how to change the visual state of a WPF control based on evaluation of other Visual Elements?

Question

I want to do the following:

<TextBlock Text="{Binding Result}">

I want to Color this based on an equality check on Result, what's the view centric way to do this? I remember reading about template selector, is that the right choice here?

example:

Text="Pass" Color="Green"
Text="Fail" Color="Red"

I'd like this to be dynamic so that if Text Changes it is re-evaluated.

Answer 1

You can use triggers inside a style:

<TextBlock Text="{Binding Result}">
    <TextBlock.Style>
        <Style TargetType="TextBlock">
            <Style.Triggers>
                <DataTrigger Binding="{Binding Result}" Value="Pass">
                    <Setter Property="Foreground" Value="Green" />
                </DataTrigger>

                <DataTrigger Binding="{Binding Result}" Value="Fail">
                    <Setter Property="Foreground" Value="Red" />
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </TextBlock.Style>
</TextBlock>

Alternatively you could create an IValueConverter implementation which converts strings to brushes (according to your rules) and use a binding directly:

<TextBlock
    Text="{Binding Result}"
    Foreground="{Binding Result,Converter={StaticResource my:ResultBrushConverter}} />

I won't go into details for this option because I think the pure-XAML option is the better way to go.