GTKD - get CSS class for button

[TheDGuy via Digitalmars-d-learn]

Hello,
i would like to know if it possible to get the CSS-class which is 
asigned to a button (for example)? I didn't find any 
documentation about this, just the function 
"getStyleContext().getProperty()", my current attempt:

Value value;
bArr[0].getStyleContext().getProperty("Class",StateFlags.NORMAL,value);


(bArr is an array of buttons).

I get the error, that 'Value' is not defined, if i use 'GValue' 
(as it is described here: 
https://developer.gnome.org/gtk3/stable/GtkStyleContext.html#gtk-style-context-get-property) i get 'function is not callable with GValue'

Any ideas? Thanks alot!