nHibernate无法将布尔值转换为字符串 [英] nHibernate unable to cast Boolean to String

问题描述

我有以下查询:

var query = from item in Session.Query<FactuurItem>()
    where item.EnergieType == etype
    && (item.DienstType == null || item.DienstType == DienstType.Onbekend || item.DienstType == dtype)
    && item.IsActive == true
    orderby item.Naam
    select item;

将转换为以下SQL:

select * from [FactuurItem] factuurite0_ 
where 
    factuurite0_.EnergieType=? 
    and (factuurite0_.DienstType is null or factuurite0_.DienstType=? or factuurite0_.DienstType=?) 
    and case when factuurite0_.IsActive=1 then 'true' else 'false' end=case when ?='true' then 'true' else 'false' end 
order by factuurite0_.Naam asc

哪个会导致异常:

{"Unable to cast object of type 'System.Boolean' to type 'System.String'."}

现在我的问题是:为什么?

Now for my question: why??

原始查询对我来说没问题.但是，SQL没有.这两个案例陈述从何而来?显然，它尝试将属性IsActive转换为SQL中的字符串，但这样做没有成功.

The original query looks ok to me. The SQL, however, does not. Where do the two case-statements originate from? Apparently it tries to convert the property IsActive to a string in SQL, which it fails to do.

编辑

好，找到解决方案.映射等没有问题，只是LINQ查询如何转换为SQL.特别是，该行的翻译方式:

Ok, found the solution. Nothing wrong with mapping etc., just with how the LINQ query is translated to SQL. In particular, how this line is translated:

&& item.IsActive == true

以某种方式，这被转换为复杂的CASE语句，最终导致异常消息.但是，== true部分不是真正必要的.通过删除它，翻译器不再感到困惑，并提供了正确的SQL:

Somehow, this gets translated into the complex CASE-statement which ultimately results in the exception message. However, the == true-part isn't really necessary. By removing it, the translator no longer gets confused and provides the proper SQL:

factuurite0_.IsActive=1

没有更多的案例说明，也没有更多的例外.

No more CASE-statement and no more exception.

推荐答案

好，找到了解决方案.映射等没有问题，只是LINQ查询如何转换为SQL.特别是，该行的翻译方式:

Ok, found the solution. Nothing wrong with mapping etc., just with how the LINQ query is translated to SQL. In particular, how this line is translated:

&& item.IsActive == true

以某种方式，这被转换为复杂的CASE语句，最终导致异常消息.但是，== true部分不是真正必要的.通过删除它，翻译器不再感到困惑，并提供了正确的SQL:

Somehow, this gets translated into the complex CASE-statement which ultimately results in the exception message. However, the == true-part isn't really necessary. By removing it, the translator no longer gets confused and provides the proper SQL:

factuurite0_.IsActive=1

没有更多的案例说明，也没有更多的例外.

No more CASE-statement and no more exception.

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