NHibernate- QueryOver 使用基类？

发布于 2024-10-14 18:45:53 字数 705 浏览 3 评论 0原文

现在我正在使用 Criteria API 并且很喜欢它，但如果我可以切换到 QueryOver API 那就更好了。但是，我的设置有点奇怪。为了将数据分区到表中，我有一个基本抽象类：

Listing

以及从该抽象类继承的许多类：

Listing_UK
Listing_US
etc.

使用条件 API，我可以执行以下操作：

Type t = typeof(Listing_UK);
if (condition) t = typeof(Listing_US);
DbSession.CreateCriteria(t)
            .Add(Restriction.Eq("field",value)
            .List<Listing>());

基本上，对不同的类使用相同的查询。似乎 QueryOver 的强类型本质阻止我这样做 - 基本问题是：

DBSession.QueryOver<Listing_UK>()

不转换为

DBSession.QueryOver<Listing>

虽然我明白为什么，但我想知道是否有人有任何可以用来创建通用 QueryOver 的技巧仍然会针对正确的表吗？

原文

Right now I'm using the Criteria API and loving it, but it would be even better if I could make the switch to the QueryOver API. However, my setup is a little strange. In order to partition data into tables, I have one base abstract class:

Listing

and a number of classes which inherit from that:

Listing_UK
Listing_US
etc.

With the criteria API, I can do something like:

Type t = typeof(Listing_UK);
if (condition) t = typeof(Listing_US);
DbSession.CreateCriteria(t)
            .Add(Restriction.Eq("field",value)
            .List<Listing>());

Basically, using the same query on different classes. It seems like the strongly-typed nature of QueryOver prevents me from doing this- the basic problem being that:

DBSession.QueryOver<Listing_UK>()

doesn't cast to

DBSession.QueryOver<Listing>

While I understand why, I'm wondering if anyone has any trick I could use to create a generic QueryOver that will still target the right table?

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猫性小仙女 2024-10-21 18:45:53

您可能会发现可以使用以下重载：

DbSession.CreateCriteria(myDynamicallyDeterminedType)
    .Add(Restrictions.On<Listing>(l => l.field == value))
    .List<Listing>();

You might find you could use the following overload:

DbSession.CreateCriteria(myDynamicallyDeterminedType)
    .Add(Restrictions.On<Listing>(l => l.field == value))
    .List<Listing>();

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七月上 2024-10-21 18:45:53

从技术上讲，这在某些情况下应该是允许的。即 c#4 中协方差的使用和一些反射。我相信所需的所有更改都是使 IQueryOver 接口协变。

subType = typeof(ParentClass).Assembly.GetType(subTypeFullName);

var mi = typeof(QueryOver).GetMethod("Of", new Type[]{});
var gmi = mi.MakeGenericMethod(subType);
var qo = (QueryOver<ParentClass, ParentClass>)gmi.Invoke(null, null);
var queryOver = qo.GetExecutableQueryOver(session);

// your comment restrictions/projections here.

我一直在思考这个想法，只要我们能够针对 .Net 4 进行构建，它就应该很容易工作。

Technically this should be allowable under certain circumstances. Namely the use of covariance in c#4 and some reflection. I believe that all the changes that would be needed would be to make the IQueryOver interfaces covariant.

subType = typeof(ParentClass).Assembly.GetType(subTypeFullName);

var mi = typeof(QueryOver).GetMethod("Of", new Type[]{});
var gmi = mi.MakeGenericMethod(subType);
var qo = (QueryOver<ParentClass, ParentClass>)gmi.Invoke(null, null);
var queryOver = qo.GetExecutableQueryOver(session);

// your comment restrictions/projections here.

I've wrestled with this idea and as long as we can build against .Net 4 it should work pretty easily.

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