I have a textbox style that sets the Template property in order to add an animated watermark:
<Style
TargetType="{x:Type
TextBox}">
<Setter
Property="Template">
<Setter.Value>
<ControlTemplate
TargetType="{x:Type
TextBox}">
<Border
BorderBrush="{TemplateBinding
BorderBrush}"
BorderThickness="{TemplateBinding
BorderThickness}"
Padding="{TemplateBinding
Padding}">
<Grid>
<AdornerDecorator
Name="PART_ContentHost" />
&
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