WPF：怎么修改ToolTip里文字的字体和文字大小

WPF：如何修改ToolTip里文字的字体和文字大小？
求教了。。

[解决办法]
为ToolTip单独写样式

C# code

    <Style x:Key="Simple" TargetType="{x:Type ToolTip}">      <Setter Property = "HorizontalOffset" Value="50"/>      <Setter Property = "VerticalOffset" Value="50"/>      <Setter Property = "Background" Value="LightBlue"/>      <Setter Property = "Foreground" Value="Purple"/>      <Setter Property = "FontSize" Value="20"/>      <Setter Property = "FontWeight" Value="Bold"/>    </Style>