How do you use #define?

Question

I'm wondering about instances when it makes sent to use #define and #if statements. I've known about it for a while, but never incorporated it into my way of coding. How exactly does this affect the compilation?

Is #define the only thing that determines if the code is included when compiled? If I have #define DEBUGme as a custom symbol, the only way to exclude it from compile is to remove this #define statement?

Answer 1

In C# #define macros, like some of Bernard's examples, are not allowed. The only common use of #define/#ifs in C# is for adding optional debug only code. For example:

        static void Main(string[] args)
        {
#if DEBUG
            //this only compiles if in DEBUG
            Console.WriteLine("DEBUG")
#endif 
#if !DEBUG
            //this only compiles if not in DEBUG
            Console.WriteLine("RELEASE")
#endif
            //This always compiles
            Console.ReadLine()
        }