Entity Framework根据实体的EntityState状态实现增删改查

static void EditAdvance()
{
     using (StudentSystemEntities dbContext = new StudentSystemEntities())
      {
           // 将EF执行的SQL语句输出到控制台
           dbContext.Database.Log += p => Console.WriteLine(p);
           // 创建要修改的对象
           Student stu = new Student()
           {
                 StudentID = 14,
                 Age = 690
            };
            // 通过上下文获取对象相关信息
            DbEntityEntry<Student> entry = dbContext.Entry<Student>(stu);
            // 对象的状态是没有修改
            entry.State = System.Data.Entity.EntityState.Unchanged;
            // 对象的属性值Age修改了
            entry.Property("Age").IsModified = true;
            // 保存修改 会智能判断哪个对象的哪个属性值修改了
            dbContext.SaveChanges();
            Console.WriteLine("修改成功");
     }
}

static void DeleteAdvance()
{
     using (StudentSystemEntities dbContext = new StudentSystemEntities())
     {
         // 将EF执行的SQL语句输出到控制台
         dbContext.Database.Log += p => Console.WriteLine(p);
         // 先查询然后在删除
         Student stu = new Student()
         {
               StudentID = 14
          };
          DbEntityEntry<Student> entry = dbContext.Entry<Student>(stu);
          entry.State = System.Data.Entity.EntityState.Deleted;
          // 保存,智能判断对象的状态
          dbContext.SaveChanges();
          Console.WriteLine("删除成功");
      }
}

static void AddAdvance()
{
     using (StudentSystemEntities dbContext = new StudentSystemEntities())
      {
          // 定义Student对象
          Student stu = new Student()
          {
               StudentName = "花千骨",
               Sex = "女",
               Age = 3422,
               Major = "舞蹈专业",
               Email = "2345678911@qq.com"
           };
           // 将EF执行的SQL语句输出到控制台
           dbContext.Database.Log += p => Console.WriteLine(p);
           DbEntityEntry<Student> entry = dbContext.Entry<Student>(stu);
           entry.State = System.Data.Entity.EntityState.Added;
            // 保存的数据库
            dbContext.SaveChanges();
            Console.WriteLine("保存成功");
      }
}

static void Save()
{
      using (StudentSystemEntities dbContext = new StudentSystemEntities())
      {
           // 将EF执行的SQL语句输出到控制台
           dbContext.Database.Log += p => Console.WriteLine(p);
           // 新增数据1
           Student stu1 = new Student()
           {
               StudentName = "红孩儿",
               Age = 456,
               Major = "冶金专业"
            };
            dbContext.Students.Add(stu1);

            // 新增数据2
            Student stu2 = new Student()
            {
                StudentName = "青牛精",
                Age = 345,
                Major = "炼丹"
             };
             // 使用状态
             DbEntityEntry<Student> entry = dbContext.Entry<Student>(stu2);
              entry.State = System.Data.Entity.EntityState.Added;

              // 修改数据
              Student stuEdit = new Student()
              {
                    StudentID=5,
                    Age=678
              };
              //状态
              DbEntityEntry<Student> entryEdit = dbContext.Entry<Student>(stuEdit);
              entryEdit.State = System.Data.Entity.EntityState.Unchanged;
              entryEdit.Property("Age").IsModified = true;

              // 删除数据
              Student stuDel = new Student()
              {
                   StudentID=22
              };
              DbEntityEntry<Student> entryDel = dbContext.Entry<Student>(stuDel);
              entryDel.State = System.Data.Entity.EntityState.Deleted;

              // 保存
              dbContext.SaveChanges();
              Console.WriteLine("保存成功");
      }
}