实体框架/SQL2008 - 如何自动更新实体的 LastModified 字段? [英] Entity Framework/SQL2008 - How to Automatically Update LastModified fields for Entities?
问题描述
如果我有以下实体:
public class PocoWithDates
{
public string PocoName { get; set; }
public DateTime CreatedOn { get; set; }
public DateTime LastModified { get; set; }
}
哪个对应于具有相同名称/属性的 SQL Server 2008 表...
Which corresponds to a SQL Server 2008 table with the same name/attributes...
我如何自动:
- 将记录的 CreatedOn/LastModified 字段设置为now(在执行 INSERT 时)
- 将记录的 LastModified 字段设置为 now(执行 UPDATE 时)
- Set the CreatedOn/LastModified field for the record to now (when doing INSERT)
- Set the LastModified field for the record to now (when doing UPDATE)
当我说自动时,我的意思是我希望能够做到这一点:
When i say automatically, i mean i want to be able to do this:
poco.Name = "Changing the name";
repository.Save();
不是这个:
poco.Name = "Changing the name";
poco.LastModified = DateTime.Now;
repository.Save();
在幕后,某事"应该自动更新日期时间字段.那是什么东西"?
Behind the scenes, "something" should automatically update the datetime fields. What is that "something"?
我正在使用 Entity Framework 4.0 - EF 是否可以自动为我执行此操作?(也许是 EDMX 中的特殊设置?)
I'm using Entity Framework 4.0 - is there a way that EF can do that automatically for me? (a special setting in the EDMX maybe?)
从 SQL Server 端,我可以使用 DefaultValue,但这仅适用于 INSERT 的(不是 UPDATE 的).
From the SQL Server side, i can use DefaultValue, but that will only work for INSERT's (not UPDATE's).
同样,我可以使用 POCO 上的构造函数设置默认值,但这同样仅在实例化对象时有效.
Similarly, i can set a default value using a constructor on the POCO's, but again this will only work when instantiating the object.
当然我可以使用触发器,但它并不理想.
And of course i could use Triggers, but it's not ideal.
因为我使用的是实体框架,所以我可以连接到 SavingChanges 事件并在这里更新日期字段,但问题是我需要意识到"POCO(目前,我的存储库是用泛型实现的).我需要做一些面向对象的技巧(比如让我的 POCO 实现一个接口,然后调用一个方法).我并不反对,但如果我必须这样做,我宁愿手动设置字段.
Because i'm using Entity Framework, i can hook into the SavingChanges event and update the date fields here, but the problem is i need to become "aware" of the POCO's (at the moment, my repository is implemented with generics). I would need to do some sort of OO trickery (like make my POCO's implement an interface, and call a method on that). I'm not adversed to that, but if i have to do that, i would rather manually set the fields.
我主要是在寻找 SQL Server 2008 或 Entity Framework 4.0 解决方案.(或智能 .NET 方式)
I'm basically looking for a SQL Server 2008 or Entity Framework 4.0 solution. (or a smart .NET way)
有什么想法吗?
编辑
感谢@marc_s 的回答,但我选择了一个更适合我的场景的解决方案.
Thanks to @marc_s for his answer, but i went with a solution which is better for my scenario.
推荐答案
因为我有一个服务层在我的控制器(我使用 ASP.NET MVC)和我的存储库之间进行调解,所以我决定在这里自动设置字段.
As i have a service layer mediating between my controllers (im using ASP.NET MVC), and my repository, i have decided to auto-set the fields here.
此外,我的 POCO 没有关系/抽象,它们是完全独立的.我想保持这种方式,不标记任何虚拟属性,也不创建基类.
Also, my POCO's have no relationships/abstractions, they are completely independant. I would like to keep it this way, and not mark any virtual properties, or create base classes.
所以我创建了一个接口,IAutoGenerateDateFields:
So i created an interface, IAutoGenerateDateFields:
public interface IAutoGenerateDateFields
{
DateTime LastModified { get;set; }
DateTime CreatedOn { get;set; }
}
对于我希望自动生成这些字段的任何 POCO,我实现了这个接口.
For any POCO's i wish to auto-generate these fields, i implement this inteface.
使用我的问题中的示例:
Using the example in my question:
public class PocoWithDates : IAutoGenerateDateFields
{
public string PocoName { get; set; }
public DateTime CreatedOn { get; set; }
public DateTime LastModified { get; set; }
}
在我的服务层,我现在检查具体对象是否实现了接口:
In my service layer, i now check if the concrete object implements the interface:
public void Add(SomePoco poco)
{
var autoDateFieldsPoco = poco as IAutoGenerateDateFields; // returns null if it's not.
if (autoDateFieldsPoco != null) // if it implements interface
{
autoDateFieldsPoco.LastModified = DateTime.Now;
autoDateFieldsPoco.CreatedOn = DateTime.Now;
}
// ..go on about other persistence work.
}
稍后我可能会在 Add out to a helper/extension 方法中破坏该代码.
I will probably break that code in the Add out to a helper/extension method later on.
但我认为这对我的场景来说是一个不错的解决方案,因为我不想在保存时使用虚拟(因为我使用的是工作单元、存储库和纯 POCO),并且不想使用触发器.
But i think this is a decent solution for my scenario, as i dont want to use virtuals on the Save (as i'm using Unit of Work, Repository, and Pure POCO's), and don't want to use triggers.
如果您有任何想法/建议,请告诉我.
If you have any thoughts/suggestions, let me know.
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