Csharp/CSharp Tutorial/Preprocessing Directives/if

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Demonstrate #else.

<source lang="csharp">#define AAA

  1. 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."); 
 } 

}</source>

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


<source lang="csharp">#if symbol-expression

     statement sequence 
   #endif</source>