Conditional symbols doesn't work

Question

I have a class library contains the following code snippet:

#if (DEBUG && CLOUD)
    return "DEBUG && CLOUD";
#elif (DEBUG && !CLOUD)
    return "DEBUG";
#else
    return "Release";
#endif

When I reference this library into my application I got only DEBUG or Release as returns, even if CLOUD is defined.

Answer 1

The behavior is so weird, so I went to the solution properties, under the configuration properties tab. I shocked by what Visual Studio do.

Answer 2

Case #1:

#define DEBUG 1
#define CLOUD 1

--> return "DEBUG && CLOUD";

Case #2:

#define DEBUG
#define CLOUD

--> return "Release";

From this example one can learn that #if (cond) evaluates a numeric condition.

If you want to check for definition only you should do:

#if defined DEBUG && defined CLOUD