无法将方法转换为商店表达式 [英] Can't translate method into a store expression

问题描述

与我发现的问题最接近的是这一个据我所知，这与同一问题无关.我可能会弄错了，在这种情况下，我希望有人能解释相似性的发展过程(除了相同的词指代错误).话虽如此，我有以下问题.

The closest to my questions that I've found is this one and as far I can see, it's not regarding the same issue. I might be mistaken, in which case, I hope someone can explain how the similarity goes (except for the same words referring to the error, that is). With that being said, I have the following issue.

这按预期工作.

List<Typo> things = context.Things.Where(thing => thing.Nice).ToList();

但是，不是.

List<Typo> things = context.Things.Where(thing => IsNice(thing)).ToList();
...
private bool IsNice(Typo thing) { return thing.Nice; }

上下文的类型为 ModelContainer ，派生 DbContext .有人告诉我这是EF的标准设置，我没有理由怀疑.该错误消息要求以下内容.

context is of type ModelContainer deriving DbContext. I've been told that it's a standard setup for EF and I have no reason to suspect otherwise. The error message claims the following.

{"LINQ to Entities无法识别XXX方法，并且该方法无法转换为商店表达式."}

{"LINQ to Entities does not recognize the method XXX method, and this method cannot be translated into a store expression."}

我没有这个错误的经验，坦率地说，我所做的研究几乎没有使我明白.我可以研究一下(a)以我的方式使它工作，并且(b)对其进行进一步调查.

I have no experience with this error and, frankly, the research I've made gave me very little clarity. What can I look into to (a) make it work my way and (b) investigate it further.

推荐答案

IMO，这仍然是您提到的问题:LINQ to Entities无法解释IsNice，因此，您需要普通" LINQ来解决Where方法.您可以使用AsEnumberable方法强制执行此操作:

IMO, it's still the same issue as the question you mention: LINQ to Entities cannot interpret IsNice, and thus, you need 'normal' LINQ to resolve the Where method. You can force this with the AsEnumberable method:

List<Typo> things = context.Things.AsEnumerable().Where(thing => IsNice(thing)).ToList();

或更短.

List<Typo> things = context.Things.Where(IsNice).ToList();

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