Connecting to an application rendering the following xaml:

<Grid

xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">

<Grid.Resources>

<Style x:Key="rectStyle" TargetType="Rectangle">

<Setter Property="Tag" Value="{Binding Tag, RelativeSource={RelativeSource Mode=TemplatedParent}}"/>

</Style>

</Grid.Resources>

<Rectangle Style="{StaticResource rectStyle}" Width="100" Height="50" Fill="Blue"/>

</Grid>