#500 – #define and #undef Must Be at Top of File

In C#, all #define and #undef  preprocessor directives must appear at the top of a source code file, i.e. before any valid C# tokens.  The definition (or un-definition) then remains in effect until the end of the file is reached.

#define QUIET

using System;
using DogLibrary;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main()
        {
            Dog d1 = new Dog("Kirby", 12);
#if QUIET
            d1.Bark("Arf");
#else
            d1.bark("WOOOF");
#endif
        }
    }
}

In this case, because the conditional compilation symbol is included directly in the code, Intellisense already knows which of the two Bark methods will be included in the code.  It displays the line that will not be compiled in grey.

In this example, the second Bark method is not compiled at all.

 

Advertisements

About Sean
Software developer in the Twin Cities area, passionate about .NET technologies. Equally passionate about my own personal projects related to family history and preservation of family stories and photos.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: