In Razor compiler directives do not work, cause Razor Views are not compiled.
So this would not work:

@{ #if DEBUG}

@{#else}

@{#endif}

But you can trick that thing into submission, thanks to this StackOverflow topic

A better, more generic solution is to use an extension method, so all views have access to it:

public static bool IsReleaseBuild()
{
#if DEBUG
    return false;
#else
    return true;
#endif
}

You can then use it like follows in any view (razor syntax):

@if(IsReleaseBuild())