreach (var userInfo in userInfoList)
            {
                Response.Write(userInfo.userName + ":" + userInfo.userPwd);
            }
           //lamda表达式
           Model1Container db = new Model1Container();
            var userInfoList = db.UserInfoSet.Where<UserInfo>(u => u.Id > 4).OrderBy<UserInfo, int>(u=>u.Id);
            foreach (var userInfo in userInfoList)
            {
                Response.Write(userInfo.UserName + ":" + userInfo.UserPass);
            }
            // 分页
            //Model1Container db = new Model1Container();
            //为了解决访问过程中出现多个EF连接，利用HttpContext对象的线程唯一对象属性，判断db访问对象是否存在 
            Model1Container db = null;
            if (HttpContext.Current.Items["db"] == null)
            {
                db = new Model1Container();
                HttpContext.Current.Items["db"] = db;
            }
            else
            {
                db = HttpContext.Current.Items["db"] as Model1Container;
            }
            int pageSize = 2;
            int pageIndex = 2;
            var userInfoList = db.UserInfoSet.Where<UserInfo>(u => true).OrderByDescending<UserInfo, int>(u => u.Id).Skip<UserInfo>((pageIndex-1)*pageSize).Take<UserInfo>(pageSize);       //如果转换为List，就无延迟加载 
            foreach (var userInfo in userInfoList)
            {
                Response.Write(userInfo.UserName + ":" + userInfo.UserPass+"<br/>");
            } 
            
            
            var userInfoList = db.UserInfoSet.Where<UserInfo>(u => u.Id > 0);//有延迟加载
            var userInfoList1 = db.UserInfoSet.Where<UserInfo>(u => u.Id > 0).ToList();//无延迟加载，直接将数据加载到内存中