At BataviaLabs we were debating coding guidelines the other day and came across this one: do you use #if or the ConditionalAttribute to indicate to the compiler if a method should be compiled. Let me elaborate...

If you have a method you only want to compile in a debug scenario, you have the following options:

1) Use #if DEBUG as shown below

class Program
{
    static void Main(string[] args)
    {
#if DEBUG
        SomeMethod();
#endif
        Console.WriteLine("End");
        Console.ReadKey();
    }

#if DEBUG
    internal static void SomeMethod()
    {
        Console.WriteLine("SomeMethod");
    }
#endif
}

2) Use the ConditionalAttribute as shown below

class Program
{
    static void Main(string[] args)
    {
        SomeMethod();
        Console.WriteLine("End");
        Console.ReadKey();
    }

    [Conditional("DEBUG")]
    internal static void SomeMethod()
    {
        Console.WriteLine("SomeMethod");
    }
}

The difference between these two methods is enormous. The first sample is very explicit. Any code you don't want to compile into the production build is placed between #if DEBUG and #endif. If you try to call SomeMethod in a production build, the compiler will give you a compile error. The ConditionalAttributeon the other hand doesn't require you to remove the calls to SomeMethod. If a method is marked [Conditional], any calls made to that method are removed from the build by the compiler. A proviso here is that [Conditional] only works with methods that don't return a value (i.e. void).

I much more prefer #if DEBUG, because it is explicit. I can't run into a situation where from reading the code I'm thinking "SomeMethod is being executed", but it actually isn't because the compiler removed the call. Comments anyone?