//状态跟踪类型测试
static void Status()
{
StudentManageDBEntities db = new StudentManageDBEntities();
//创建一个对象：当前对象的状态为detached
Students student = new Students
{
StudentName = "龚均强",
Gender = "男",
Birthday = Convert.ToDateTime("1991-04-22"),
StudentIdNo = 520722199104221978,
CardNo = "2958141",
Age = 28,
PhoneNumber = "18408230331",
StudentAddress = "西华大学",
ClassId = 1,
};
Console.WriteLine(db.Entry(student).State.ToString());
//添加到缓存对象中：状态为Added
db.Students.Add(student);
Console.WriteLine(db.Entry(student).State.ToString());
//保存后：UnChanged
db.SaveChanges();
Console.WriteLine(db.Entry(student).State.ToString());
}
//状态跟踪与无状态跟踪
static void StatusTracking()
{
StudentManageDBEntities db = new StudentManageDBEntities();
//状态跟踪查询：UnChanged
var stu1 = (from o in db.Students select o).FirstOrDefault();
Console.WriteLine(db.Entry(stu1).State.ToString());
//无状态查询：detached 查询不被跟踪，好处：提升性能，返回实体不缓存，适合纯粹查询
var stu2 = db.Students.AsNoTracking().Select(o => o).FirstOrDefault();
Console.WriteLine(db.Entry(stu2).State.ToString());
}
/// <summary>
/// 编辑：修改
/// </summary>
static void Modify()
{
//【1】数据验证
//【2】对象封装
Students student = new Students
{
StudentId = 100012,
StudentName = "龚均强",
Gender = "男",
Birthday = Convert.ToDateTime("1991-04-22"),
StudentIdNo = 510722199104221978,
CardNo = "0000000",
Age = 28,
PhoneNumber = "18408230331",
StudentAddress = "西华大学",
ClassId = 2,
};
//【3】创建数据库上下文对象
StudentManageDBEntities db = new StudentManageDBEntities();
db.Students.Attach(student);
db.Entry(student).State = EntityState.Modified; //设置对象的状态为修改
int result = db.SaveChanges(); //跟新到数据库（自动生成SQL语句）
Console.WriteLine(result);
Console.WriteLine("学号：" + student.StudentId);
}
static void DeleteStudents()
{
//根据主键构建一个对象
Students student = new Students
{
StudentId = 100000
};
//第一种写法：通过设置状态
using (StudentManageDBEntities db = new StudentManageDBEntities())
{
db.Set <Students>().Attach(student);
db.Entry(student).State = EntityState.Deleted;
db.SaveChanges();
}
//第二种写法：通过remove方法
using (StudentManageDBEntities db = new StudentManageDBEntities())
{
db.Set <Students>().Attach(student);
db.Students.Remove(student);
db.SaveChanges();//跟新到数据库（自动生成SQL语句）
}
//第三种写法：先查寻，再删除
using (StudentManageDBEntities db = new StudentManageDBEntities())
{
var stu = db.Students.Where(o => o.StudentId == 100000).FirstOrDefault();
db.Students.Remove(stu);
db.SaveChanges();//跟新到数据库（自动生成SQL语句）
}
}
static void UpdateStudents()
{
Students student = new Students
{
StudentName = "龚均强",
Gender = "男",
Birthday = Convert.ToDateTime("1991-04-22"),
StudentIdNo = 510722199104221978,
CardNo = "1958141",
Age = 28,
PhoneNumber = "18408230331",
StudentAddress = "西华大学",
ClassId = 1,
};
//第一种写法：构建全部属性对象修改
using (StudentManageDBEntities db = new StudentManageDBEntities())
{
//db.Students.Attach(student);//可以省略，将student实体添加到上下文中
db.Entry(student).State = EntityState.Modified;
db.SaveChanges();
}
//第二种写法：先查询再修改
using (StudentManageDBEntities db = new StudentManageDBEntities())
{
//查询对象
var stu = db.Students.FirstOrDefault(o => o.StudentId == 100012);
//修改对象属性
stu.StudentAddress = "红哇小区";
//提交修改
db.SaveChanges();//跟新到数据库（自动生成SQL语句）
}
}
static void AddStudents()
{
Students student = new Students
{
StudentName = "龚均强",
Gender = "男",
Birthday = Convert.ToDateTime("1991-04-22"),
StudentIdNo = 510722199104221978,
CardNo = "1958141",
Age = 28,
PhoneNumber = "18408230331",
StudentAddress = "西华大学",
ClassId = 1,
};
//第一种写法：
using (StudentManageDBEntities db = new StudentManageDBEntities())
{
db.Entry(student).State = EntityState.Added;
db.SaveChanges();
}
//第二种写法：
using (StudentManageDBEntities db = new StudentManageDBEntities())
{
//db.Students.Attach(student);//可以省略，将student实体添加到上下文中
db.Students.Add(student);
db.SaveChanges();
}
}
static void Delete2()
{
StudentManageDBEntities db = new StudentManageDBEntities();
Students student = new Students
{
StudentId = 100013,
};
db.Set <Students>().Attach(student);
db.Entry(student).State = EntityState.Deleted;
//提交
int result = db.SaveChanges();//跟新到数据库（自动生成SQL语句）
Console.WriteLine("影响行数：" + result);
}