Running different codes between debug mode and release mode

This is one of the compiler feature that is not widely used or not known by most of the programmers. For example, in ASP.net, you might want to use the full Java Script file in the debug mode. But, in the release mode, you might want to include the "light" version (or minified version). This is because the minified version requires lesser time for the browser to download it.

public void IncludeScript()
{
    Page pg = HttpContext.Current.Handler as Page;
    string js_url;
    string key = "jquery";

    if (!pg.ClientScript.IsClientScriptIncludeRegistered(key))
    {
#if DEBUG
       // for debug mode, include the full JavaScript.
        js_url = pg.ResolveUrl("~/js/jquery-1.7.1.js");
#else
       // for release mode, include the minified version.
        js_url = pg.ResolveUrl("~/js/jquery-1.7.1.min.js");
#endif

        pg.ClientScript.RegisterClientScriptInclude(pg.GetType(),
                                                    key,
                                                    js_url);
    }
}

Other situation where you might want to use this concept:

• Set the default user name and password in debug mode.
• Get and/or save the runtime value in debug mode.
• Create a debug log while debugging the program.
• Modifying or setting variable's value at debugging time.

Please take note that the compiler directive does not limit to ASP.net. It is meant for all kinds of project types.