How can I get a trigger to change the color of a TextBlock based on a DataContext Property?

Question

Why does the following code get the runtime error:

Members of the Triggers collection must be of type EventTrigger

But the Event

Answer 1

There is a typo as you did not close out Style.Triggers. And I found I needed to use the property TextBlock.Background. Thanks, you got me to the solution.

    <TextBlock.Style>
        <Style TargetType="{x:Type TextBlock}">
            <Style.Triggers>
                <DataTrigger Binding="{Binding Status}" Value="off">
                    <Setter Property="TextBlock.Background" Value="Red"/>
                 </DataTrigger>
            </Style.Triggers>
        </Style>
    </TextBlock.Style>

Answer 2

That is because you can only set event triggers directly on the Trigger property..

Use a style to achieve what you want:

<Style x:Key="Triggers" TargetType="TextBlock">
    <Style.Triggers>
        <DataTrigger Binding="{Binding Status}" Value="off">
            <Setter Property="TextBlock.Background" Value="Red"/>
        </DataTrigger>
    </Style.Triggers>
</Style>

The following objects have Triggers collections that can contain the trigger types listed:

FrameworkElement     Style, ControlTemplate, DataTemplate
----------------     ------------------------------------
EventTrigger         EventTrigger
                     Trigger or MultiTrigger
                     DataTrigger or MultiDataTrigger

Answer 3

You can do it in a style:

<TextBlock Text="{Binding Status}">
    <TextBlock.Style>
        <Style TargetType="{x:Type TextBlock}">
            <Style.Triggers>
                <DataTrigger Binding="{Binding Status}" Value="off">
                    <Setter Property="Background" Value="Red"/>
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </TextBlock.Style>
</TextBlock>