Csharp/C Sharp/Language Basics/Preprocessor Directives

#define, #if, and #endif preprocessor directives

<source lang="csharp"> /* Mastering Visual C# .NET by Jason Price, Mike Gunderloy Publisher: Sybex; ISBN: 0782129110

• /

/*

 Example4_16.cs illustrates the use of the
 #define, #if, and #endif preprocessor directives

• /

1. define DEBUG

public class Example4_16 {

 public static void Main()
 {
   int total = 0;
   int counter = 0;
   myLabel:
   counter++;
   total += counter;
   System.Console.WriteLine("counter = " + counter);
   if (counter < 5)
   {

1. if DEBUG

     System.Console.WriteLine("goto myLabel");

1. endif

     goto myLabel;
   }
   System.Console.WriteLine("total = " + total);
 }

}

      </source>

Demonstrate #elif

<source lang="csharp"> /* C#: The Complete Reference by Herbert Schildt Publisher: Osborne/McGraw-Hill (March 8, 2002) ISBN: 0072134852

• /

// Demonstrate #elif.

1. define RELEASE

using System;

public class Test5 {

 public static void Main() { 
    
   #if EXPERIMENTAL 
     Console.WriteLine("Compiled for experimental version."); 
   #elif RELEASE 
     Console.WriteLine("Compiled for release."); 
   #else 
     Console.WriteLine("Compiled for internal testing."); 
   #endif 

   #if TRIAL && !RELEASE 
      Console.WriteLine("Trial version."); 
   #endif 
  
   Console.WriteLine("This is in all versions."); 
 } 

}

      </source>

Demonstrate #else

<source lang="csharp"> /* C#: The Complete Reference by Herbert Schildt Publisher: Osborne/McGraw-Hill (March 8, 2002) ISBN: 0072134852

• /

// Demonstrate #else.

1. define EXPERIMENTAL

using System;

public class Test4 {

 public static void Main() { 
    
   #if EXPERIMENTAL 
     Console.WriteLine("Compiled for experimental version."); 
   #else 
     Console.WriteLine("Compiled for release."); 
   #endif 

   #if EXPERIMENTAL && TRIAL 
      Console.Error.WriteLine("Testing experimental trial version."); 
   #else 
      Console.Error.WriteLine("Not experimental trial version."); 
   #endif 
  
   Console.WriteLine("This is in all versions."); 
 } 

}

      </source>

Demonstrate #if, #endif, and #define

<source lang="csharp"> /* C#: The Complete Reference by Herbert Schildt Publisher: Osborne/McGraw-Hill (March 8, 2002) ISBN: 0072134852

• /

// Demonstrate #if, #endif, and #define.

1. define EXPERIMENTAL

using System;

public class Test1 {

 public static void Main() { 
    
   #if EXPERIMENTAL 
     Console.WriteLine("Compiled for experimental version."); 
   #endif 
  
   Console.WriteLine("This is in all versions."); 
 } 

}

      </source>

Demonstrates the use of a conditional method

<source lang="csharp"> /* C# Programming Tips & Techniques by Charles Wright, Kris Jamsa Publisher: Osborne/McGraw-Hill (December 28, 2001) ISBN: 0072193794

• /

// CondMeth.cs -- demonstrates the use of a conditional method // // Compile this program with the following command line: // C:>csc CondMeth.cs //

1. define MY_CONDITION

using System; using System.Diagnostics; namespace nsConditional {

   public class CondMeth
   {
       static public void Main ()
       {
           clsTest test = new clsTest(42);
           test.ShowValue ();
       }
   }
   class clsTest
   {
       public clsTest (int num)
       {
           m_Num = num;
       }
       int m_Num;
       [Conditional("MY_CONDITION")]
       public void ShowValue()
       {
           if (m_Num < 50)
           {
               Console.WriteLine (m_Num + " is less than 50");
           }
       }
   }

}

      </source>

line number

<source lang="csharp"> using System; class Operators {

   static void Main() {

1. line 300
2. warning Something happened.
3. warning Something else happened.
4. line 400 "someotherfile.cs"
5. warning Something happened later.
6. line default
7. warning Nothing else will happen.

   }

}

</source>

precompile marco: define, undef, elif, endif

<source lang="csharp">

1. define MYOWN
2. define DEBUG
3. undef VERBOSE

using System; class Operators {

   static void Main() {

1. if MYOWN

       Console.WriteLine("Hi!");

1. elif VERBOSE

  Console.WriteLine("Program Starting?);

1. endif

       int a = 10, b = 5;

1. if DEBUG

       Console.WriteLine("a={0}, b={1}", a, b);

1. endif
2. if MYOWN && (VERBOSE || DEBUG)

       Console.WriteLine("Continuing, Author");

1. elif !MYOWN && (VERBOSE || DEBUG)

  Console.WriteLine("Continuing?);

1. endif

   }

}

</source>

Preprocessor 2

<source lang="csharp"> /* C# Programming Tips & Techniques by Charles Wright, Kris Jamsa Publisher: Osborne/McGraw-Hill (December 28, 2001) ISBN: 0072193794

• /

namespace nsPreProc {

   using System;
   public class PreProc
   {
       static public void Main()
       {

1. if ALTMAIN
2. warning Compiling alternate statement

           Console.WriteLine ("Using alternate Main()");

1. elif OTHERMAIN
2. warning Compiling other statement

           Console.WriteLine ("Using other Main()");

1. else
2. warning Compiling main

           Console.WriteLine ("Using Main()");

1. endif

       }

1. line 200
2. if SHOWERROR

       int iVar;

1. error This is line 23 but the error report should show line 202
2. endif

   }

}

      </source>

#undef, #elif, and #else preprocessor directives

<source lang="csharp"> /* Mastering Visual C# .NET by Jason Price, Mike Gunderloy Publisher: Sybex; ISBN: 0782129110

• /

/*

 Example4_17.cs illustrates the use of the
 #undef, #elif, and #else preprocessor directives

• /

1. define DEBUG
2. undef DEBUG
3. define PRODUCTION

public class Example4_17 {

 public static void Main()
 {
   int total = 0;
   int counter = 0;
   myLabel:
   counter++;
   total += counter;
   System.Console.WriteLine("counter = " + counter);
   if (counter < 5)
   {

1. if DEBUG

     System.Console.WriteLine("goto myLabel");

1. elif PRODUCTION

     System.Console.WriteLine("counter < 5");

1. else

     System.Console.WriteLine("goto myLabel, counter < 5");

1. endif

     goto myLabel;
   }
   System.Console.WriteLine("total = " + total);
 }

}

      </source>

#undef Marco

<source lang="csharp">

1. define MYOWN
2. define DEBUG
3. undef VERBOSE
4. define PROGRAMMER_IS_BRIAN
5. undef PROGRAMMER_IS_DAVE

using System; class Preprocessor {

   static void Main() {

1. if MYOWN

       Console.WriteLine("Hi Author!");

1. elif VERBOSE

  Console.WriteLine("Program Starting?);

1. endif

       int a = 10, b = 5;

1. if DEBUG

       Console.WriteLine("a={0}, b={1}", a, b);

1. endif
2. if MYOWN && (VERBOSE || DEBUG)

       Console.WriteLine("Continuing, Author");

1. elif !MYOWN && (VERBOSE || DEBUG)

  Console.WriteLine("Continuing?);

1. endif
2. if PROGRAMMER_IS_BRIAN || PROGRAMMER_IS_DAVE
3. warning Execution may vary depending on programmer.
4. endif
5. if PROGRAMMER_IS_DAVE
6. error Something you did broke this code.
7. endif

   }

}

</source>

Use a symbol expression

<source lang="csharp"> /* C#: The Complete Reference by Herbert Schildt Publisher: Osborne/McGraw-Hill (March 8, 2002) ISBN: 0072134852

• /

// Use a symbol expression.

1. define EXPERIMENTAL
2. define TRIAL

using System;

public class Test2 {

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

   #if EXPERIMENTAL && TRIAL 
      Console.Error.WriteLine("Testing experimental trial version."); 
   #endif 
  
   Console.WriteLine("This is in all versions."); 
 } 

}

      </source>

Use marco to define flag variable

<source lang="csharp">

1. define DEBUGGING

using System; class Starter {

1. if DEBUGGING

   static void OutputLocals() {
       Console.WriteLine("debugging...");
   }

1. endif

   static void Main() {

1. if DEBUGGING

       OutputLocals();

1. endif

   }

}

</source>