Question

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

---

i know C# has a Conditional attribute:

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

which is equivalent¹ to:

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

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

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

Which leads me to try:

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

which doesn’t compile. And:

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

which doesn’t compile. And:

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

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

¹ Not true, but true enough. Don’t make me bring back the Nitpicker’s Corner.

Answer 1

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

ShowDebugString(MethodThatTakesAges());

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

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 🙂

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