Question

MSDN says “Gets or sets an arbitrary object value that can be used to store custom information about this element.” which means I can store anything I want in this property.

But if you bind to this property (with property of type String having a value say “XYZ”) and use it in Trigger conditions it doesn’t work!

  <Trigger Property="Tag" Value="XYZ">
      <Setter Property="Background" Value="Red" />
  </Trigger>

It does not set the background red. You can try and assume myElement to be a TextBlock! Why is it like this?

Answer 1

Tag has no special functionality in WPF.

This works for me:

<TextBlock Tag="{Binding Data}"
           x:Name="tb">
    <TextBlock.Style>
        <Style>
            <Style.Triggers>
                <Trigger Property="TextBlock.Tag"
                         Value="XYZ">
                     <Setter Property="TextBlock.Background"
                             Value="Lime" />
                </Trigger>
            </Style.Triggers>        
        </Style>
    </TextBlock.Style>
</TextBlock>

And setting the Data object property to “XYZ” in an event.