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Categories / C# Tutorial / Preprocessing Directives

 

Use #define and #undef to control the program logic

The #undef directive removes a previously defined definition. The #undef directive "undefines" a symbol. The general form for #undef is #undef symbol #define win2000 #define release #undef  win98 using System; using System.Diagnostics; class MainClass {     public static void Main()     {         string platformName;         #if winXP       // Compiling for Windows XP             platformName = "Microsoft Windows XP";         #elif win2000   // Compiling for Windows 2000             platformName = "Microsoft Windows 2000";         #elif winNT     // Compiling for Windows NT             platformName = "Microsoft Windows NT";         #elif win98     // Compiling for Windows 98             platformName = "Microsoft Windows 98";         #else           // Unknown platform specified             platformName = "Unknown";         #endif         Console.WriteLine(platformName);     } } Microsoft Windows 2000