XAMLでTextboxプレースホルダー表示

IsFocusedなしでvalueがない場合はプレースホリダーのように表示するメモ

<MultiDataTrigger>
  <MultiDataTrigger.Conditions>
    <Condition Binding="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type TextBox}}, Path=Text}" Value="" />
    <Condition Binding="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type TextBox}}, Path=IsFocused}" Value="False" />
  </MultiDataTrigger.Conditions>
  <Setter Property="Foreground" Value="#33000000" />
  <Setter Property="Visibility" Value="Visible" />
</MultiDataTrigger>

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