Problem with style radiobutton, Cannot find resource named 'RadioButtonOuterEllipseFill'

[JMarcuss]

It already happens whenever I have a stackpanel and try to add a radiobutton from code-behind.

XAML:

C#:
RadioButton radioButton = new RadioButton();
stackpanel.Children.Add(radioButton);

Whenever I add it throught XAML alone it works, but only when the radiobutton isn't encapsulated within another component (like a groupbox or a stackpanel or a listview).

I want to be able to select multiple radiobuttons, that's why I want them in a listbox/view or a stackpanel.

Can anyone help?