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

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

    <Style BasedOn="{StaticResource PoptipBaseStyle}" TargetType="hc:Poptip"/>

</ResourceDictionary>