Question

I am following a tutorial that has this code:

    static void Main()
    {
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        int i = 1;
        while (true)
        {
#if TEST
            if (i % 2 == 0)
            continue;
#endif
            i++;
            Console.WriteLine("The value of i is {0}", i);
            if (i > 9)
                break;
            }
            Console.WriteLine("The value of i is {0}", i);

            Application.Run(new Form1());
        }

What is the purpose of using #if TEST instead of just if(TEST)?

Answer 1

It’s useful when you need two (or more) versions of your code with little difference. Then instead of keeping two projects using complier directives like #if TEST you write both versions in the same project. Then from project properties you can set value for TEST llike TEST = true and then compile the project.

#if TEST
    Console.WriteLine("Hello World!");
#else
    Console.WriteLine("Goodbye World!");
#endif 

If TEST = true it’s like you just write : Console.WriteLine("Hello World!"); and vice versa.