NHibernate 查询映射集合
在我的 ASP.NET Web 应用程序中，我使用 NHibernate 来保存我的“用户”实例，其中每个实例都有一个“条目”集合。这是典型的一对多映射，并且工作得很好。条目的映射代码如下所示：
<bag name="Entries" cascade="all-delete-orphan">
<key column="UserID" />
<one-to-many class="MyApp.Entities.Entry, MyApp.Entities" />
</bag>
现在我有一个页面，我想在其中显示包含登录用户的所有条目的网格。为此，我可以简单地将当前用户的“Entries”属性绑定到网格“DataSource”属性。这也工作得很好，但这也意味着网格内置分页功能（Telerik RadGrid）对数据库性能没有任何影响，因为每次显示网格时都会加载所有条目。
因此，我可以应用自定义分页，只获取显示网格当前页面所需的行。典型的 Linq2NHibernate 查询如下所示：
var query = from entry in Session.Linq<Entry>()
where entry.User == currentUser
select entry;
query.Skip(pageNum * pageSize).Take(pageSize).ToList();
使用这种方法，我需要扩展我的存储库，尽管 NHibernate 已经完成了 User 和 Entry 之间的映射...
我的问题是：如果我使用 LINQ 直接查询我的“Entries”集合“用户”对象 - 这是否意味着所有条目都将从数据库加载，然后在内存中过滤，或者将其转换为真正的“数据库”查询，以便我可以使用这种更舒适的方法来实施分页？
示例：
myGrid.DataSource = currentUser.Entries.Skip(pageNum * pageSize).Take(pageSize).ToList();
J4I：当然，我在映射文件中使用延迟加载...
提前谢谢您！
In my ASP.NET web-application I use NHibernate to persist my "User"-Instances, where each of them has a "Entries" - collection. It is a typical one-to-many mapping and it works just fine. The mapping-code for the entries looks like this:
<bag name="Entries" cascade="all-delete-orphan">
<key column="UserID" />
<one-to-many class="MyApp.Entities.Entry, MyApp.Entities" />
</bag>
Now I have a page, where I want to display a grid with all the entries of the logged-in user. To do so, I could simply bind the "Entries" property of the current user to the Grids "DataSource" - property. This also works just fine, but this also means, that the grids built-in paging-functionality (Telerik RadGrid) doesn't have any effect on database-performance, because all the entries will be loaded each time when displaying the grid.
Therefore I could apply my custom-paging, where I only fetch the rows which I need to display the grids current page. A typical Linq2NHibernate query looks like this:
var query = from entry in Session.Linq<Entry>()
where entry.User == currentUser
select entry;
query.Skip(pageNum * pageSize).Take(pageSize).ToList();
Using this approach I need to extend my repository altough NHibernate has already done the mapping between User and Entry...
My question is: If I use LINQ to directly query the "Entries"-collection of my "User"-object - does this mean, that all the Entries will be loaded from the database and then filtered in memory or would this be translated to a real "database"-query, so that I could use this much more comfortable approach to implement paging?
Example:
myGrid.DataSource = currentUser.Entries.Skip(pageNum * pageSize).Take(pageSize).ToList();
J4I: Of course I use lazy-loading in the mapping files...
Thank you in advance!
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集合上的 LINQ 将始终是 LINQ 到对象，因为它们不实现 IQueryable，因此您将在内存中加载所有内容。
查询是目前唯一可能的方法。
LINQ on the collection will always be LINQ-to-objects, as they don't implement IQueryable, so you'd be loading everything in memory.
A query is the only possible approach at this moment.