01-Entity FrameWork如何控制数据的变化

 public enum EntityState
    {
        Added = 4,
        Deleted = 8,
        Detached = 1,
        Modified = 0x10,
        Unchanged = 2
    }

    StudentAddress address = new StudentAddress
            {
                Address = "地址" + DateTime.Now
            };
            db.StudentAddress.Add(address);
            Console.WriteLine(db.Entry<StudentAddress>(address).State);//added
            db.SaveChanges();

  StudentAddress address = new StudentAddress
            {
                Address = "地址" + DateTime.Now
            };

            db.Entry<StudentAddress>(address).State = System.Data.Entity.EntityState.Added;
            db.SaveChanges();

            var address2 = db.StudentAddress.FirstOrDefault();
            address2.Address = "ModifyFromEf2";//Modified 
            db.SaveChanges();

   StudentAddress address = new StudentAddress
            {
                Id = 36,
                Address = "update地址"
            };

            //1、追加到EF容器中，状态为Detached
            var entityEntry = db.Entry(address);//Detached 
            entityEntry.State = System.Data.Entity.EntityState.Modified;
            db.SaveChanges();

   //1、追加到EF容器中，状态为Detached
            var entityEntry = db.Entry(address);//Detached
            Console.WriteLine("追加到EF容器：" + entityEntry.State);

            //2、修改指定字段Unchanged-->指定字段为修改
            db.StudentAddress.Attach(address);//相当于entry.State = System.Data.EntityState.Unchanged;   
            Console.WriteLine("Attach-Unchanged:" + entityEntry.State); //Unchanged  

            entityEntry.Property("Address").IsModified = true;
            Console.WriteLine("修改后状态：" + entityEntry.State); //Modified 

            db.SaveChanges();

      StudentAddress address = new StudentAddress
            {
                Id = 36,
                Address = "u222pdate地址" + DateTime.Now
            };
            db.StudentAddress.Attach(address);//Detached
      
            db.StudentAddress.Remove(address);//或将其状态修改为：EntityState.Deleted;
            db.SaveChanges();