/define:name[;name2]
where:
The /define option defines name as a symbol in your program. It has the same effect as using a #define preprocessor directive in your source file. A symbol remains defined until an #undef directive in the source file removes the definition or the compiler reaches the end of the file.
You can use symbols created by this option with #if, #else, #elif, and #endif to compile source files conditionally.
/d is the short form of /define.
You can define multiple symbols with /define by using a semicolon or comma to separate symbol names. For example:
/define:DEBUG;TUESDAY
// compile with /define:xx or uncomment the next line // #define xx using System; public class Test { public static void Main() { #if (xx) Console.WriteLine("xx exists"); #else Console.WriteLine("xx does not exist"); #endif } }