1.2 EntityFramework简单增删改查

//添加对象
            Students objStudent = new Students()
            {
                StudentAddress = "天津市南开区",
                StudentName = "CZB",
                Age = 26,
                Birthday = Convert.ToDateTime("1992-02-29"),
                ClassId = 2,
                Gender = "男",
                PhoneNumber = "022-99008877",
                StudentIdNo = 120223199601011213
            };
            EFDBEntities efdb = new EFDBEntities();
            efdb.Students.Add(objStudent);//将实体对象添加到数据库上下文对应的对象集合中
            int result = efdb.SaveChanges();//将数据库上下文的更改保存到数据库中

            Console.WriteLine(result);
            Console.ReadLine();
           

//删除对象
            EFDBEntities efdb = new EFDBEntities();
            //想修改对象，首先找到要修改的对象
            Students objStudent = efdb.Students.FirstOrDefault(s => s.StudentId == 100012);

            efdb.Students.Remove(objStudent);

            int result = efdb.SaveChanges();
            Console.WriteLine(result);
            Console.ReadLine();
           

//查询对象
            //创建数据库上下文对象
            EFDBEntities efdb = new EFDBEntities();
            Students objStudent = efdb.Students.SingleOrDefault(s => s.StudentName ==               "CZB");
            if (objStudent != null)
            {
                Console.WriteLine(objStudent.StudentName + "  " + objStudent.StudentId);
            }

            //使用where()查询符合条件的数据
            IQueryable<Students> query = efdb.Students.Where(s => s.StudentId > 100002);
            Console.WriteLine("学号\t姓名\t年龄");
            foreach (var item in query)
            {
                Console.WriteLine("{0}\t{1}\t{2}", item.StudentId, item.StudentName, item.Age);
            }
            Console.ReadLine();
           

//修改对象
            EFDBEntities efdb = new EFDBEntities();
            //想修改对象，首先找到要修改的对象
            Students objStudent = efdb.Students.FirstOrDefault(s => s.StudentId == 100012);
            //Students objStudent = (from s in efdb.Students
            //                       where s.StudentId == 100012
            //                       select s).First<Students>();
            //在此修改各个属性值
            objStudent.StudentAddress = "哈哈哈";
            objStudent.PhoneNumber = "888888888";
            int result = efdb.SaveChanges();
            Console.WriteLine(result);
            Console.ReadLine();