C# Error CS1517 – Invalid preprocessor expression

C# Error

CS1517 – Invalid preprocessor expression

Reason for the Error & Solution

Invalid preprocessor expression

The compiler encountered an invalid preprocessor expression.

For more information, see .

The following sample shows some valid and invalid preprocessor expressions:

// CS1517.cs  
#if symbol      // OK  
#endif  
#if !symbol     // OK  
#endif  
#if (symbol)    // OK  
#endif  
#if true        // OK  
#endif  
#if false       // OK  
#endif  
#if 1           // CS1517  
#endif  
#if ~symbol     // CS1517  
#endif  
#if *           // CS1517  
#endif  
  
class x  
{  
   public static void Main()  
   {  
   }  
}