HandyControl/src/Shared/HandyControl_Shared/Themes/Styles/Dialog.xaml

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:hc="clr-namespace:HandyControl.Controls">

    <Style BasedOn="{StaticResource DialogBaseStyle}" TargetType="hc:Dialog"/>

</ResourceDictionary>