Hi CSharpino,
Thank you for contacting Syncfusion support.
To set the visual style for all comboBoxAdv in your application in Office2013White, use this resource path:
“/Syncfusion.Themes.Office2013White.WPF;component/Tools/ComboBoxAdv/ComboBoxAdv.xaml”
We have prepared sample for the same. Please download the sample from the below link.
Regards,
Mariappan S.