Csharp/CSharp Tutorial/Preprocessing Directives/if

Demonstrate #else.

#define AAA 
#define BBB 
 
using System; 
 
class Test { 
  public static void Main() { 
     
    #if AAA 
      Console.WriteLine("Compiled for AAA version."); 
    #else 
      Console.WriteLine("Compiled for release."); 
    #endif 
 
    #if AAA && BBB 
       Console.Error.WriteLine("Testing AAA and BBB version."); 
    #else 
       Console.Error.WriteLine("Not (AAA and BBB) version."); 
    #endif 
   
    Console.WriteLine("This is in all versions."); 
  } 
}

Compiled for AAA version.
Testing AAA and BBB version.
This is in all versions.

Demonstrate #if, #endif, and #define.

1. The #if and #endif directives enable conditional compilation.
2. A symbol is true if it has been defined.
3. A symbol is false if it has not been defined.
4. If a symbol has been defined by a #define directive, the symbol true.

The general form of #if is

#if symbol-expression
      statement sequence 
    #endif