Csharp/CSharp Tutorial/Preprocessing Directives/define

A list of preprocessor commands available in C#:

<source lang="csharp">#define

1. undef
2. if
3. else
4. elif
5. endif
6. line
7. error
8. warning
9. region

1. pragma</source>

Preprocessing Directives: define

1. The #define directive defines a character sequence called a symbol.
2. The existence or nonexistence of a symbol can be determined by #if or #elif

The general form for #define:

<source lang="csharp">#define symbol</source>

Use a symbol expression.

<source lang="csharp">#define AAA

1. define BBB

using System;

class MainClass {

 public static void Main() { 
    
   #if AAA 
     Console.WriteLine("Compiled for AAA version."); 
   #endif 

   #if AAA && BBB 
      Console.Error.WriteLine("Testing 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.

Use the Conditional attribute with define

<source lang="csharp">#define USE_METHOD_1 using System; using System.Diagnostics; class MainClass {

 [Conditional("USE_METHOD_1")]
 public static void Method1()
 {
   Console.WriteLine("In Method 1");
 }
 public static void Main() 
 {
     Console.WriteLine("In Main");
   Method1();
 }

}</source>

In Main
In Method 1