NHibernate SQL查询在单列结果上的映射 [英] NHibernate SQL Query mapping on Single Column Result

问题描述

我有一个非常简单的问题，但找不到简单的答案.

I have a very simple question but cannot find a simple answer.

我让NHibernate执行一个原始SQL查询，不幸的是，该查询是从DB加载的(是的，我们将SQL查询存储在DB中，不是最好的设计，但请耐心等待).这意味着基本上我不知道查询将返回多少列. 我知道的是，如果查询是单个列，那么它就是我所需要的；如果查询不止一个列，那么我需要第一列，这很容易.

I have NHibernate executing a raw SQL query, which unfortunately is loaded from the DB (yes, we store SQL query in the DB, not the best design but bear with me). This means that basically I have no idea how many columns the query will return. What I know is that if the query is a single column then it is what I need and if it is more than one column then I need the first one, easy enough.

在我的代码中，我基本上有3个选择:

In my code I have basically 3 options:

session.CreateSQLQuery(SQLString).List();
session.CreateSQLQuery(SQLString).List<object>();
session.CreateSQLQuery(SQLString).List<object[]>();

问题在于，如果查询返回单列，则List()将返回List<int>(或适当的类型，但对于我而言应为int)；如果我返回多列，则将返回List<object[]>(). List<object>也一样，除了在这种情况下不会返回List<int>. 当然，尝试始终强制转换为object [](第三个选项)并获取第一个元素是行不通的，因为nHibernate返回一个int且不能强制转换为object [].

Problem is that the List() will return either a List<int> (or the appropriate type, but int should be in my case) if the query returns a single column, or a List<object[]>() if I have multiple columns. Same goes for List<object> except that it will not return a List<int> in this case. Of course trying to always cast to object[] (3rd option) and get the first element does not work, since nHibernate returns an int and that cannot be cast to object[].

是否有一种方法可以强制nHibernate即使在单列情况下也总是返回object []?如果不是，是否有一种简便的方法来检查结果中的列数并采取相应的措施?

Is there a way to force nHibernate to always return an object[] even in the case of a single column? If not, is there an easy way to check the number of columns in the result and act accordingly?

谢谢！

推荐答案

您应该看看NHibernate提供的不同结果转换器(当然，您也可以编写自己的代码).

You should take a look at the differant result transformers NHibernate provides out of the box (you can write your own as well of course).

NHibernate.Transform.ToListResultTransformer可能适合您的情况. AFAIK，它将您的结果转换为一个IList，其中每个条目再次包含一个IList.

What might fit in your case would be the NHibernate.Transform.ToListResultTransformer. AFAIK, it transforms your result to an IList, where each entry contains an IList again.

所以:

IList items = session
.CreateSQLQuery(query)
.SetResultTransformer(new NHibernate.Transform.ToListResultTransformer())
.List()

if(((Ilist)items[0]).Count == 1)
// just one columns
else
// more columns or zero

这篇关于NHibernate SQL查询在单列结果上的映射的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！