Empty text box default text - wpf

Question

In my Window.Resources I have the following style:
<Style TargetType="TextBox" x:Key="HintText" xmlns:sys="clr-namespace:System;assembly=mscorlib">
<Style.Resources>
<VisualBrush x:Key="CueBannerBrush" AlignmentX="Left" AlignmentY="Center" Stretch="None">
<VisualBrush.Visual>
<Label Content="{DynamicResource EmptyText}" Foreground="LightGray" />
</VisualBrush.Visual>
</VisualBrush>
</Style.Resources>
<Style.Triggers>
<Trigger Property="Text" Value="{x:Static sys:String.Empty}">
<Setter Property="Background" Value="{StaticResource CueBannerBrush}" />
</Trigger>
<Trigger Property="Text" Value="{x:Null}">
<Setter Property="Background" Value="{StaticResource CueBannerBrush}" />
</Trigger>
<Trigger Property="IsKeyboardFocused" Value="True">
<Setter Property="Background" Value="White" />
</Trigger>
</Style.Triggers>
</Style>
If I use this for 1 TextBox with this,
<Label Content="Test" Foreground="LightGray" />
Test will show up in my TextBox if it's empty. When I try to use this style in different TextBoxes with this,
<Label Content="{DynamicResource EmptyText}" Foreground="LightGray" />
and
<TextBox.Resources>
<sys:String x:Key="EmptyText">Test</sys:String>
</TextBox.Resources>
it doesn't show anything. Is it possible to use this 1 style with a different string that is shown in the TextBox or do I have to make a different style for each TextBox?

Answer 1

You don't appear to be employing this style in any of the examples you give and it isn't at all clear what relationship your last XAML block has with the one before it.
However, yes you should be able to redefine EmptyText as often as you like. The Text property will be resolved in accordance with the Dependency Property value precedence rules.
So you can do something like this:
<DockPanel HorizontalAlignment="Stretch">
<DockPanel.Resources>
<Style TargetType="TextBlock">
<Setter Property="Text"
Value="{DynamicResource EmptyText/>
</Style>
<sys:String x:Key="EmptyText">Defined in the Dockpanel resource</sys:String>
</DockPanel.Resources>
<TextBlock/>
<TextBlock>
<TextBlock.Resources>
<sys:String x:Key="EmptyText">Defined in the textbox resource</sys:String>
</TextBlock.Resources>
</TextBlock>
<TextBlock>
<TextBlock.Resources>
<sys:String x:Key="EmptyText">Also defined at the textbox</sys:String>
</TextBlock.Resources>
</TextBlock>
</DockPanel>