C＃！Conditional属性？ [英] C# !Conditional attribute?

问题描述

C＃有一个的不的条件（！条件， NotConditional ，条件（！））的属性？

Does C# have a not Conditional (!Conditional, NotConditional, Conditional(!)) attribute?

我知道C＃有一个条件属性：

i know C# has a Conditional attribute:

[Conditional("ShowDebugString")]
public static void ShowDebugString(string s)
{
   ...
}

这相当于 ¹ 到

public static void ShowDebugString(string s)
{
#if ShowDebugString
   ...
#endif
}

但在这种情况下，我想的逆的行为（你有专门的退出的）：

But in this case i want the inverse behavior (you have to specifically opt out):

public static void ShowDebugString(string s)
{
#if !RemoveSDS
   ...
#endif
}

这使我尝试：

[!Conditional("RemoveSDS")]
public static void ShowDebugString(string s)
{
   ...
}

不编译。和：

[Conditional("!RemoveSDS")]
public static void ShowDebugString(string s)
{
   ...
}

不编译。和：

[NotConditional("RemoveSDS")]
public static void ShowDebugString(string s)
{
   ...
}

不编译，因为这只是一厢情愿的想法。

which doesn't compile because it's only wishful thinking.

¹ 不是真的，但足够真实。不要让我带回了都舍不得亏的园地。

推荐答案

首先，具有条件属性的不的等价于有＃如果而不是方法。试想一下：

First, having the Conditional attribute is not equivalent to having #if instead the method. Consider:

ShowDebugString(MethodThatTakesAges());

随着 ConditionalAttribute ， MethodThatTakesAges 不会被调用真正的行为 - 在整个呼叫的包括参数评测的从编译器中删除。

With the real behaviour of ConditionalAttribute, MethodThatTakesAges doesn't get called - the entire call including argument evaluation is removed from the compiler.

当然的另一点是，它依赖于编译时preprocessor符号在主叫的的编译时间，而不是的方法的:)

Of course the other point is that it depends on the compile-time preprocessor symbols at the compile time of the caller, not of the method :)

但是，没有，我不相信有什么事该做你想要的这里。我刚刚检查了C＃规范第17.4.2它与条件方法和条件属性类的交易，并没有什么在那里暗示有任何这样的机制。

But no, I don't believe there's anything which does what you want here. I've just checked the C# spec section 17.4.2 which deals with conditional methods and conditional attribute classes, and there's nothing in there suggesting there's any such mechanism.

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