如何在单元测试期间重写 IQueryable 的 Contains 方法？
事情是这样的：我正在测试一个使用 LINQ to Entities (EF4/.NET4) 的应用程序。该应用程序绑定到 Contains 方法的实现，该方法忽略空值，并且由于数据库的配置方式，忽略大小写。效果很好。
但是，当我从单元测试中调用相同的方法时，我传递了一个假上下文，该上下文通过 IQueryable 的内存中实现公开集合。在本例中，引入的是 Contains 的 LINQ to Objects 版本，并且关心 null 和大小写。
现在，我可以编写应用程序代码来检查 null 和大小写，但我不想影响正在生成的 SQL，以便在从单元测试调用它并且不涉及 SQL 时它可以工作。
我真正想要的是提供正确的 IQueryable 或其他任何内容，以便在测试期间，我可以交换我自己的自定义 Contains 实现，该实现忽略 null 和大小写。我该怎么做？谢谢！
So here's the thing: I've got an app that I'm testing that uses LINQ to Entities (EF4/.NET4). The app binds to an implementation of the Contains method that ignores nulls and, due to the way the database is configured, ignores case. That works great.
However, when I call into the same methods from my unit tests, I'm passing in a fake context which exposes collections with an in-memory implementation of IQueryable. In this case, it's the LINQ to Objects version of Contains that gets brought in and that one cares about null and case.
Now, I could write my application code to check for null and case, but I don't want to affect the SQL that's being generated just so it will work when it's being called from a unit test and SQL is not involved.
What I really want is to provide the correct IQueryable or whatever so that, during a test, I can swap in my own custom Contains implementation that ignores null and case. How do I do that? Thanks!
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编译器将绑定到最派生的编译时类型的扩展方法。
即使您传递一个模拟实例并在单元测试上下文中对其类型有一个“Contains”扩展方法的自定义实现，您调用的一些代码只知道您提供了一个 IQueriable 实例，因此它绑定到 linq to objects 版本。
也许你可以通过 实现您自己的 QueryProvider 但这似乎是一个极端的选择。
如果您可以使用 C#4.0 动态类型，也许还有另一种方法。
Compiler will bind to the most derived compile-time type's exthension method.
Even if you pass a mock instance and have a custom implementation of "Contains" extension method to its type on your Unit Test context, you are calling some code that only knows that you provided an IQueriable instance, so it binds to linq to objects version.
Probably you can achieve this by implementing your own QueryProvider but it seems to be an extreme option.
Maybe there is another way if you can use C#4.0 dynamic types.
如果您有一个假上下文，您不能创建一个模拟的 IQueriable 并使用它吗？
If you have a fake context, can't you create a mock
IQueriableand use that?