Button IsPressed Trigger Not Working - wpf

Question

I have a button with an undo image inside it.
I want the button to make the border appear when user clicks (ispressed) the button.
<Button Margin="0,7,12,0" HorizontalAlignment="Right" Height="20" Width="23">
<Button.Style>
<Style TargetType="{x:Type Button}">
<Setter Property="Background" Value="White"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type Button}">
<Border Background="{TemplateBinding Background}">
<ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center"/>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
<Style.Triggers>
<Trigger Property="IsPressed" Value="True">
<Setter Property="BorderThickness" Value="1"/>
</Trigger>
<Trigger Property="IsPressed" Value="False">
<Setter Property="BorderThickness" Value="0"/>
</Trigger>
</Style.Triggers>
</Style>
</Button.Style>
<Image Grid.Column="0" Grid.Row="0" Margin="0,0,0,0" Height="20" Width="20" Source="/Images/Undo.png">
<Image.Style>
<Style TargetType="Image">
<Style.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="Opacity" Value="0.7"/>
</Trigger>
</Style.Triggers>
</Style>
</Image.Style>
</Image>
</Button>
But its not working at all.
Any help will be appreciated!

Answer 1

I did the following changes to your style: 1) moved triggers within ControlTemplate; 2) assigned x:Name to Border so it can be referenced in the trigger; 3) defined BorderBrush.
<Button Margin="0" HorizontalAlignment="Center" Height="25" Width="75" VerticalAlignment="Center">
<Button.Style>
<Style TargetType="{x:Type Button}">
<Setter Property="Background" Value="White"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type Button}">
<Border x:Name="b0" Background="{TemplateBinding Background}">
<ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center"/>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsPressed" Value="True">
<Setter Property="BorderThickness" TargetName="b0" Value="1"/>
<Setter Property="BorderBrush" TargetName="b0" Value="Blue"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</Button.Style>
<Image Grid.Column="0" Grid.Row="0" Margin="0,0,0,0" Height="20" Width="20" Source="/Images/Undo.jpg">
<Image.Style>
<Style TargetType="Image">
<Style.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="Opacity" Value="0.7"/>
</Trigger>
</Style.Triggers>
</Style>
</Image.Style>
</Image>
</Button>

Answer 2

It's not working because the button template sets the border thickness to 1 directly, ignoring the border thickness attribute of the button element itself. You're successfully changing a value that isn't used.
You will have to copy and modify the button template if you want to change the border thickness.